Suspension geometry analysis

[chevynut]

Since we have so many threads about different suspension geometries and the discussion is scattered and off-topic in a lot of them, I've started this thread to discuss the analysis of various suspension geometries and their differences. Please avoid off-topic posts here.

I want to focus on the C4 suspensions, stock tri5 suspensions, and a stock suspension with dropped spindles or cut springs, and taller balljoints. The claim has been made in the past that a stock suspension can be made to act and perform like a C4 suspension so we've been debating that for a long time. I want to prove or dispel any statements made to that effect. Clearly the stock tri5 suspension has deficiencies and it can be made better.

During this discussion I want to define "camber gain" as negative camber gain to avoid confusion. I want to define "spindle height" as the distance between balljoint centerlines. "A-arm length" is the distance from the center of the shaft to the center of the a-arm. A-arm "pivot" means the center of the a-arm shaft. "Level" a-arm means the a-arm pivot and balljoint are at the same height.

Early C4 suspensions are '84-87 and late are '88-96. The suspension geometries, both front and rear, were changed in 1988. Upper and lower a-arms and spindles (knuckles) are different in the front. The late front is about 1" wider than the early front. In the rear, the location of the strut rods at the inboard attach point was lowered in 1988. All link lengths are the same in the rear, early and late. The caliper mount was changed on the late suspensions making them a bit wider. The late rear is about 1" wider than the early rear.

To start this off, I decided to take some fairly careful measurements off of a tri5 clip I had cut off of a frame to do a C4 conversions. This allowed me to take things apart so I could take careful measurements. I even cut the balljoints apart to measure them so there would be no question of where the centers were, and it verified prior measurements. ;)

Here's what I found, and should be the basis for any calculations or CAD work to discuss these suspensions. If someone has what they think is better measurements, feel free to prove it. ;)

Stock Tri5 suspension measurements:

Upper a-arm shaft mounting width 29 3/4" front
Upper a-arm shaft mounting width 29" rear
Upper a-arm shaft centerlines (no shims) 28 3/8" (average front and rear)
Lower a-arm spacing 20 1/2"
Vertical spacing between upper and lower a-arm shafts, 10 1/2" front, 10" rear (at upper a-arm mounting holes)
Vertical spacing between upper and lower a-arm shafts, 10 1/4" (average at center)
Upper to lower balljoint centers 9 3/4"
Lower a-arm length 14 3/4"
Upper a-arm length 10 1/4"

Since the front and rear of the upper a-arms are not the same width or height, we should take an average of the dimensions as shown.

So with this information, we can lay out the stock suspension and analyze it. Right off the bat we can see that with the lower a-arm level, the upper a-arm is pointing down at the outboard end and is lower than the upper a-arm pivot by 1/2". We can also see that the upper a-arm pivot is 5" outboard of the lower a-arm pivot which is further than what has previously been reported here.

The question remains as to where "ride height" is as it pertains to a stock suspension, specifically the angle of the lower a-arm. There is a lot of information on the internet that indicates a lower a-arm should be level or slightly down at the outboard end.. The GM assembly manual shows the inner pivot to be at the same level as the lower balljoint, and with the a-arm level. Clearly to avoid tire scrub during suspension movement, the movement should center around a level a-arm. In fact, a level a-arm with some instantaneous negative camber gain would counteract that scrub as the suspension is compressed.

I'm assuming most of the discussion will be around static geometry, but you can infer dynamic effects from that to some extent. If anyone has suspension analysis software and can participate in this discussion, that would be awesome. So let's get to it. ;)

[chevynut]

I'm copying this stuff from the other thread that got taken off-topic. I corrected this to match my new measurements so don't use the numbers in the other thread.


.................................................. ..Tri5 ............Early C4 (84-87) .......Late C4 (88-96) ....Tri5, 1" taller balljoint
Spindle height (balljoint centers) .... 9.75................ 11.875....................... 13.375................... 10.75
a-arm pivot centers (vertically) ..... 10.25 .................10.84 .........................11.59 ..................10.25
Upper a-arm length (pivot to bj) ... 10.25...................8.25 .............................8 .....................10.25
Lower a-arm length (pivot to bj) .....14.75 .................13.25 ...........................15 ....................14.75

The net of this is that the C4 upper a-arm balljoints are above the pivot points. With the lower a-arm level, the upper a-arm angles down toward the center of the car.

[WagonCrazy]

Please define the years for "early C4" and "late C4". Just so we're all clear...

[chevynut]

As a reminder....

http://www.meganracing.com/uploadimage/dpage/2102011_174131.jpg
http://www.meganracing.com/uploadimage/dpage/2102011_174138.jpg


http://www.rqriley.com/images/fig-13.gif

http://www.actiontireco.com/images/steeringaxisinclination.jpg

http://www.jeepforum.com/forum/attachments/f96/1606785d1410812046t-wheels-offset-question-scrub2.jpg

[Rick_L]

I'm glad you took this discussion to its own thread. If nothing else, it will make searching for it easier in the future.

I was hoping to discuss some things tonight, but I was unable to get a proper layout using the dimensions above. One reason I hadn't posted previously was that I was unsure of my dimensions too. So hopefully tomorrow I'm going to take some measurements on my car, compare them to those posted, and correct my layout.

Edit: There are a couple of typos in your stock 55 dimensions. One is the average distance between the upper control arm shafts - s/b 29.375 not 28.375. Also in the dimensions for the extended ball joint, you left the spindle height stock, instead of +1".

2nd edit: Never mind on the spindle height for the extended ball joint, I was looking in the wrong place on the chart. It's correct.

[chevynut]

Edit: There are a couple of typos in your stock 55 dimensions. One is the average distance between the upper control arm shafts - s/b 29.375 not 28.375.

Rick, the 29.375 average is surface where the a-arm shafts are attached to the frame bracket. The shafts are about 1" thick and are attached to the inside of the frame brackets, so the CENTER of the shafts is at 28.375. That's the dimension without any shims.

Also, remember that the improvement that's supposed to "make a tri5 drive like a vette" is a 1/2" taller balljoint, not 1" ;). I put the 1" in the old thread to exaggerate the improvement using the taller balljoint. Let's first look at the 1/2" taller case.

Also notice that my NEW dimension for the vertical distance between upper and lower a-arm shafts has changed sightly from what is shown in the original chart. It's actually 10 1/4" at the center of the upper shaft instead of 10". I'm going to edit that in the chart to avoid confusion.

[chevynut]

Ok I did a layout of the a-arm pivots and balljoints using the dimensions I got yesterday and something wasn't right. When laid it in CAD I got a SAI that was backwards, i.e. the steering axis is pointing inward at the bottom at about 8.5 degrees. That can't be right :(. The stock SAI is specified at 3 1/2 to 4 1/2 degrees. So something was wrong with one or more of the dimensions above.

I'm pretty confident in the upper a-arm shaft mounting width (just re-checked it). I re-checked the a-arm lengths and got slightly different measurements this time. I don't know why it's so hard to measure these things, but the balljoints make it a little difficult. I used the a-arms where I removed the balljoints to measure instead of using the stud. I had cut the upper balljoint apart so it was easier to get an accurate measurement of the ball center. I also used the balljoint hole in the lower a-arm to get that length. I got 10 1/4" for the upper a-arm length, and 14 3/4" for the lower one.

I also decided to re-measure the lower a-arm pivot width on my intact 56 sedan. I took the lower a-arms off the clip before I measured them and probably should have put them back on. I tried to estimate using the lower a-arm shaft bolts and thought that would get me close enough. This morning I measured 20.5" on my sedan, between centers of the shaft bolts by using a square from the floor to the bolt centers and marking them on the floor. Don't know how I could have been so far off. :confused: I did notice the shaft centerlines are NOT centered between the bolt holes. ;) I corrected the post above with this new measurement. Please feel free to check any of these measurements yourself to make sure I didn't screw up.

Using these measurements I now get a SAI of 3.39 degrees in the right direction, so these measurements look good. With a couple of shims it would be in spec. You can't do an analysis with bad dimensions ;). I corrected the info above again.

http://www.trifivechevys.com/attachment.php?attachmentid=5722&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=5723&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=5724&stc=1

[Rick_L]

The backward SAI was what I got when I laid out your dimensions. Also the SAI is 3.5 degrees, it is not variable. I've seen that 3.5-4.5 degrees somewhere previously, someone didn't get it. I think the layout should be done using 0 camber and 3.5 degree SAI as a starting point. Then the variable determined from the layout will be the horizontal location of the upper control arm shaft, which is more or less what it is in the real world as that's where you shim to get camber.

I'll go back and do what I said last night, and also look at what the new info does.

[chevynut]

Here's one more piece of information on a stock suspension that may help with the analysis. The stock 6.70-15 tire rolls 755 revolutions per mile per GM 56 Chevy specs. That means the rolling radius is 13.36". Also, at stock height these are the suspension dimensions from GM. Note they show the lower a-arm level in this drawing, which may not be accurate.

http://www.55-57chevys.com/tech/56/3-5.gif

[chevynut]

To get more good data I've taken very careful :) measurements again on the C4 suspension dimensions. I actually dissected an upper balljoint to get the spindle lengths...I assumed the lower balljoint was the same length since I didn't have one to dissect. The bare spindles are 9 5/8" tall for the early suspensions, and 11 1/8" tall for the late suspensions (they're probably metric). I measured the upper balljoint center at about 1 1/8" above the spindle. I also re-measured the pivot centers as carefully as I could. The upper pivot center measurement is off of my recently assembled Nomad frame. I measured the shaft centers in front and back, and averaged them to get the center distance. The upper to lower measurement was taken off of my frame too, using the floor as the datum and measuring up to the center of the upper a-arm shaft (averaging front and rear measurements) and measuring from the floor to the lower pivot holes. I put rods across the a-arm shaft holes on an early and late k-member and found the difference in height to be exactly 3/4", which is what I measured before.

Here are some new measurements:

.................................................. ...................Early C4 ('84-87) ............Late C4 ('88-96)
Spindle height (@ balljoint centers) ....................... 11.875..............................13.375 (assuming 1 1/8" balljoints)
a-arm pivot centers (vertically) ...............................10.84 ..............................11.59 (3/4" difference in height measured)
Distance between upper a-arm pivots (center)..........30.00........................... ....30.00 (with 1/4" shims each side)
Distance between lower a-arm pivots.......................24.125............... ..............24.125
Upper a-arm length (pivot to bj) .............................8.25 .................................8.00
Lower a-arm length (pivot to bj) ............................13.25 ................................15.0

I corrected the table in the previous post above for these measurements to avoid confusion.

[chevynut]

Rick, I got close to the right SAI with my new dimensions, mostly confirming their accuracy. It's a little less than 3.5 degrees but with a couple of shims it would be right on. Actually the SAI is variable, if you define it to the ground so maybe that's why they specify a range in the specs. Every reference I've seen for SAI shows it from "true vertical" not relative to the spindle.

http://motorarticles.freehostia.com/images/wheel%20alignment%20theory%20operation_img_5.png

I agree that it might be best to fix the lower a-arm, locate the upper balljoint at the 9.75" and 3.5" SAI, and then locate the upper a-arm pivot from there. That will eliminate any ambiguity regarding shims.

Here's where the SAI is shown as 3.5-4.5 degrees: http://chevy.oldcarmanualproject.com/chevyresto/56031.htm

[chevynut]

A little more info....from the center of the stock tri5 lower balljoint it's 2 13/16" up to the center of the spindle. Also, the tri5 wheel mounting surface is 4 7/8" outboard of the lower balljoint. The stock wheel has +9/16" offset and the front track width is 58". This with the 13.36" rolling radius will help locate the tire contact patch.

(edited balljoint to spindle dimension)

[chevynut]

Using all the stock measurements, here's what my CAD layout shows for a STOCK tri5 (55-56 tire dimensions) with the lower a-arm level.

The front suspension instant center is located 215.78" from the car's centerline on the same side as the tire in question. This puts the stock roll center at 1.61" below the ground at the center of the car.

My 56 sedan appears to sit at a bit higher than stock height based on the lower a-arm pivot height around 10.5". I have read that the CG should be about at the camshaft centerline, which looks to be about 20-22" above the ground on my car, as good as I can measure it. I'll call it 21" for this discussion unless someone has better data.

[chevynut]

I just looked at the scenario using a stock spindle with 1/2" taller upper balljoint, and a lower a-arm that's level, 1" and 2" above level at the lower balljoint. These are all STARTING POINTS with the camber set to zero. The car is assumed to be at ride height in each situation.

For the level lower a-arm, the instant center is at an infinite distance from the center of the car because the top and bottom a-arms are both level. The roll center is indeterminate (no instant center) but will be somewhere at or very slightly above ground level. I'm assuming camber is zero in this case.

For the 1" off-level (up) a-arm, the instant center is 341.05" from the center of the car on the opposite side of the car. The roll center is 1.05" below the ground at the center of the car.

For the 2" off-level (up) a-arm, the instant center is 177.26" from the center of the car on the opposite side of the car. The roll center is 1.83" below the ground at the center of the car.

I have not yet looked at camber curves for any of these situations.

[Rick_L]

Ok I've crunched several scenarios on stock based suspensions and think I've learned a bunch. I used Chevynut's latest dimensions which make sense.

Here's a summary of my results.

Roll center height
Stock -1.63
Stock w/ 2" spring drop -4.02
Dropped spindle -1.20
Extended ball joint w/ 2" spring drop -1.07
C3 spindle w/ 2" spring drop -0.8
Dropped spindle + extended ball joint 0.96

Roll moment arm
Stock 22.63
Stock w/ 2" spring drop 23.02
Dropped spindle 19.47
Extended ball joint w/ 2" spring drop 19.34
C3 spindle w/ 2" spring drop 19.07
Dropped spindle + extended ball joint 17.31

Camber gain in next 1" compression travel
Stock -0.21
Stock w/ 2" spring drop -1.00
Dropped spindle -0.21
Extended ball joint w/ 2" spring drop +0.69
C3 spindle w/ 2" spring drop +0.77
Dropped spindle + extended ball joint +0.33

I used Cnut's suggested 21" CG height for the initial setup, then let it move with the lowering. I think that's maybe low because what we're talking here is sprung CG not overall. Sprung is going to be a bit higher because all the unsprung is down low. But it's the same for all examples so you can see the trend.

Except for the stock and stock w/ 2" spring drop listing, I used the rolling radius Cnut posted for a 225/50/17 tire.

I think ride height could be investigated some more. I used a level lower arm for "uncut" springs.

I realize I should have made a table in Word or Excel and imported it, hard to read what I posted. Will do tomorrow. I've put too much time in it today already to fix it now.

What I see is that drop spindles get you better roll center and roll couple moment arm than other choices. The extended ball joints or C3 spindles get you more camber gain and improve the roll center a little, assuming lowering with cut springs. The combination of drop spindles and extended ball joints is an interesting mix.

The main benefit of the C3 spindle is the scrub radius. That and an easy way to get 12" rotors and big calipers. Otherwise the results are similar to a 1" extended ball joint, which I expected. I guess you can consider whether an extended ball joint is strong enough but it probably is.

As I've always said, the drawback to 2" lowering springs is the reduced travel.

I'm going to put mine together with the C3 spindles/brakes and see how the suspension travel deal works out, as well as seeing whether I'm happy with ride height. If I'm not satisfied, it's pretty obvious which way to go.

Edit: I made an attempt to make the data more readable.

[rockytopper R.I.P 5-13-2017]

Please present data to support assumptions that stock trifives have level lower arms other than cartoons that are assumed.

[Rick_L]

I'm waiting for you to do that. Will I have to wait a long time?

[rockytopper R.I.P 5-13-2017]

I'm waiting for you to do that. Will I have to wait a long time?
I will help you to determine it yourself. If the arm is horz at stock ride height then my car setting in my shop at curb weight at least 2 inches down from stock is defying the laws of phyics. Do either of your models that are now perfectly correct per the fame gm diagram have the ground line 9.5 -10.49 below the lower pivot? I bet not.....

[chevynut]

I laid out the early C4 geometry this morning and it all seems to work out fairly close. I located the lower a-arm pivot and balljoint, set the SAI at 8.744 degrees (not sure that's right), and located the upper balljoint. Then I worked back and got the inner pivot using the upper a-arm length. The distance between the upper a-arm pivots came out to 30.6" which is a bit wide but close to what I measured on my late suspension. With a little negative camber it would be closer. My C4 "Vette Specs" book says the camber should be "0.8, +/-0.5 degrees" for all years. Does positive camber make any sense? I would have thought it should be -.8 degrees so it must be a typo...on every page :eek:.

The late C4 is another story. I laid out the 15" lower a-arm using the same lower pivot point since early and late lower pivot spacings are the same. Then I located the upper balljoint using the spindle height and the same SAI of 8.744 degrees (from my specs book). After locating the upper a-arm pivot, I ended up with over 34" between upper pivots which is over 4" too wide :confused:. If my measured dimensions are correct, then the late suspension SAI must be a lot more to end up at 30" between upper pivots as I measured on my Nomad chassis. So I used my digital level on my Nomad spindle and found that the SAI for the late suspension is actually closer to 18 degrees per my measurement!!! If I use my measured 30" at the upper pivots, SAI turns out to be 18.04 degrees so it all works out. I'm surprised there's that much SAI on the late C4 spindle. :eek:

Also, the center of the early hub is 5 5/8" above the lower balljoint and the wheel mounting surface is 5.25" outboard of the lower balljoint, with the disc installed. The center of the late hub is 5 3/4" above the balljoint and the wheel mounting surface is 4" outboard of the balljoint. The tires are 245/45-17 which roll 810 revs per mils (BFG G-Force Comp T/A). That makes the rolling radius 12.45".

To validate the measurements above I added the lower a-arm lengths and the balljoint to WMS distance to get 18.5" (13.25+5.25) total for the early suspension, and 19" (15+4)for the late suspension verifying the 1/2" difference that I've measured in WMS width. So everything seems to be checking out. ;)

[Rick_L]

18 degrees doesn't sound right at all. Does your layout let you measure scrub radius? Is it close to zero with the layout you have?

The 8.75 degree SAI with the early suspension is a bunch more like I expected.

[chevynut]

Using all the C4 dimensions above, and with a level lower a-arm I calculated the instant centers and roll centers.

For the early C4 suspension I get an instant center of 83.80" from the center of the car and a roll center 3.149" ABOVE the ground.

For the late C4 suspension I get an instant center 66.42" from the center of the car and a roll center 3.792" ABOVE the ground.

Both of these suspension geometries move the instant center a lot closer to the center of the car than the stock tri5 geometry and the roll center is quite a bit higher (~5"!!) as a result...which is a good thing for handling. It's around 3 1/4-4" higher than using the 1/2" taller balljoint. If you start with a lower a-arm pointing DOWN 1" at the outboard end, the roll center is even higher, but the CG rises 1" too. I may look at that scenario.

Another thing you can see from these layouts is that a shorter tire lowers the CG of the car, lowering the instant center the same amount, but the roll center doesn't drop that much.

[chevynut]

18 degrees doesn't sound right at all. Does your layout let you measure scrub radius? Is it close to zero with the layout you have? The 8.75 degree SAI with the early suspension is a bunch more like I expected.

I agree Rick, but I measured The SAI on my late Nomad spindle with my digital level. It's right at 18 degrees according to my layout and my level. My layout doesn't work out if I use the 8.744 degrees of the early spindle. The scrub radius on the early suspension is 3.34" and on the late one it's basically zero using the 18 degree SAI on my layouts.

Here's the two spindles (late on the left) with the hub faces sitting parallel...the difference in SAI is readily apparent. This is news to me. ;)


http://www.trifivechevys.com/attachment.php?attachmentid=5731&stc=1

[chevynut]

I just put the late spindle and hub on my level welding table, studs down, and put a 1/2" rod through the balljoint stud holes. The SAI is indeed 18 degrees per my angle finder. ;)

But I realized I made a mistake on the scrub radius....I used the wheel mounting surface, not the center of the tire as the contact point. The wheels have a 50mm positive offset. I'll have to re-do the roll center slightly too, but it won't make much difference. I'll edit the numbers above.

So with the 50mm offset I get 1.37" scrub radius for the early suspension, and a NEGATIVE 2.02" for the late one.

What does a negative scrub radius do?

"Positive and negative scrub radii have benefits in different types of suspension. A MacPherson strut assembly typically performs well with a lot of SAI and caster, a system negative scrub works well in. Because both SAI and caster increase the amount of camber on the outside wheel when steering, the fulcrum pivot point is at a point that has more leverage, requiring less steering effort. Negative scrub also helps reduce torque steer in front wheel drive cars. Positive scrub radius works well with suspensions that use dual control arms that use less caster and SAI to optimize geometry.

As with anything else, a little of a good thing is great, but lot of a good thing is not necessarily better. When you have excessive scrub, whether it be positive or negative, steering effort increases and road 'feel' increases, as the steering is more susceptible to road shock. Additionally, if you plan on doing some homework on, and modifying your scrub radius, you must take into account the amount of sidewall flex your tire will encounter under hard cornering. When the sidewall flexes, the contact patch moves in relation to the SAI and can make a slightly negative scrub radius become zero."

[Rick_L]

A comment on stock ride height and my layouts/calculations, especially to rocky.

My layout has the stock lower control arm centerline at 10.36" above the ground. According to the 55 assembly manual, section 3, sheet 5, the lower control arm centerline is 11.0" at "curb weight" and 10.00" at "design load".

Since I looked at "stock height" and 1" and 2" lower than stock height (by my definitions), to me the 10.36" dimension is probably as accurate as some of the other measurements/assumptions. rocky, didn't you mention a 10.49" dimension?

Since we're looking at trends and trying to see what happens with certain changes, as well as comparing to other designs, I don't see any need to revise anything based on what the stock ride height is.

If someone wants to see results at some other ride height, I can do a couple more layouts if there is real interest. But they will just fill in the gaps so to speak.

[rockytopper R.I.P 5-13-2017]

A comment on stock ride height and my layouts/calculations, especially to rocky.

My layout has the stock lower control arm centerline at 10.36" above the ground. According to the 55 assembly manual, section 3, sheet 5, the lower control arm centerline is 11.0" at "curb weight" and 10.00" at "design load".

Since I looked at "stock height" and 1" and 2" lower than stock height (by my definitions), to me the 10.36" dimension is probably as accurate as some of the other measurements/assumptions. rocky, didn't you mention a 10.49" dimension?

Since we're looking at trends and trying to see what happens with certain changes, as well as comparing to other designs, I don't see any need to revise anything based on what the stock ride height is.

If someone wants to see results at some other ride height, I can do a couple more layouts if there is real interest. But they will just fill in the gaps so to speak.

Rick the 10.49 came from the diagram that is posted in the other threads as dimension A height at curb weight which is what should be used in these analysis sense cars are aligned at curb weight not design weight an assumption on my part. So if 11 is a true number then so be. It would only make the bottom arm point down more. If your model shows the tire contact patch touching the ground with cnuts tire specs and lower arm level then something is wrong with your layout. If 11 inches is the real number then my car is dropped close to 3 inches from stock. My dimension A measured at curb weight is approx 7.7 -7.8 measured. I just went out and jacked the car up up to put the lower pivot 10.38 and the lower arms are pointing down at least 5 degrees. It is looking like if I had cut less coil and stay closer to 2 inch drop my arms would have ended up almost level and not .56 high on outbd. Any how I think ride height is very inportant. When you guys correct the assumpton that the lower is level at stock ride height your analysis will change alot for the worse. I still haven't gotten a clear answer of how to determine roll center when ic is on wrong side like stock trifive is. Some show you still run the line to the tire patch center but the link I shared and we discussed about F1 says that in this case you create a bisecting line between the to arm lines and project that back to the center to determine roll center in that case. Still lots of conflicting info about this case.

[Rick_L]

You need to remember that the lower ball joint center is pretty close to the top of the control arm, while the shaft center is in the middle of the control arm. Plus the arm is curved on the bottom. This gives the illusion that the arm is going down from shaft to ball joint even at stock ride height.

As for your question about the location of the roll center when the instant center is outboard, I explained that in the other thread.

Not sure what's really agitating you as the analysis shows that the extended ball joints do what's claimed. Are you have a tough time accepting that the dropped spindles do what they do? Or do you think that the extended ball joints do more than what I said? Also the extended ball joints do move the instant center to the supposed "good" side, as does the C3 spindle, which is essentially the same thing. I can post the I.C. locations if that would help, I edited them out. They were in the unedited post but you probably couldn't match them up to the various conditions because of the presentation.

How much wheel travel do you have in bump with the 7.7" dimension? Can't be much.

[rockytopper R.I.P 5-13-2017]

Rick I believe the lower ball joint attaching bolts front and back are approx .5 below the pivot give or take. My lower arms are straight tubular no curve my level measues at least 5 degrees down at stock ride height jacked to 10.38 dimension A. My approx ball joint Measures approx 9 in or so from floor. The lower arms are clearly not level at stock ride height. This has been the bases for both of you guys argument against what I have stated in ever discussion. If they were truely level in stock form I would have never ever argued my case or called drop spindles junk. If you or C'nut cannot accept the fact that the arms are not horz at stock height then we will always have a stalemate about this topic. Once you agree I'm correct about the lower arm being down we can then all get on the same page. If the arm is level at stock ride height I'll eat every word todate.
I did not join in hear again when I said I wasn't to start more bs. We just need to get the real truth out. So no I'm not nick picking your statements.
Rocky

[rockytopper R.I.P 5-13-2017]

As for your other question measuring the rubber bumper on my tube arms about 1-1/2. Jacked to 10.38 little less than 3. How much travel per spec does stock have?

[Rick_L]

rocky, I don't think it really matters where the stock lower arms start out.

The results are going to be similar, maybe even worse. I can do a layout with the lower arms where you say and show this. Will post tomorrow.

[rockytopper R.I.P 5-13-2017]

Rick when you do the camber goes postive from the get go what I have always said. This is not good for handling. Any thing below level is going positive from the start of travel using the trifive data points you have. I'm not disputing any of cnuts measurements of the individual parts I assume all are correct except the upper pivot delta close to 5 mine at least in my case 4ish with the arms I have. Do we agree on it will go postive below level? If so that has always been my argument against drop spindles because they keep the same postive curve as stock. It does not correct for the better.

[rockytopper R.I.P 5-13-2017]

What angle do you guys have for the relation between lower and upper oem stock arms based on your model? My model says they intersect on the wrong side way below ground because I argue the bottom arm points down and out board. If I concur with your assumptons and use your criteria to define roll center. The ic has to same height as lower arm. A line passed back thru the contact if arm is horz stock would be below ground. Lower than my case shown even with my arm pointing up hill above horz.

To also get on same page here using your criteria what is the height in your models of the lower ball joint from ground using oem tire for comparison. This does not change much relatively speaking with ride height changes agree?

[Rick_L]

It's not clear to me what you want, or what it proves or disproves.

[rockytopper R.I.P 5-13-2017]

Rick I am simply saying if your static model used to analysis math does not add up then your results and findings will also not add up and are therefore in error. With the arm pointing down at stock ride height it clearly discounts everything you and Cnut have stated all along and has been the source of our disputes and why we 3 cannot agree on this. Thats all I'm saying.
Rocky

[Rick_L]

The lower ball joint is at 10.36" from the ground in my stock layout. This comes from the tire having a 13.36" rolling radius and the lower ball joint being 3" down from the spindle centerline, which was what Cnut posted.

You're right, if the lower control arm is horizontal, then the roll center has to be below ground level.

[chevynut]

Here's a summary of my results.

Roll center height
Stock -1.63
Stock w/ 2" spring drop -4.02
Dropped spindle -1.20
Extended ball joint w/ 2" spring drop -1.07
C3 spindle w/ 2" spring drop -0.8
Dropped spindle + extended ball joint 0.96

What lower a-arm orientation are you assuming here? It makes a big difference. It's interesting that a dropped spindle alone with no other changes raises the roll center from stock slightly. Did you do the 1/2" taller balljoint alone? I think that makes the upper and lower a-arms parallel when the lower one is level.



Camber gain in next 1" compression travel
Stock -0.21
Stock w/ 2" spring drop -1.00
Dropped spindle -0.21
Extended ball joint w/ 2" spring drop +0.69
C3 spindle w/ 2" spring drop +0.77
Dropped spindle + extended ball joint +0.33

This is an interesting outcome. I'm assuming you started with the lower a-arm level here except for the case of the dropped springs. The starting point affects the results. What lower a-arm orientation did you assume with the dropped springs?


I think that's maybe low because what we're talking here is sprung CG not overall. Sprung is going to be a bit higher because all the unsprung is down low. But it's the same for all examples so you can see the trend.

I don't think the actual CG height is as important as comparing the roll moment arms. That's why I tried to specify a CG location to use.


Except for the stock and stock w/ 2" spring drop listing, I used the rolling radius Cnut posted for a 225/50/17 tire.

I don't recall posting that. I posted rolling radius for a 6.70-15 and a 245/45-17 tire. Let's stick with those two tire sizes for this analysis unless we want to add one specific tire for a modified stock suspension. What radius did you use?



What I see is that drop spindles get you better roll center and roll couple moment arm than other choices. The extended ball joints or C3 spindles get you more camber gain and improve the roll center a little, assuming lowering with cut springs. The combination of drop spindles and extended ball joints is an interesting mix.

Thisi s precisely why I say dropped spindles and taller balljoints are better than cut springs and taller balljoints. You get the lowering of the CG without sacrificing roll center and camber gain.


As I've always said, the drawback to 2" lowering springs is the reduced travel.

I still believe that if the lowering springs result in a lower a-arm angled upward at the outboard end, you increase tire scrub as well as losing camber gain. Clearly camber gain is improved if the lower balljoint moves outboard, as it would in that case. If the lower balljoint moves inboard, it decreases camber gain. That's what happens if the lower a-arm is pointing up at the outboard end. The question though is what happens to the upper a-arm.

Good discussion so far, but I think we need to be very careful with our assumptions before we summarize everything, and make sure we specify the exact starting points (zero camber, car at ride height). I'd like to look at these scenarios as starting points with camber gain, roll centers and roll moment arms over 3" of travel....1" above ride height, ride height, 1" compressed, and 2" compressed:

Starting points:

Stock suspension with lower a-arm pointing DOWN and lower balljoint 1" below pivot (assumed stock configuration).
Stock suspension with lower a-arm level.
Stock suspension with lower a-arm pointing up and lower balljoint 1" above pivot (cut spring).

Stock suspension, 2" dropped spindles, with lower a-arm pointing DOWN and lower balljoint 1" below pivot (assumed stock configuration).
Stock suspension, 2" dropped spindles, with lower a-arm level.
Stock suspension, 2" dropped spindles, with lower a-arm pointing up and lower balljoint 1" above pivot (cut spring).

Stock suspension, 1/2" taller balljoint, with lower a-arm pointing DOWN and lower balljoint 1" below pivot (assume stock configuration).
Stock suspension, 1/2" taller balljoint, with lower a-arm level.
Stock suspension, 1/2" taller balljoint, with lower a-arm pointing up and lower balljoint 1" above pivot (cut spring).

Stock suspension, 2" dropped spindles, 1/2" taller balljoint, with lower a-arm pointing DOWN and lower balljoint 1" below pivot (assume stock configuration).
Stock suspension, 2" dropped spindles, 1/2" taller balljoint, with lower a-arm level.
Stock suspension, 2" dropped spindles, 1/2" taller balljoint, with lower a-arm pointing up and lower balljoint 1" above pivot.

Stock suspension, 1" taller balljoint, with lower a-arm pointing DOWN and lower balljoint 1" below pivot (assume stock configuration).
Stock suspension, 1" taller balljoint, with lower a-arm level.
Stock suspension, 1" taller balljoint, with lower a-arm pointing up and lower balljoint 1" above pivot.

Early C4 suspension with a-arm pointing down at the outboard end and balljoint 1" below pivot.
Early C4 suspension with a-arm level.

Late C4 suspension with a-arm pointing down at the outboard end and balljoint 1" below pivot.
Late C4 suspension with a-arm level.

It looks like a lot of work but I don't think it's that much ;). I'm pretty sure we have all the correct dimensions now, so let's not deviate from that. Let's assume the 21" stock CG height for the sake of comparison only.

Edited to add 2" dropped spindles in 2 scenarios. We need to compile a table of these results. ;)

[chevynut]

Please present data to support assumptions that stock trifives have level lower arms other than cartoons that are assumed.

Let's take the GM specs as being true, unless you have other data. I'm using this page:

http://www.55-57chevys.com/tech/56/3-5.gif

GM says the lower a-arm pivot is 11" above the ground at curb weight. The 6.70-15 tire rolling radius is 13.36" per the calculations I did above. The spindle is 3" above the lower balljoint. That puts the balljoint at 10.36" above the ground at ride height and curb weight (no driver). So according to GM, the lower balljoint is .64" BELOW the pivot. That's close to level, but "slightly" low on the outboard end, which I have said is probably ideal.

Do you agree with that?

If so, your 2" drop would put the lower balljoint at 1.36 ABOVE the pivot at ride height. Agree?

[chevynut]

Rick the 10.49 came from the diagram that is posted in the other threads as dimension A height at curb weight which is what should be used in these analysis sense cars are aligned at curb weight not design weight an assumption on my part.

That 10.49" dimension is for a 57 that has smaller 14" tires. It's 11" for 55-56.

[Rick_L]

Chevynut, long reply, I may miss something in reply, but I'll try not to.

My starting point was a level lower arm. The 2" drop spring has the inner end of the lower arm 2" lower than the outer. All the numbers shown were done the same way. Again, they were - Stock, 2" spring drop, 2" drop spindle with no spring drop, 1" extended ball joint with 2" spring drop, C3 spindle with 2" spring drop, and dropped spindle with 1" extended ball joint. I didn't figure anyone was going to do an extended ball joint or C3 spindle without some kind of lowering.

All the different configurations started at 0 degrees camber. The only thing reported was camber gain. The camber gain is going to be virtually the same no matter what reasonable static camber is used.

I used the rolling radius for the 245/45-17 tire that you posted, 12.63". I mistakenly thought it was a 225/50-17. Looks like a 225/50-17 would be 0.25" shorter. Close enough for me.

I didn't do a 1/2" extended ball joint. I can't recall ever seeing one for sale. Regardless, the results for that case will be in between the others shown.

I did some of your other cases, but reporting all that was clumsy initially, and still is somewhat. Thing is all the stock pivot location setups move in similar relationships to the ones posted - so I didn't post too many. Some of the other cases would require fabbing new pivot locations and new control arms, you might as well use a C4 suspension or something like an AME if you want new pivot points.

I may do the C4 stuff when I get time. I'd be interested in doing the AME too but I've never seen those numbers published.

[rockytopper R.I.P 5-13-2017]

I'm going to formally appoligize Laz. I was wrong for previously calling you a coward. Hope you will except that.
I do agree with your statements above directed at me. My measurement on my on car are saying that also after re measuring today and looking at what Rick was stating. I was wrong all along on the height of the lower ball joint after looking at one laying out the pivot center is .75 to .875 from the mounting hole I stated 1/2 above. So yes I'm on board with your data points. I'M going to go back and correct my lay out. I just recieved this info it also backs you up.
http://chevy.oldcarmanualproject.com/shop/1955/55csm0307.html see note 5

Can you please post a sketch like I did before that shows arm lengths and the delta relations of the pivot locations you guys are using so I may insure my layout is correct. compare to real measurements on my setup. My upper pivot is fixed and appears to be 4 inches outbd of lower. I thank you are now saying 5?
Thanks
Rocky

[rockytopper R.I.P 5-13-2017]

Nevermind request for sketch after reading your last inputs on stock data points I'm going to agree with average as you stated. But I am having issues with your spindle length pivot to pivot. As I state above my lower ball joint height was off by .75 to .875. But if I deduct that from my layout showing 11.75 I get a 11- 10.875 length with 1/2,taller ball joint. Based on this photo I just took using the top of the ball joint plate as its pivot. The length from bottom thread or nut top is 2 inches. The nut top equals the bottom of the spindle loaded so the lower ball joint pivot is 2 inch above the bottom spindle surface. Do you guys agree?

http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_165.jpg

[rockytopper R.I.P 5-13-2017]

Here is my layout from before its wrong. I'll also add using the lower ball joint data stated above implies the lower ball joint may be slightly more than .68 below horz maybe .87 but no need to argue this is mute in the big picture. Can we agree on spindle height pivot to pivot? With 9.75 stock would only be 10.25 my measurements say otherwise.

http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_122.jpg[/QUOTE][/QUOTE]

[rockytopper R.I.P 5-13-2017]

This is a screen shot of my corrected layout using C'nut data points accept I set stock spindle height at 10.5 and lower ball joint .875 down at stock ride height. The light blue is stock and stock with 1/2 taller ball joint. The minute you put a 1/2 inch taller ball joint on the IC moves to the correct side of car. This guys is why adding it is so dramatic for the better with no other change. I don't believe the assumpton if its on wrong side is really ok from a handling stand point. The red represents 2 inch drop springs. You will note a dramatic change in the suspensions arc travel. The delta in the spindle axes between them is .63 degrees. The roll center appears to be inch above ground with 2 inch drop springs. I will guess Cnut but when you run the c4 numbers it will have more if a negative camber gain trend like the drop spring does on stock trifive with taller ball joint. I'm not saying better one just saying I bet C4 has a negative gain. The stock trifive or stock with drop spindles will have less negative more positive. I'm just guessing here have done no c4 analysis.

http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_166.jpg

[rockytopper R.I.P 5-13-2017]

This is very good info about alignment something I have always said is very important in this dicussion. Note what it says on top of page 4 about camber setting old train of thought vs today. This also matches what mine is set at listed many times close to C4 or c5 settings give or take. You get increased handling and stability.
http://www.valleyofhastings.com/WheelAlignment2.pdf

[chevynut]

I will help you to determine it yourself. If the arm is horz at stock ride height then my car setting in my shop at curb weight at least 2 inches down from stock is defying the laws of phyics. Do either of your models that are now perfectly correct per the fame gm diagram have the ground line 9.5 -10.49 below the lower pivot? I bet not.....

I'm getting behind you guys with the follow-ups. ;) Nothing is defying the laws of physics.....

Your car is not at stock "curb weight" with the LS engine and probably some other mods. What is the actual weight of your front end?

One other thing to note is that a 1/2" taller balljoint only makes the upper and lower a-arm PARALLEL (i.e. upper a-arm is level) when the lower a-arm is level. The upper a-arm barely goes out of parallel with the lower one as the suspension is compressed 1-2". I think this has minimal effect on camber gain, but I will look at it more closely.

[rockytopper R.I.P 5-13-2017]

Laz please ignore that reply I made to Rick I was wrong and delete you response its off topic at this point. Then read my post today I'm agreeing with you mostly accept on spindle height. Please Read what I posted then respond.
Rocky

[chevynut]

If 11 inches is the real number then my car is dropped close to 3 inches from stock. My dimension A measured at curb weight is approx 7.7 -7.8 measured.

11" at dimension "A" is the correct distance from the ground to the lower a-arm pivot at ride height and curb weight for a 55 or 56 using a 6.70-15 tire.

Here's my calculations for your suspension drop.

Let's call your dimension "A" 7.75" since that's in the middle of your range. I believe you have a 255-45/17 Kumho tire based on a picture on your Nomad thread. Kumho says that size tire rolls 796 revolutions per mile, so the rolling radius is 12.67". Subtract 3" from that and the lower balljoint is at 9.67" off the ground. So your lower balljoint is 1.92" above the a-arm pivot. The stock stance puts the lower balljoint at .64 BELOW the pivot as calculated from GM specs. So your car is dropped 2.56" from stock per these calculations. Sound right?


I just went out and jacked the car up up to put the lower pivot 10.38 and the lower arms are pointing down at least 5 degrees.

That's kind of irrelevant because your tire is shorter than stock. Also, you need to look at where the balljoint and pivot are, not the face of the a-arm.


When you guys correct the assumpton that the lower is level at stock ride height your analysis will change alot for the worse.

My calculations show the balljoint .64" below the pivot in stock configuration. That's not a big change, especially since it's so close to level. So nothing will get "a lot" worse....in fact the roll center will rise because the instant center drops as the balljoint falls relative to the pivot. But the car rises too.


I still haven't gotten a clear answer of how to determine roll center when ic is on wrong side like stock trifive is. Some show you still run the line to the tire patch center but the link I shared and we discussed about F1 says that in this case you create a bisecting line between the to arm lines and project that back to the center to determine roll center in that case. Still lots of conflicting info about this case.

You do it the same way as you do with the instant center on the opposite side of the car. You draw a line through the a-arms and it intersects outboard of the car on the same side as the suspension. Then you run a line from the instant center through the contact patch of the tire that's on the same side of the car as the suspension you're looking at, and extend it to the center of the car. I saw a diagram of it somewhere.

[rockytopper R.I.P 5-13-2017]

Again please delete I was wrong read my latest responses lafter you ask if I agree with you lol.

[chevynut]

Rocky, I finally caught up and I accept your apology.:) I'm really not trying to attack your plan, just understand what the mods you made really do.

Also, you seem to keep mis-stating what I've been objecting to. You say 2" dropped spindles are "junk" and prefer 2" dropped springs for some reason. I have always agreed that the upper a-arm is in a bad orientation and that a longer spindle or taller balljoint improves that situation. My argument has been that a 2" dropped spindle and a taller balljoint is better than a 2" dropped spring and a taller balljoint.


I am having issues with your spindle length pivot to pivot.

Let's watch the terminology so we don't confuse each other ;). "Pivot" is the a-arm shaft center as I defined in the beginning of this thread.

Anyhow, I have a stock tri5 spindle with the two balljoints torn apart to expose the balls. The center to center distance of the balls is 9.75". I can post a pic if needed. I assume a 1/2" taller balljoint makes that 10.25". I don't see where you're getting 11" as the spindle height with the 1/2" taller balljoint. That's a huge discrepancy that needs to be resolved. I hope I didn't "lose" an inch with the tape measure...will check.

[chevynut]

This is a screen shot of my corrected layout using C'nut data points accept I set stock spindle height at 10.5 and lower ball joint .875 down at stock ride height.

Why are you using those dimensions when I already calculated the stock balljoint height is .64" below the pivot and I think we agree that the pivot (dimension A) is 11"? We should stick to agreed-upon dimensions instead of changing them willy-nilly.


The light blue is stock and stock with 1/2 taller ball joint. The minute you put a 1/2 inch taller ball joint on the IC moves to the correct side of car.

Per my measurements, it does not. A 1/2" taller balljoint makes the spindle the same height as the a-arm pivots, 10.25". Therefore with a level lower a-arm the upper a-arm is also level and the instant center is at infinity. In stock position, with the balljoint down .64" the upper a-arm is pointing downward at the balljoint so the instant center is STILL on the wrong side of the car, a long ways out. As the lower balljoint rises, the upper a-arm angle increases and the IC moves to the opposite side of the car, but a long ways out and below the level of the lower a-arm pivot. I believe the roll center could still be below ground but need to verify. In any case I don't see why you'd expect a "dramatic" change.

I think we need to resolve the spindle length before we get into more analysis. I assume you used your 11" spindle length in your layout which I believe is wrong. Let me show you the picture tomorrow. ;) I am going to ignore your layout for now. ;)


I don't believe the assumpton if its on wrong side is really ok from a handling stand point.

I don't think anyone said it was. I have always said that a taller spindle is good.

[chevynut]

This is very good info about alignment something I have always said is very important in this dicussion. Note what it says on top of page 4 about camber setting old train of thought vs today. This also matches what mine is set at listed many times close to C4 or c5 settings give or take. You get increased handling and stability. http://www.valleyofhastings.com/WheelAlignment2.pdf

I'm not seeing why alignment is even part of this discussion or why it's important to suspension GEOMETRY. I think we can all agree that a little negative camber and a lot of positve caster is desirable for better handing and stability but that's an aside since it's adjustable, and geometry is not without changing parts. Most suspensions can be aligned to the same specs of caster, camber, and toe or they can with a change of upper a-arms as in the case of a tri5.

[rockytopper R.I.P 5-13-2017]

My argument is they work together. Go align your C4 to factory trifive specs and see how you like it you want.
I'm not going to argue with really no point doesn't matter anyhow. I also disagree about your statement drop spring is not changing the dynamics look at my layout the pivot points relative to stock or drop srings have moved in relation to the lower ball jiont but the staring point did not change. The motion of the suspension now takes a more negative camber curve. Why I have always stated this mod improves fender tire clearance it does.
My tape is reading 10.5 stock 11 with half inch taller ball joint. I can post a picture of how I'm measuring it if need be. For the record my layout and measurements are based on me setting the lower pivot at 10.62 sense my cars tire measues a 13 inch radius that should equal the 11 inch with taller stock tire? Do you agree the pivot of the lower ball joint is 2 inches above bottom of spindle as I stated?

[Rick_L]

Rocky, I think your 11.875" effective spindle length with the extended ball joint is wrong. I thought it was 10" stock. Cnut posted 9.75" and while that appears short to me I accepted it. My reasoning is that this is a comparison exercise on paper/cad.

Cnut, I don't know what front end weight has to do with this. Ride height is arbitrary for this exercise, we can make it whatever we want. Knowing the numbers with stock springs and weights makes some sense as a starting point. Even in the real world we can make the ride height whatever we want if we go to enough trouble.

Rocky and Cnut, while of course there are effects from changing the camber and caster, starting with zero camber for the diagrams just makes it easier. If we knew enough parameters about tire patch and weight transfer from roll as well as a bunch of other things, we could predict what conditions would produce a loss of lateral traction - but that's way ahead of where we are now.

Last observation. If we are going to discuss the relative merits of stock based vs. C4 suspension, we haven't introduced the biggest factor into the discussion - the fact that the C4 can wear a bigger tire!

[rockytopper R.I.P 5-13-2017]

Rick I'm saying the stock spindle ball to ball center is 10.5. 11.875 was wrong in my initial layout. My current layout uses 11 with extended 1/2 inch ball joint. As for your tire statement I'm running a 10.4 inch wide tire on front. I dought even the C4 can run much wider but I certainly could be wrong. If you look at my comments about the new dynamic path the supension takes it is way different than stock or with drop spindle. It moves away from the fender and not toward it anymore. This is why I have always argued with you about this.
Rocky

[NickP]

I have followed this thread since it began and have found it to be very interesting. Regarding the last injection of variables, tire size, limitations of fitment within the housing size will narrow it down quickly unless modifications to the surrounding structure are done. Also, changing any front suspension system without regards to the rear seems to devalue the overall exercise.

[chevynut]

Nick, feel free to analyze the various rear modifications ;). Clearly changing front suspension parts affects handling greatly so I don't understand your point. I agree the rearend changes also affect handling but in this thread I want to focus on the front end.

[chevynut]

Okay here's the pic of the stock front spindle with the exposed balljoint balls. Can we now agree that the spindle is 9 3/4" tall? I didn't want to leave the center ambiguous and it took me an hour or so to do this!! :)

http://www.trifivechevys.com/attachment.php?attachmentid=5743&stc=1

[NickP]

Nick, feel free to analyze the various rear modifications ;). Clearly changing front suspension parts affects handling greatly so I don't understand your point. I agree the rearend changes also affect handling but in this thread I want to focus on the front end.

I'll just watch from here on out. I doubt that I could add much to the conversation.

[Rick_L]

Cnut, I stand corrected. Thanks for taking the time to measure.

[chevynut]

My argument is they work together. Go align your C4 to factory trifive specs and see how you like it you want.

The point here is ANY of these suspensions can be aligned to any of your caster, camber, and toe specs. So I'm assuming zero initial camber for the analysis, so they can all be compared equally throughout 3" of motion: 1" extension and 2" compression. We're trying to COMPARE suspensions here. No sense in muddying the water by injecting alignment specs. ;)


I also disagree about your statement drop spring is not changing the dynamics look at my layout the pivot points relative to stock or drop srings have moved in relation to the lower ball joint but the staring point did not change.

Of course the starting point changes. The starting point with the dropped spring has the a-arm pointing up at the outboard end and the car is lower. To me "starting point" is the condition the suspension is in at ride height and zero camber. Every one of these mods affects the starting point. From there, we move the suspension through 3" of travel, 1" extension and 2" compression from ride height. That's the way to compare them equally.


The motion of the suspension now takes a more negative camber curve.

That has not been proven yet, imo. That's why we're doing this analysis.


Why I have always stated this mod improves fender tire clearance it does.

With the same lower a-arm length and same camber, I don't see how tire clearance is affected much, if at all. If anything, it's a minute difference as compared to 2" dropped spindles using the same initial camber, since the lower a-arm is a tiny bit shorter.


My tape is reading 10.5 stock 11 with half inch taller ball joint. I can post a picture of how I'm measuring it if need be.

I posted a picture that should clear this up once and for all. I really don't think guessing where the balljoint centers are is the best way to make the measurement.


For the record my layout and measurements are based on me setting the lower pivot at 10.62 sense my cars tire measues a 13 inch radius that should equal the 11 inch with taller stock tire?

IMO what your car measures is not what I'm going to use. I'm going to use the SUSPENSION PARTS you're using, and the same tire size for all modified suspension comparisons. Where your car sits is really not necessary to determine if we have the suspension measurements agreed upon.

I propose that we use a 225/60-15 tire to compare as it's very common on tri5s. I want to measure all of these suspension on the same basis. You added a 1/2" taller balljoint and that makes the spindle 10.25" tall per my measurements. If it's taller, it's not a 1/2" taller balljoint.


Do you agree the pivot of the lower ball joint is 2 inches above bottom of spindle as I stated?

No I don't. I just went and took a better measurement and it's actually 2 13/16 not 3" as I stated before. It's hard to measure accurately with the parallax but I think 2 13/16" is as close as you can get without some specialized measuring equipment and a granite table. This is why we need to agree on dimensions before we do any analysis. I revised the prior post with this new measurement. Glad I haven't done all the analysis yet. ;)

http://www.trifivechevys.com/attachment.php?attachmentid=5744&stc=1

[Rick_L]

Rocky, how do you get a 265 tire under the front of a 55-57 and still have it steer?

[chevynut]

Cnut, I don't know what front end weight has to do with this. Ride height is arbitry for trahis exercise, we can make it whatever we want. Knowing the numbers with stock springs and weights makes some sense as a starting point. Even in the real world we can make the ride height whatever we want if we go to enough trouble.

Rick, what I'm proposing for comparisons is in the list I put together above. I think we have different starting points depending on the ride height at which the suspension is set at zero camber. I proposed 4 ride heights, one with the BJ 1" below the pivot, one with it level, one with it 1" above, and one with it 2" above the pivot. This would equate to different spring lengths or coilover adjustments in the case of the C4 suspensions.


Rocky and Cnut, while of course there are effects from changing the camber and caster, starting with zero camber for the diagrams just makes it easier.

That was the point I was trying to make. We don't need to complicate things with alignment specs. ;)


Last observation. If we are going to discuss the relative merits of stock based vs. C4 suspension, we haven't introduced the biggest factor into the discussion - the fact that the C4 can wear a bigger tire!

I propose we analyze all of the stock tri5 suspensions and modifications (dropped spindles, taller balljoints, dropped springs) with a common 225/50-15 tire. I then propose that we analyze the C4 suspensions with the stock 245/45-17 tire. Most tri5's can't use a 245 tire. I'm not sure what difference tire size really makes except for diameter, which affects ride height and roll center height. Of course in real life a larger tire provides a larger contact patch, but it's center is in the same place with the same wheel offset. Tire size won't make any difference in camber gain analysis.

What wheel offset should we use for the tri5 applications?

[chevynut]

Rocky, how do you get a 265 tire under the front of a 55-57 and still have it steer?

Rick, per his pic his tire is a Kumho 255/45-17. I don't think he gets full steering with it. Not sure where the contact patch is either so if we look at his specific wheels and tires we'll need to know that.

[Rick_L]

Cnut, if we're going to standardize on a wheel to complement a 225/50-17 tire, I suggest a 7" rim with 4.5" backspacing. That's a 0.5" positive offset. This is a wheel/tire that fits "fair" and still has full steering angle. It's one that many use, though some use 4" as it's not a special order for "off the shelf" wheels (that one would be 0 offset). It's going to rub the fender on a lot of cars though. More offset than 0.5" gets you fender clearance at the expense of steering angle, and possible other interference - and you pretty much have to have a "fat lip" billet wheel to be able to even get one with that offset.

For me, I'm not going to change anything or add more stock based ride height configurations, because I think it's getting nit picky. I am going to do C4 next.

As for rocky's tire, I used his 10.4" number to calculate the 265 width.

[chevynut]

I think the best way to lay these out is to locate the lower a-arm pivot and the lower balljoint. Then use the SAI and spindle height to get the upper balljoint location, with zero camber. Then use the upper a-arm length and a-arm spacing to get the upper pivot. You can find the center of the car from the lower a-arm pivot. Then the tire contact patch location and ground level can be determined.

I'm going to summarize all of the relevant dimensions here for clarity:

Stock Tri5 suspension measurements:

Lower a-arm pivot spacing 20.5"
Lower a-arm length 14.75"
Spindle height (balljoint centers) 9.75"
SAI 3.5 degrees
Vertical spacing between upper and lower a-arm shafts, 10.25" (average at center of shaft)
Upper a-arm length 10.25"
Lower balljoint center to spindle center 2.813" (vertically)
Wheel mounting surface to lower balljoint center 4.875"(horizontally)
6.70-15 tire rolling radius 13.36"
Stock wheel offset +0.56"

225/60-15 tire rolling radius 12.40" (BFG)Assumed modified wheel offset +.5" (7" width)
255/45-17 tire rolling radius 12.67" (Kumho)


Early C4 suspension measurements

Lower a-arm pivot spacing 24.125"
Lower a-arm length 13.25"
Spindle height (balljoint centers) 11.875"
SAI 8.744 degrees
Vertical spacing between upper and lower a-arm shafts, 10.84" (average at center of shaft)
Upper a-arm length 8.25"
Lower balljoint center to spindle center 5.625" (vertically)
Wheel mounting surface to lower balljoint center 5.25" (horizontally)
245/45-17 tire rolling radius 12.45"
Stock wheel offset +1.97" (+50mm)


Late C4 suspension measurements

Lower a-arm pivot spacing 24.125"
Lower a-arm length 15.00"
Spindle height (balljoint centers) 13.375"
SAI 18.00 degrees
Vertical spacing between upper and lower a-arm shafts, 11.59" (average at center of shaft)
Upper a-arm length 8.00"
Lower balljoint center to spindle center 5.75" (vertically)
Wheel mounting surface to lower balljoint center 4.00" (horizontally)
245/45-17 tire rolling radius 12.45"
Stock wheel offset +1.97" (+50mm)

Is anything else needed? Do you guys agree with these measurements?

[rockytopper R.I.P 5-13-2017]

Rick I put this wheel on a totally stock 1955 4dr and drove it around doing donuts in my pasture it rubbed nothing car was stock height. That was one of my first ever post that you questioned this. Your inputs and the fame trifive wheel calc drove me to pick a zero offset disc brake. Now that my car is setting on ground lowered with the suspension dialed in to 1 degree negative camber have lots of tire clearance at the fender. My limit is the hellwig swaybar I installed which was apparently designed with disc brakes that move the wheels out. Even the stock 205 tire on steel rim hits it. So I don't get full turn of a stock car. In hine site I probably should have picked the disc that moved it 3/8 or so would have been better. Again with the mod I have the tire is going to move in a totally different arc or direction as stock. For record tire in my pictures is a nitto 555 255/45/R17. 25.95 dia and 10.04 section. I plan to run same tire but a 255/50/r17. It is 27 inches tall and has a 10.4 section stated.

[rockytopper R.I.P 5-13-2017]

Cnut I'm going to agree with your 9.75 spindle stock height. It is apearing like the taller nascar balljoint may be taller than the 1/2 quoted I will report back.
Rocky

[chevynut]

I just re-calculated the position of the lower balljoint on a stock suspension using the 13.36" stock tire rolling radius, the 11" spec at dimension "A" for ride height, and the re-measured 2 13/16" balljoint to spindle height. The lower balljoint is only 0.453" below the pivot at curb weight, so the lower a-arm is nearly level.

[Bihili]

To help the layman (me) understand this discussion here is a picture of stock.
http://i686.photobucket.com/albums/vv226/bihili57/chevysuspension-1.jpg (http://s686.photobucket.com/user/bihili57/media/chevysuspension-1.jpg.html)

[chevynut]

Bill, that's a good visual :) but where did the written dimensions come from? It looks like someone (you?) scaled off of something of known size to get the dimensions. Wish I'd had that drawing a few days ago. ;)

Do I see a SAI of 10 degrees? That's not right per the GM specs. Also, note that the lower BJ is level with the inner pivot. That would probably be the case if there was no flattening of the tire contact patch and you used half the free tire diameter instead of rolling radius along with the specified height from the ground to the lower a-arm pivot to generate the drawing. The average of the 9.76" and 11.16" dimensions. which I assume are the ends of the upper a-arm shaft, is 10.46". I measured that dimension at 10.25". I wonder how accurately that picture is drawn and which dimension is correct. It's not easy to measure that and I'd like to confirm it.

[Rick_L]

What I see in bihili's diagram is a spindle height (bj to bj) of 10", not an SAI of 10 degrees, and not the 9.75" that you clearly measured. And a vertical distance of 9.76" between shaft centers. For that dimension, is it from the bolt head? We're now using the average height, and it's higher.

Also if you hold a straightedge to the drawing, the lower control arm shaft is lower than the ball joint, as is the upper. But we don't know at what ride height, maybe this is at "design load".

While it's good to keep the information coming, I think we may be in pretty good shape on the way things really are/were.

Another example of that is the published track width. If you back calculate from it, you get 59" wheel mounting surface to wheel mounting surface. Yet that measurement on my car is 59.5" and I'll stick by it.

[Rick_L]

I'm certainly not pouring concrete on my diagrams yet, but here's what I have for the C4:

Early C4
Roll center height +1.67"
Roll moment arm 16.60"
I.C. location 116.8" right
Scrub radius 1.14"
Camber gain in 1" wheel travel 0.61 degrees

Late C4
Roll center height +3.31"
Roll moment arm 14.96
I.c. location 58.26 right
Scrub radius -1.18"
Camber gain in 1" wheel travel 1.23 degrees

I used Chevynut's most recent posted numbers. I did the layout by starting with the lower control arm pivot location and length, horizontal lower arm, then spindle length at zero camber using the SAI, then fixed the upper arm by length and vertical pivot height. This is the way I've been doing it all along.

My numbers are not as much departure from stock as Cnut's numbers, and the scrub radius on the late C4 is a lot less, though still negative. The thing that surprised me is how short the "swing arm" length is. My references suggest that a short swing arm promotes "jacking" like you see on a VW bug or early Corvair rear suspension. However with those, the swing arm is much shorter yet.

[rockytopper R.I.P 5-13-2017]

First off Cnut I agree with all your numbers for stock. Using your number it takes a .875 extended ball joint to move the arm angles so the IC and roll center are corrected. My measurements indicate I have at least a .875 taller ball joint it may be 1 inch taller. I have a call into the supplier Mark at sc&c to verify. This below is a quote from the other site discussion effect of taller ball joint. I thank this is pretty accurate info. You guys may continue to analysis in more detail but I'm resting my case. it does not matter the starting point much the angle change beween the arms is the most important thing. it looks like a drop spindle with taller ball joint would have a roll center about 2 inches above drop springs but they want have the same camber curve so I'm going to ask Marks take on why he says springs an not drop spindles. I will report back. I highly doubt we can determine a real camber curve analysis doing 2 d layouts. I would thank a 3d kinematic model would be required. Carry on.
Rocky


Stock tri-5 lower ball joints are positioned stud down. Installing a lower BJ with a longer stud will raise the vehicle ride height & create another issue due to the tri-5 short spindle height. The upper A arm will probably be pinned to the frame bumper. No need to figure the roll center with this configuration it is in the outfield.
When extrapolating suspension pivot points to determine roll center height a stock height 57 has an instantaneous center that does not cross the vehicle center line it intersects at the outside of the vehicle. This suspension design adds positive camber during bump, to the outside wheel during a turn & both wheels during braking.
A vehicle handles better when a loaded wheel changes to negative camber.
Using a stock height 57 with a 28" diameter radial tire which has a squat radius of 13" as an example: Installing a 1" taller ball joint in the upper control arm moves the instantaneous center across the vehicle vertical center line to the correct side of the vehicle. With this modification your front roll center is now 2.75" above ground, the suspension now changes to negative camber during bump, braking etc = a good handling vehicle that will roll a corner rather than plow through it..
Adding taller ball joints will effect camber setting with no effect on caster.
BTW: Upper ball joints experience more load force during hard braking than they get from suspension loading. The spindle acts as a lever through the ball joint trying to twist the upper control arm mount off of the frame.

[Rick_L]

Rocky, there is no "absolute correct" roll center height or amount of camber gain. Like with building engines or many other things, there are many compromises and everything has to work together as a package.

[Rick_L]

I must admit to lack of knowledge on what extended ball joints are on the market.

The Howe upper ball joints that fit our cars are available in 0.1", 0.2", 0.3", 0.4", 0.5", and 0.9" extra length.

Previously I had only seen references to 1" extended ball joints. And the tall spindles that all the pro-touring types are in love with seem to come only in 1" extra length - just like the C3 spindle compared to stock.

Do the circle track racers want to fine tune camber gain in small increments based on different track length and banking? Or do the studs and balls fit other ball joints that might be used for lower ball joints to fine tune bump steer? A quick google search did not enlighten me.

[55 Rescue Dog]

Just throwing this into the mix. There are 2 ends to the car. Nobody ever talks about the rear, which is just as important as the front! Weight distribution, with endless variables, as a package, which mean nothing on paper. You have to drive it to know.

[rockytopper R.I.P 5-13-2017]

Rick I believe your correct about .9 being the max. Thats probably what I have. My cutlass A body is far worse in bump steer stock than a tri five. It has a .9 ext top and .5 ext bottom to correct its issues.

I also think I miss stated about the drop spindle roll center compared to drop springs I thank they are closer than I stated. Because I forgot to move instance center down 2 on drop spindle.

[chevynut]

What I see in bihili's diagram is a spindle height (bj to bj) of 10", not an SAI of 10 degrees,

Yes, that could be correct. It looked like 10 degrees to my eyes but 10" makes sense if you scale it off of some known dimension.


And a vertical distance of 9.76" between shaft centers. For that dimension, is it from the bolt head? We're now using the average height, and it's higher.

Yes I interpret it to be 9.76" at the REAR bolt head but we know the a-arm shaft angles upward from there. I don't see how you get the front one from that drawing. One could get the anti-dive angle and use it to calculate the distance at the center of the shaft.

Also if you hold a straightedge to the drawing, the lower control arm shaft is lower than the ball joint, as is the upper. But we don't know at what ride height, maybe this is at "design load".


While it's good to keep the information coming, I think we may be in pretty good shape on the way things really are/were.

I'm beginning to agree. Getting any closer may just be nitpicking. It's too bad GM doesn't give an exact upper or lower a-arm length somewhere, and we could use it to scale off of that drawing. I did measure a spindle from top to bottom of the casting, and it's 10.5".

[/quote]Another example of that is the published track width. If you back calculate from it, you get 59" wheel mounting surface to wheel mounting surface. Yet that measurement on my car is 59.5" and I'll stick by it.[/QUOTE]

Yes, I have seen that discrepancy too. When I did my layout using the GM specs, the wheel offset was off slightly when I used the published track width and my measured dimensions. So there's a slight discrepancy somewhere, but it probably doesn't matter.

If we can agree on the dimensions I listed, I want to start doing the analysis for all the configurations. Bill's drawing caused me to pause.

[chevynut]

First off Cnut I agree with all your numbers for stock. Using your number it takes a .875 extended ball joint to move the arm angles so the IC and roll center are corrected. My measurements indicate I have at least a .875 taller ball joint it may be 1 inch taller. I have a call into the supplier Mark at sc&c to verify.

Not sure which of your measurements you're talking about. The spindle is 9.75" with the stock balljoints, which I think I proved, and your balljoint is 1/2" taller than stock as advertised, then your spindle is 10.25" tall. And the a-arms are parallel when the lower one is level. If the balljoint is actually longer, then it's a different story. Maybe you can get a drawing for the actual balljoint somewhere. Do you know the Howe part number? If it's taller, it's a good thing. ;)


This below is a quote from the other site discussion effect of taller ball joint.

I've read a lot of stuff from "churchkey" and he seems to understand a lot, but I've read some that was BS. What he said in that post is nothing new...it's what we've been saying all along. We're just trying to understand the full effect of that taller balljoint, and what it REALLY does to camber gain and roll center. Until I do an analysis using a 1" taller balljoint (which may not exist) to verify it, I don't believe his numbers. And he didn't even quantify the camber gain. Plus, there is no mention about cut springs versus dropped spindles, which is what a lot of this debate is about.


You guys may continue to analysis in more detail but I'm resting my case.

Just what is your case? That an extended balljoint helps? We knew that long ago. But you haven't proven one thing that shows a 2" cut spring is better than a 2" dropped spindle.


it does not matter the starting point much the angle change beween the arms is the most important thing.

The starting point (where the lower balljoint is in relation to the pivot) affects the angle between the a-arms. Why don't you see that? If it didn't, you wouldn't have any camber gain.


it looks like a drop spindle with taller ball joint would have a roll center about 2 inches above drop springs but they want have the same camber curve

Where do you get to that conclusion? What are your assumptions? Show your numbers if you've done the analysis. I'm going to do mine anyhow. ;)


so I'm going to ask Marks take on why he says springs an not drop spindles. I will report back.

I would like to hear what he has to say. And I want to see proof of his conclusions not just opinions.


I highly doubt we can determine a real camber curve analysis doing 2 d layouts. I would thank a 3d kinematic model would be required. Carry on.
Rocky

This can easily be made into a 2D problem by looking at the suspension at the centerline of the axles like we're doing. There's no reason for a 3D model. I don't think any suspension software I've seen uses 3D models. Caster causes the hubs to move back but the overall effect is negligible imo. You could correct for it in the 2D model by calculating the exact position of the upper a-arm due to caster angle. All we're looking for is COMPARISONS in the suspensions, not absolute values.

[chevynut]

Just throwing this into the mix. There are 2 ends to the car. Nobody ever talks about the rear, which is just as important as the front! Weight distribution, with endless variables, as a package, which mean nothing on paper. You have to drive it to know.

Sure, just like all engineers drive the car before they design the suspensions, right? LOL! Of course the rear roll center matters in the whole scheme of things, as does camber gain with an IRS which will outperform a solid axle. But this debate is about the effect of a taller balljoint and other mods to the FRONT of the car. If you want to analyze the rear suspensions, and look at all those "endless variables", start your own thread. Otherwise, please stay on topic. ;)

[chevynut]

Rick I believe your correct about .9 being the max. Thats probably what I have.

Here's a link to the Howe site. What is your upper balljoint part number?

http://howeracing.com/p-7929-howe-22304-fits-k6034.aspx




Change


0"


+.1"


+.2"


+.3"


+.4"


+.5"


+.9"




Part No.


22380


22381


22382


22383


22384


22385


22389A




Dim. X


1.186"


1.286"


1.386"


1.486"


1.586"


1.686"


2.086"




Dim. L


3.15"


3.25"


3.35"


3.45"


3.55"


3.65"


4.05"





22381 +.1"
22382 +.2"
22383 +.3"
22384 +.4"
22385 +.5"
22389 +.9"


http://static.speedwaymotors.com/RS/SR/Alternative/50/917223375%7E1_L_18edb367.jpg

[55 Rescue Dog]

Sure, just like all engineers drive the car before they design the suspensions, right? LOL! Of course the rear roll center matters in the whole scheme of things, as does camber gain with an IRS which will outperform a solid axle. But this debate is about the effect of a taller balljoint and other mods to the FRONT of the car. If you want to analyze the rear suspensions, and look at all those "endless variables", start your own thread. Otherwise, please stay on topic. ;)
Sorry again, but I do believe that AFTER the engineers design a front suspension they drive it at a place, I think, called GM proving grounds, before the design is approved, and released into production, and sold to the public.

[markm]

Sorry again, but I do believe that AFTER the engineers design a front suspension they drive it at a place, I think, called GM proving grounds, before the design is approved, and released into production, and sold to the public.

I believe that was part of the plan for the race track at Indy when built.

[rockytopper R.I.P 5-13-2017]

Here's a link to the Howe site. What is your upper balljoint part number?

http://howeracing.com/p-7929-howe-22304-fits-k6034.aspx




Change


0"


+.1"


+.2"


+.3"


+.4"


+.5"


+.9"




Part No.


22380


22381


22382


22383


22384


22385


22389A




Dim. X


1.186"


1.286"


1.386"


1.486"


1.586"


1.686"


2.086"




Dim. L


3.15"


3.25"


3.35"


3.45"


3.55"


3.65"


4.05"





22381 +.1"
22382 +.2"
22383 +.3"
22384 +.4"
22385 +.5"
22389 +.9"


http://static.speedwaymotors.com/RS/SR/Alternative/50/917223375%7E1_L_18edb367.jpg

Laz I have no part number but my measurements equal the .9 exactly. I thank i have been saying 1/2 inch all along which probably caused alot of disagreement about this using that does not correct the problem so I will eat ever word I ever said and agree with you and Rick. However using a .9 taller ball joint does correct the problem. Sense I had never ever done the numbers but knew it worked because you can still deny all you want but my daily driven cutlass is a good comparsion as to how much improvement is realized with this. For the record I have already done the analysis to back up the number. You may input the .9 ext ball joint in your model and publish the numbers I will agree with them. I'm resting my case because what I have really said all along or was trying to is this corrects the IC and Roll center location. I still believe having it on the wrong side is not good and I still dont think the roll centers you are using in that case are correct. I have found no information to support that other than you and Rick. If there is good info to support the case of having ic on wrong side please share it. I also agree the rear comes into play in the big picture as to tires alignments spring rates shocks etc etc but thats not what we are duscussing here. Im sure the C4 will have an edge in racing performance over the bolt on solution but want be night and day. So if your building a cruiser most folks will be happy with the bolt on fix. We've shown both bolt on and C4 are close in price or can be. C4 does have curb appeal so both are Good. If I get more info from Mark I will share.
Rocky

[Mike56]

I'm following this thread and i'm learning from it. Some of this is beyond me know but it's soaking in as you go. I'm looking forward to your conclusions( table/chart) on the affects of different suspension part changes. I hope to apply that to improve the handling of my car. I'm also enjoying the differing opinions as they tend to bring out more information, drawings, and resources. Keep up the good work.

[rockytopper R.I.P 5-13-2017]

I'll include this photo sense Rick brought in tire size. This is my current steering limit. Hope its enough lol. The wheel shown is a 17x8 zero offset tire is a nitto 555 with 25.95 dia and 10.4 section. The other side of the car has a stock steel rim and 205 tire. It is hitting the helwig sway bar in this photo. I do not have rotters on they will move wheels out .25 eash side. So I call this my limit and will build and set steering stops here.
http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_167.jpg

[chevynut]

I have no part number but my measurements equal the .9 exactly. I thank i have been saying 1/2 inch all along which probably caused alot of disagreement about this using that does not correct the problem so I will eat ever word I ever said and agree with you and Rick.

Thanks for verifying that. A .9" taller balljoint will have more effect than a .5" taller one, obviously. That's why I kept asking you why you didn't go with the longer one. ;) I'll add that to my model and work on it with a 10.65" tall spindle.


However using a .9 taller ball joint does correct the problem.

It does put the upper balljoint above the pivot thus moving the instant center to the opposite side of the car. It also improves the camber curve, but I'm not sure by how much at this point. I was waiting for you to verify the balljoint length before I went any further with the analysis. I think we should forget the 1/2" taller balljoint and analyze the .9" taller one. We still have a disagreement about the effect of dropped spindles versus 2" dropped springs and I hope the analysis clears that up too.


Sense I had never ever done the numbers but knew it worked because you can still deny all you want but my daily driven cutlass is a good comparsion as to how much improvement is realized with this.

You keep saying I deny it :geek:. I have never, EVER said that a taller spindle is a bad thing. I have only objected to your claim that angling the lower a-arm up using 2" cut springs is better than "junk" 2" dropped spindles. As I've said many times the 2" dropped spindles drop the CG without negatively affecting the suspension attitude.


I'm resting my case because what I have really said all along or was trying to is this corrects the IC and Roll center location.

But it's clear that angling the lower a-arm up at the balljoint by cutting the springs moves the roll center DOWN, and AWAY from the CG isn't it? I don't even have to do an analysis to see that. The IC moves downward and so the roll center drops. As the spindle length increases, the IC gets closer to the car and rises, improving the roll center. And don't forget, you ALSO said the 2" cut springs are better than the 2" dropped spindles. That is my main objection to your claims as I've said many times before.


I still believe having it on the wrong side is not good

Nobody has said it was a good thing. Why do you keep harping on that? ;) Go back and read my comments on all the other threads about this issue.


I still dont think the roll centers you are using in that case are correct.

Not sure what you're getting at with that comment. I have completed the analysis of the stock suspension and the roll center is below ground up to 2" of compression. Once you get to where the balljoint is about 2" above the pivot the IC actually "flips" to the other side of the car but it's a long ways away and way below ground so the roll center is still below ground.


If there is good info to support the case of having ic on wrong side please share it.

There isn't any. It's a bad configuration and I don't think anyone has EVER said otherwise. Please don't say that again. :) :) :)


Im sure the C4 will have an edge in racing performance over the bolt on solution but want be night and day.

I think the difference will be dramatic. Also, when you consider all the other factors as you mentioned, like anti-dive, SAI, camber gain, scrub radius, the IRS roll center, and many other factors it's a completely different suspension system, FAR better than any stock or modified stock setup. That's why the guy on the other forum said the C4 car he drove was better than any Tri5 he's ever driven. :)


So if your building a cruiser most folks will be happy with the bolt on fix. We've shown both bolt on and C4 are close in price or can be.

That's not what you've been claiming though ;) :). I've read where you said here and elsewhere that your car drives like a C4 Vette, and you get the same suspension geometry at a lot less cost with a simple fix. When you first introduced the idea here you said you got the same "alignment" as the C4. As I've said, static alignment is a tiny part of the overall suspension picture. And yes, the C4 setup is cost competitive with all the bolt-on mods if you go all-out. Your extended balljoint addresses one aspect of the poor stock suspension design, but not all of them. If you get a chance, drive a tri5 with the C4 setup and tell us what you think. There's quite a few of them around.

[rockytopper R.I.P 5-13-2017]

I left the protouring community when I bought my nomad and joined this one. I learned from the PT community who live and breath making older cars handle better. Very few use drop spindles drop springs are preferred for the reasons I have stated. One main issue with drop spindle is it limits tire size amoung other things and the drop spring improves the camber because it uses the right part of the curve. I didn't make this up. Good reading here and from some of the best in the business.
Rocky

http://www.pro-touring.com/threads/209-Drop-spindles-vs-drop-coils-(from-old-site)

[Rick_L]

Yesterday while I was googling extended ball joints, I visited the SC&C website (rocky's guru). I also read a couple of posts by him on chevelles.com and another forum.

Turns out he sells dropped spindles, tall ones, and extended ball joints, all 3. He even sells a spindle that is dropped AND tall, I think for early Camaros.

What's up with that rocky?

[chevynut]

One main issue with drop spindle is it limits tire size amoung other things and the drop spring improves the camber because it uses the right part of the curve.


Rocky, how does a dropped spindle limit tire size? I guess I'm not familiar with that issue. And what are the "other things" you talk about that makes you call them "junk"?

Also, a lower a-arm that's pointing up at the outboard end at ride height is just plain wrong imo. As I said, it causes more tire scrub as well as negating part of the camber gain from the extended upper balljoint because the balljoint is moving inboard at a faster rate there. I hope my analysis convinces you of that, or changes my mind on the matter. ;)

Are we discussing a car set up for pure racing, or one that's pro-touring?

[chevynut]

Good reading here and from some of the best in the business.
Rocky

http://www.pro-touring.com/threads/209-Drop-spindles-vs-drop-coils-(from-old-site)

And none of this from your link applies to a Tri5 as far as I know...it's all about 1st gen Camaros:

"The drop spindle kits use second gen parts, on a cast iron spindle similar to a second gen spindle with caliper mount cast in. The steering arm is two inches lower than a stock Camaro and the caliper mounts two inches higher in relation to the upper A frame, which can cause caliper to A frame clearance problems.

Several problems develop when you use drop spindles.

You can't fit wide tires, the tie rod end winds up two inches lower in relation to the wheel, so forget wide front rims.

Geometry stays stock which is not good on a Camaro.

You may have clearance problems with the upper ball joint to caliper.

You can't use any aftermarket disc upgrades, they won't fit.

Steering arms are cast in, so you can't bend them to fix bumpsteer. You would have to use a rod end and spacers on a stud.

Just installing shorter coils puts the stock spindles on a better part of the camber curve, which is an improvement all by itself. The lower A arm will not be level, which is not ideal but it isn't that bad.
David "

So what he's saying is you ideally DO WANT a level lower a-arm. In that case you need to lower the CG of the car some other way...like dropped spindles. You need to fix the upper a-arm orientation with a taller spindle. His comment about getting to the "right part of the curve" is getting the upper a-arm in a better position. That can be done with a taller balljoint. And he didn't even address the roll center dropping with the lower a-arm level, but implies that a higher roll center is good.

I'm not aware of any wheel clearance problems on a tri5 and the steering arm is removable.

THAT is why a dropped spindle is better than a dropped spring on a Tri5. ;) He confirmed it for me. ;)

[rockytopper R.I.P 5-13-2017]

Yesterday while I was googling extended ball joints, I visited the SC&C website (rocky's guru). I also read a couple of posts by him on chevelles.com and another forum.

Turns out he sells dropped spindles, tall ones, and extended ball joints, all 3. He even sells a spindle that is dropped AND tall, I think for early Camaros.

What's up with that rocky?


He sure does Rick infact he sales drop setup from chassis works for trifive very pricey hardware more than cnuts rolling package. Its the frist thing he promotes on his sight. How about call mark some time and discuss this with him. Ive always agreed threre are drop spindles out there with corrected arms top and bottom probably engineered by several companies but bottom line the price point is why I advocate this cheaper compromising mod as you guys state and why mark does to if your on the low end of a budget. And he will tell you your gonna be very happy with the performance of this very affordable add on. And for record and again because of your previous inputs about tire clearance before I decided to go with marks setup again i was considering ride tech and even cnuts product. I saw that drop spindle brakes pulled tires inbd so I directly ask mark when dicussing my nomad package if I should use drop spindles and he said no stick with the stock. I cannot qualify why he said not to use drop spindles but if you wish to know you can call him. I have a call in as aready said and will report back if he responds to request. I'm pretty sure its becaused of the improved camber gain may out weights the roll centerloss.

[Rick_L]

Rocky I don't know how to say this without seeming rude - but you've been changing your story a lot. Especially your dropped spindle story. They used to be junk, now they are just expensive. I think in the big picture they aren't expensive. Chevynut has yet to comment on the C4 numbers I posted yesterday, but they aren't THAT much better than the extended ball joint. And extended ball joints with dropped spindles seems better yet.

I also wonder how you're going to maneuver that car, especially parking, with the limited steering angle you have. Maybe even the goodguys' autocross.

[rockytopper R.I.P 5-13-2017]

I appolize Rick I thought your saying the IC being on wrong side isn't a big deal it kinda of confuses with your statements now?
Rocky


When the i.c. location changes from outboard to inboard, this is not as big a deal as you might first think because all it means is that the lateral location of the intersection has moved from one side of infinity to the other. In other words it's going from increasingly longer to decreasingly longer. It doesn't signify an abrupt change in actual handling as you might first think. What does cause abrupt changes in handling is an abrupt change in the height of the i.c. and consequently the height of the roll center.

The main contributor I can think of that will cause the i.c. and roll center to change vertically more rapidly is shorter control arms. Thing is, shorter control arms also give you more camber gain. So you have to balance those two things.

One way to control all this movement of roll centers and negate the need for camber gain is simply to make the suspension stiffer and set a bunch of static camber. Of course that's a problem with ride and with road surfaces that are rough as well as tire wear. So everything is a compromise - "more is better" isn't nearly the option that it is with other things.

I wouldn't pay nearly as much attention to the location of the instant center as to the location of the roll center, or the movement of the i.c. and the roll center.

One thing we haven't discussed much is the roll couple and the length of the moment arm which is the distance between the center of gravity and the roll center. The roll couple, which is the unsprung weight multiplied by the moment arm, will partially determine how the car rolls over when cornering, so while the roll center at ride height is important, how much the roll center and moment arm changes with suspension travel is also important.

which answers this question the link also disagrees about defining roll center per your definitions also why I questioned it.


This has some very good info about subject. So Rick I'm still confused about the instant being outbd or on wrong side. This discussed the 2 an states complex F1 cars have instant on wrong side and so quickly diposes it in futher topic and carries on with the normal ic on opposite side?
http://www.motoiq.com/MagazineArticles/ID/2804/The-Ultimate-Guide-to-Suspension-and-Handling-Its-All-in-the-Geometry-Part-One-The-Roll-Center.aspx

[rockytopper R.I.P 5-13-2017]

Rick your right about limited steering handy capping autocross my cutlass has same issue better suited for road course. I did blame you and cnut wheel calc for that above looks like i should have used a disk that pushed out further. The bar was probably designed when the common wide space disc kits that were norm were in use until more options came on board. Like i said the stock tire hits it. This is a shot with the boss on board in a go cart turn the one you see the car go into a 4 wheel drift in previous video I posted. The black 55 is running drop spindles he is running 3 seconds behind me a little less than my time behind the pros. Turns out he works at same place, he is switching to the setup I have. Will be able to post results on real trifive soon. So I'm still waiting on mark before I poor concrete. Would like to continue how to make a car handle discussion but they are all junk when you head to the rookies and play in the snow were the boss is taking me for our anv.
I'll analysis the camber curve on our z71 see if it needs spirings or spindles lol. Ill catch back up on sports cars when we return to the flat lands lol.

http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_168.jpg

[chevynut]

Okay guys I've finished my analysis :), and checked and re-checked the numbers. I was having some kind of problem with my CAD software and some of my files, so I had to unistall it and re-load it.

I looked at each configuration at ride height (assume lower a-arm level except for 2" cut spring) and with the balljoint 1" below, 1" above, and 2" above level. The roll center range below is the amount the roll center moves with suspension movement. I understand it's better is it doesn't move much.

I have to say I'm actually pretty impressed with what the 0.9" tall balljoint does. My initial thoughts were that the 1/2" taller balljoint didn't make that much difference and I still don't think it does although it's a step in the right direction. That's been my main argument as well as the dropped spindle versus dropped spring issue. But the 0.9" balljoint fixes a big issue with the stock front suspension.

The two issues I see with the tall balljoint and cut spring combination is the length of the roll moment arm, and increased tire scrub. I'm impressed with how roll center doesn't move as much as ny other stock suspension configuration, though it is below ground. The camber gain almost exactly matches the early C4 suspension, which surprised me ;). The roll moment arm is about the same as a stock suspension with dropped spindles, but over 2" longer than the same with the extended balljoint. The issue to me is the .22" net tire scrub. If you're racing, this probably isn't a big deal. But I think it would tend to wear tires more on the street.

Comparing the 2" dropped spindles and tall balljoint to the 2" cut springs and tall balljoint, there are tradeoffs. The dropped spindles have a 2" shorter roll moment, but the roll center moves more. There is less camber gain, but also a lot less tire scrub...almost none at 0.039".

But the late C4 is better in just about every parameter than all of the rest. It has a much shorter roll center moment arm (~5.5" shorter than the cut spring and tall balljoint), more camber gain, and very little tire scrub at -0.070". The best tire scrub was the early C4 at only -0.027"

I have a spreadsheet full of numbers but I'll try to summarize it. I only looked at roll centers, roll center range (stability), roll moment, camber gain, and tire scrub (not scrub radius). Tire scrub is from the combination of camber change and lower balljoint lateral movement.

Here's my results...it's actually easier to look at it in the spreadsheet. :eek:

Roll center and roll center range and RC moment arm at ride height

Stock with stock 6.70-15 tire - roll center -1.76"; RC range 2.98"; roll moment 22.76"
Stock with 225-60-15 tire - roll center -1.50"; RC range 3.33"; roll moment 21.54"
Stock with 2" dropped spindles 225 tire - roll center -1.19"; RC range 3.90" (flips sides); roll moment 19.23"
Stock with 0.9" extended balljoint and 225 tire - roll center +.96"; RC range 3.57"; roll moment 19.08"
Stock with 0.9" extended balljoint, dropped spindles and 225 tire - roll center +.76"; RC range 4.05"; roll moment 17.28"
Stock with 2" cut springs, 0.9" extended balljoint, 225 tire - roll center -1.30"; RC range 2.92"; roll moment 19.34"
Early C4 (in tri5 frame) - roll center +3.15"; RC range 2.07"; roll moment 13.85"
Late C4 (in tri5 frame) - roll center +3.79"; RC range 1.02"; roll moment 13.21"


Camber

Stock @1" bump +0.21 degrees
Stock @2" bump +0.24 degrees

(stock with dropped spindles same as above)

Stock with 0.9" extended balljoint @1" bump -0.28 degrees
Stock with 0.9" extended balljoint @2" bump -0.73 degrees

(Stock with dropped spindles and extended balljoint same as above)

Stock with 0.9" extended balljoint & cut springs @1" bump -0.64 degrees
Stock with 0.9" extended balljoint & cut springs @2" bump -1.49 degrees

Early C4 @1" bump -0.64 degrees
Early C4 @2" bump -1.50 degrees

Late C4 @1" bump -0.73 degrees
Late C4 @2" bump -1.68 degrees

Tire scrub (inboard positive)

Stock with stock tire - +.180"
Stock with 225-60-15 tire - +.176"
Stock with 2" dropped spindles 225 tire - +.168"
Stock with 0.9" extended balljoint and 225 tire - +.014"
Stock with 0.9" extended balljoint, dropped spindles and 225 tire - +.039"
Stock with 2" cut springs, 0.9" extended balljoint, 225 tire - +.220"
Early C4 (in tri5 frame) - -.027"
Late C4 (in tri5 frame) - -.070"

Thoughts? I'm not sure how these numbers compare to what you guys got. Maybe I should scan and post the spreadsheet. ;)

[chevynut]

The black 55 is running drop spindles he is running 3 seconds behind me a little less than my time behind the pros. Turns out he works at same place, he is switching to the setup I have.

Not sure that really means anything. So you're comparing a Cutlass to a tri5 and concluding the 3 second difference is due to the dropped spindles? What about the driver, tires, engine, tranny, and all those other things you guys keep mentioning?

It would be valid if you took the same car and the same driver on the same course on the same day and swapped out just the suspension parts.

Besides, you'd all be better off with a late C4 suspension, per my analysis. ;)

[Rick_L]

Chevynut, our numbers don't agree in detail, but the general trends do agree with exception of a couple of instances. It's easy to make a seemingly minor mistake and get off course. I will go back and review the cases in more detail later and make some comments/questions. I do know that as some of the numbers were updated I didn't go back and revise them for the stock suspension cases (two I can think of are tire rolling radius and the amount of ball joint extension (I used 1" not 0.9"). The biggest discrepancy in our numbers is the early C4. I'll go back and triple check mine.

Rocky, my Hellwig swaybar interfered with turning too. My C3 brakes have front mount calipers, and the calipers hit. I heated and bent the bar a little bit and fixed it.

While we're on the subject of swaybars and 55-57 suspension, the engineer at Hellwig videoed and timed a 56 on an autocross course. I don't remember whether the initial run was without one or with a small bar. The end configuration was their big bar. A dramatic improvement, definitely more than 3 car lengths difference in the result. So just that can make that difference. The videos are in a post on trifive.com. His name over there is "Dave @ Hellwig" or something close to that.

[chevynut]

If you decrease the roll center moment arm length you don't need as big of a swaybar. ;)

I knew our numbers were off a little, that's why I did mine so many times.

To review, this his how I did it.....I started with the inner lower pivot as the 0,0 datum and located the lower balljoint. Then I made a line from the lower balljoint at the SAI angle and intersected it with a circle from the lower balljoint whose radius was the height of the spindle. That located the upper balljoint. From there I used the inner pivot height (horizontal line) and a circle the length of the upper a-arm to locate the upper pivot at their intersection. I located points 1" and 2" above the lower balljoint on the arc of the lower a-arm. From each of those points I made a circle with a radius the same as the spindle length, and intersected a circle that represented the upper a-arm arc to get the corresponding upper balljoint locations. The centers of each of those balljoint locations gave me the change in SAI, which is the same as camber change.

[Rick_L]

I did what you did except to make a new layout at a new ride height, I simply moved the control arm shafts up or down in the increment selected. Then I drew new arcs for each control arm. Doing both control arms that way accounts for a slight lateral change in the lower ball joint location.

To review, I establish the lower control arm pivot location. Swing an arc for the lower control arm length. The lower ball joint height is fixed - so where the arc intersects that height is the lower ball joint location. For the initial case, the upper ball joint location is determined by spindle length 0 degrees camber and SAI - then the upper pivot location is determined from its height and the control arm length. For compressed or extended suspension (or other ride heights), I swing an arc for the spindle height, and an arc for the upper control arm length. The intersection is the upper ball joint location.

[chevynut]

I think we're doing it the same way, actually. I used zero camber for the initial cases (starting point) too. I only calculated 2" bump from level, not 1" extension to 2" bump so maybe that's the difference in our numbers.

[Rick_L]

I did some extension layouts early on, but didn't later, and I never reported any results from that. If you base your camber gain as degrees per inch of wheel travel, and you are doing ride height and 2" compressed, you are dividing the 2" compression camber by 2 to get camber gain per inch - correct?

Thing is, the camber gain isn't linear, so calculating at ride height and 1" compression will give you a different result than above.

Edit: looking back at your results post, you did post camber in 1" increments, I confused now.

I went back and looked at my early C4 layout because that one was the most different from yours. I found an error in the location of the tire patch, but it didn't really make much difference. I get a roll center height of 1.79" vs. your 3"+, and a scrub radius of 2.39" in my corrected layout. Surprisingly, I get 0.63* camber gain in 1" compression vs. your 0.64*. I say surprisingly because the other numbers are so different.

I also went back and looked at the dropped spindle plus 0.9" extended ball joint, which was somewhat of a change in parameters . I had originally used a different tire height and 1" bj extension, but frankly it didn't change my results much, and they are quite close to yours.

I assume that "roll center range" is roll center at different heights. Is that over 2" compression or some other distance?

[chevynut]

Sorry I wasn't more clear. :geek:

The roll center range is the total range the roll center moves vertically over a 3" range of travel i.e. with the balljoint 1" below level up to 2" above level....or in the case of the cut spring from 1" above level to 4" above level. It's the minimum to maximum roll center height. I'm not even sure there's enough travel in the stock suspension for the latter but I calculated it anyhow. That's another deficiency of the cut springs.

The camber is in 1" increments starting from level. I showed camber change from level to 1" above, and from level to 2" above. So they're reported as total change from level. I could easily get the 1" below level camber change but I'm not sure it's relevant.

[Bihili]

While we're on the subject of swaybars and 55-57 suspension, the engineer at Hellwig videoed and timed a 56 on an autocross course. I don't remember whether the initial run was without one or with a small bar. The end configuration was their big bar. A dramatic improvement, definitely more than 3 car lengths difference in the result. So just that can make that difference. The videos are in a post on trifive.com. His name over there is "Dave @ Hellwig" or something close to that.

https://www.youtube.com/watch?v=Yez1J68nN60

Watch the difference in time

[chevynut]

https://www.youtube.com/watch?v=Yez1J68nN60

Watch the difference in time

Interesting that in the run without the swaybars the car actually crossed the last cone ahead of the one with the swaybars, even though the one with the swaybars started the first turn slightly ahead. Does that mean it did the slalom quicker? ;) :)

Was there a timer shown? I didn't see it.

We all know that swaybars work and they're used on virtually every production car out there. No surprises there.

I put a solid 30mm (1 3/16") C4 Z51 swaybar on the front of my Nomad and a custom solid 1" swaybar in the rear with shorter arms than stock C4. I'm hoping they're not too stiff. :eek:

[chevynut]

So from all of this analysis I've concluded a few things...

* The stock suspension sucks. The car rolls a lot with the high CG and long RC arm. Camber goes positive through the first 2" of compression but tire scrub is small.

* The stock suspension with dropped spindles and 225 tires doesn't suck quite as bad ;). The roll center arm length decreases 3" so it should roll less. But the camber still goes positive through the first 2" of compression.

* The stock suspension with dropped spindles AND taller balljoint is pretty good. The roll center arm length decreases almost another 2" and camber is improved a lot. The roll center moves the most of all the configurations, but I'm not sure what that really does. Camber goes negative immediately on compression and is .73 degrees at 2" compression. Tire scrub is almost non-existent and suspension travel is not compromised.

* The stock suspension with 2" dropped springs and taller balljoint improves some things and hurts others. The roll center arm is 2" longer than with the dropped spindles and is more stable. Camber gain is improved...doubled from the 2" dropped spindles/tall BJ. But tire scrub goes to almost 1/4" at 2" of compression travel. Also, suspension travel is limited. The stock tri5 specs say suspension travel is 3.5" in bump at 2/3 a-arm bumper compression. If you start at 2" you only have 1.5" of travel left. You might be able to cut the bumper down to get 2" of travel, but I'm not sure. It would make the bump stop a lot harder.

* The early C4 suspension (in a tri5 set up with 3" drop) is pretty good. Roll center arm length is about 5.5" shorter than the cut spring and long balljoint case and it moves less than any of the stock configurations. Camber gain is about the same, but tire scrub is much less, almost non-existent.

* The late C4 suspension (in a tri5 set up with 3" drop) is clearly the best ;). Roll center arm length is slightly shorter than the early C4 and the roll center moves half of the early C4. Camber gain is 12% higher than the early C4 and cut springs at 2" compression, and tire scrub is still small, though a bit worse than the early C4.

I conclude that Rocky is partly right ;). The 0.9" taller balljoint is a good move in any case. I'm not convinced the 1/2" taller balljoint is worth it but i should help a little. The 2" cut springs and 0.9" taller balljoint will certainly help in an autocross situation AS LONG as you use a stiff rollbar and/or stiff springs, and don't care about tire scrub. For the street I think it's inferior to the dropped spindles and tall balljoint, which is the case I've been making. The dropped spindles and tall balljoint still have good camber gain, a better roll center, and virtually no tire scrub.

However, all that said, the C4 suspensions are still the clear winner, which doesn't surprise me. They're 30-40 years newer!! And they're a lot lighter and cooler-looking than the stock parts. :) :) :)

[chevynut]

I thought I'd go ahead and move this further forward, and look at the C5/6 suspension. I happen to have one here so I took some quick measurements, but can check for accuracy if I get more info.

The upper a-arm is 8 1/2" long.
The lower a-arm is 16" long.
The spindle is 12 1/2" tall.
SAI 8.8 degrees (at zero camber)

The SAI is what I found online from a couple of sources. Some guys say their car is 9.2-9.4 degrees, but that's from an alignment shop so it includes camber.

The dimension I'm missing is the upper to lower pivot points, vertically. Does anyone have this dimension?

http://www.locostusa.com/forums/download/file.php?id=9766&t=1&sid=a04d77ed85f4326100e345a4527f5cfe

[Rick_L]

On the swaybar before/after video, per Dave at Hellwig,

"The side by side was sped up in spots to show the vehicle at the same point in the slalom for comparison. The other veiws are shown in real time. Cones were on a 40 ft spacing which is quite tight due to available area. This kept speeds down but the addition of sway bars increased the speed 7 mph and the car held a tighter line as shown."

I'd say this equates to 2 seconds or way more than 3 car lengths.

[Rick_L]

However, all that said, the C4 suspensions are still the clear winner, which doesn't surprise me.

Of course it will be for you. And some others.

On the other hand, significant improvements have been demonstrated for stock suspensions. The right combination of lowering, taller effective spindle height, sway bars, shocks, and tires goes a long way to making the original suspension better than it started with less trouble.

How much compression travel and total travel is in the early and late C4 suspensions? Seems like the short upper bar esp. on the late C4 is going to cause diminishing returns once it's past 2" of bump. But then maybe they don't bump that far in practice because of the stiff springs and bars. Which one could argue might be as much of the performance as the geometry.

Has anyone like Newman done any autocross demos of C4 vs. stock based?

[55 Rescue Dog]

It pretty much all goes out the window, if the weight distribution is overly front heavy, as for as cornering speeds go. The C4 had a lot of engine setback, compared to the tri five.

[chevynut]

Of course the C4 has a few drawbacks, one of which is the wider WMS width. But it's not that bad unless you want to use zero offset wheels. About 50mm is the requirement for late suspensions and about 36mm for the early ones to stay under the 67.5" wheel width.

Yes as I said there are some improvements that can be made to the stock suspension with bolt-on parts. I personally wouldn't do the 2" dropped spring unless the car was only a racer but the tall balljoint is a big improvement. I think there may be some issue with wheel fitment in some applications.

Here's a bunch of autocross videos from Newman. It's pretty hard to compare the same car with and without the C4 conversion, though, and I don't know of anyone who's done that. Kyle Newman's autocross performance where he beat lots of muscle cars shows how good it it, imo.

http://www.newmancarcreations.com/driving-fun/auto-cross.php

[hutchenc]

So from all of this analysis I've concluded a few things...

* The stock suspension sucks. The car rolls a lot with the high CG and long RC arm. Camber goes positive through the first 2" of compression but tire scrub is small.

* The stock suspension with dropped spindles and 225 tires doesn't suck quite as bad ;). The roll center arm length decreases 3" so it should roll less. But the camber still goes positive through the first 2" of compression.

* The stock suspension with dropped spindles AND taller balljoint is pretty good. The roll center arm length decreases almost another 2" and camber is improved a lot. The roll center moves the most of all the configurations, but I'm not sure what that really does. Camber goes negative immediately on compression and is .73 degrees at 2" compression. Tire scrub is almost non-existent and suspension travel is not compromised.

* The stock suspension with 2" dropped springs and taller balljoint improves some things and hurts others. The roll center arm is 2" longer than with the dropped spindles and is more stable. Camber gain is improved...doubled from the 2" dropped spindles/tall BJ. But tire scrub goes to almost 1/4" at 2" of compression travel. Also, suspension travel is limited. The stock tri5 specs say suspension travel is 3.5" in bump at 2/3 a-arm bumper compression. If you start at 2" you only have 1.5" of travel left. You might be able to cut the bumper down to get 2" of travel, but I'm not sure. It would make the bump stop a lot harder.

* The early C4 suspension (in a tri5 set up with 3" drop) is pretty good. Roll center arm length is about 5.5" shorter than the cut spring and long balljoint case and it moves less than any of the stock configurations. Camber gain is about the same, but tire scrub is much less, almost non-existent.

* The late C4 suspension (in a tri5 set up with 3" drop) is clearly the best ;). Roll center arm length is slightly shorter than the early C4 and the roll center moves half of the early C4. Camber gain is 12% higher than the early C4 and cut springs at 2" compression, and tire scrub is still small, though a bit worse than the early C4.

I conclude that Rocky is partly right ;). The 0.9" taller balljoint is a good move in any case. I'm not convinced the 1/2" taller balljoint is worth it but i should help a little. The 2" cut springs and 0.9" taller balljoint will certainly help in an autocross situation AS LONG as you use a stiff rollbar and/or stiff springs, and don't care about tire scrub. For the street I think it's inferior to the dropped spindles and tall balljoint, which is the case I've been making. The dropped spindles and tall balljoint still have good camber gain, a better roll center, and virtually no tire scrub.

However, all that said, the C4 suspensions are still the clear winner, which doesn't surprise me. They're 30-40 years newer!! And they're a lot lighter and cooler-looking than the stock parts. :) :) :)

Laz...is the scrub radius on the C4 front ends positive or negative? I've read that one thing GM was aiming to do with the later C4 front suspension change was improve split mu braking. If the scrub radius went a little negative vs. the early C4 that would probably explain why.

I thought long and hard about trying the longer balljoints on my '56 but in the end, I just got tired of throwing money at the stock configuration only to be disappointed. The other thing not mentioned in any of these geometry conversations is the feel of the steering. While that is very subjective, I can't see even a 500 box being better or even equal to a late model front R&P design. I never liked the way the 605 box felt (it was almost worse than the stock box), but even the 500 box I didn't really like (although it was hands-down better than the 605 I had in it).

[chevynut]

It pretty much all goes out the window, if the weight distribution is overly front heavy, as for as cornering speeds go. The C4 had a lot of engine setback, compared to the tri five.

No it doesn't "go out the window". The same suspension geometry still applies regardless of weight distribution. And the weight distribution is the same in a tri5 with the stock setup or the C4 setup. Again, you want to confuse the issue with irrelevant information. We're not talking about C4 Corvettes, we're talking about making a tri5 handle better. ;)

The C4 Corvette engine was set back 3-4 inches further than it can be in a tri5, unless you're willing to cut the tri5 firewall. Most guys don't want to do that.....at least not that much. Setting the engine back that far creates a lot of other issues. The C4 Corvette engine was also offset about 1" to the passenger side for driver footwell clearance.

[chevynut]

Laz...is the scrub radius on the C4 front ends positive or negative? I've read that one thing GM was aiming to do with the later C4 front suspension change was improve split mu braking. If the scrub radius went a little negative vs. the early C4 that would probably explain why.

Chad, the SAI on the late C4 is significantly higher than it was on the early C4. Based on my measurements, it's around 18 degrees versus the 8.744 degrees on the early C4 suspension. That results in a negative scrub radius with a 50mm offset wheel. I don't know what "split mu braking" is. :confused:

[hutchenc]

Thanks Laz...that makes sense (the SAI affecting the scrub radius...making it closer to zero, or even negative).

Split mu (mathematic symbol for friction maybe?...the lowercase Greek letter m or "mu") braking is when one side of the car, let's say the driver's side has a dry surface, and the passenger side is on ice (like ice that forms on a shoulder) or maybe even gravel which is not at all uncommon. If the car has a positive scrub, the tire that grips (the driver's side) during braking, which is force pushing back against the tire/wheel, will rotate a bit around the positive scrub radius and effectively toe out if you have a positive scrub which will (possibly) steer the car into...you got it...the center of the road or the oncoming lane of traffic. If you've got negative or close to zero scrub radius, that doesn't happen. I think that's partially why GM did that in '88. Also...I think the advent of ABS also necessitated going to a near zero or negative scrub radius.

Having scrub near 0 also makes the car track straighter I believe.

Now I'm curious what adding C5 brakes will do to scrub radius. I feel like the rotors for the C5 changes the wheel mounting surface and push it out (maybe) which would, all things being equal, increase the scrub radius right?

[chevynut]

Now I'm curious what adding C5 brakes will do to scrub radius. I feel like the rotors for the C5 changes the wheel mounting surface and push it out (maybe) which would, all things being equal, increase the scrub radius right?

Thanks for the education in split mu braking...never heard of that before ;).

I don't know why C5 brakes would change the WMS width at all. I don't think the rotor is any thicker at the mounting area but it's possible. If anything it might change it 1/16". However, if the wheel moves outboard on the late spindle I think the scrub radius decreases since it's negative stock. I wish I knew what the exact factory spec was on the SAI. Not sure why they picked 8.744 degrees for the early spindle....seems like an odd number.

I don't know if you've found any adapters for the C5 brakes but I ran across these the other day. You can even put 14" ZO6 brakes on a C4 spindle with these relatively inexpensive kits: http://www.flynbye.com/catalog/c8_p1.html


http://www.flynbye.com/sitebuildercontent/sitebuilderpictures/C6ZO6.jpg

http://www.flynbye.com/catalog/c8_p1.html

[55 Rescue Dog]

The point I was attempting to make, was that perfect front geometry will not always get you perfect handling, if the weight distribution is bad. A modified stock front suspension with a aluminum LS motor would not need as much camber gain, or as high of a roll center, as a C4 suspension would, with a BBC perched on top of it.

[chevynut]

The point I was attempting to make, was that perfect front geometry will not always get you perfect handling, if the weight distribution is bad. A modified stock front suspension with a aluminum LS motor would not need as much camber gain, or as high of a roll center, as a C4 suspension would, with a BBC perched on top of it.

I'm not sure what that has to do with anything, but let's compare apples to apples here. An aluminum LS engine in a chassis with C4 suspension would still perform better than the same engine in a chassis with the modified stock suspension. How about an aluminum BBC? You can come up with all sorts of combinations to make your case.

Keep in mind that you're also looking at a large difference in roll moment arm length between the two suspensions in a tri5, so the BBC isn't handicapped as much as you think. From numbers I've found an aluminum head iron BBC weighs 620 pounds without any accessories, just the basic engine with heads and intake. The LS engine weighs around 420 pounds, for a 200 pound difference. The bare blocks weigh 268 and 106 pounds, respectively, so that seems reasonable since they both have aluminum heads. I don't know actual weights but let's go with that.

So assuming a 620 pound aluminum headed BBC in a C4 chassis it's roll moment would be 8190 inch-pounds per my numbers above. The 420 pound aluminum LS engine in the dropped spring case would be 8122 inch-pounds. That's only a 1% difference. That doesn't even consider the movement of the roll center as the suspension compresses, which is much less with the C4 suspension, though the CG drops so the moment arm decreases. I was using static roll center moment arm for the calculations. And as far as the weight difference, the full C4 suspension almost eliminates the ~200 pound weight advantage of the LS engine. So all that kind of shoots your point out of the water, imo. ;)

The fact is in autocross you need lots of torque over a wide RPM range. A BBC will give you that torque easier than most any LS engine will. Show me one naturally aspirated LS engine that achieves the torque levels of a big-inch BBC and I'll show you a BBC that will deliver more.

You're also ignoring the other deficiencies of the stock suspension such as a bad scrub radius, very low SAI, little anti-dive, higher un-sprung weight, not to mention the differences between an IRS and solid rear axle. Virtually every high performance car nowadays has all aluminum suspensions and an IRS. There's a reason for that.

Most of us aren't building all-out race cars to get every bit of handling performance and power that we can. If we were, we'd probably do a lot of things differently. Most guys are looking for a car that feels and handles like a modern car with good reliability, performance, and aesthetics at a reasonable cost.

[55 Rescue Dog]

I thought power would be a big missing piece of the puzzle, when autocrossing my stock 97 C5 on Z06 size tires last year, only to find out I couldn't use much more than half the available power. I think I could have matched the C5 with my 77 VW Rabbit I autocrossed 30 years earlier, with 1/4 the power. And that car had major negative camber gain, with one rear wheel off the ground! I autocrossed in 1983 in a VW GTI, within 1 spot of Randy Probst, the factory Corvette race driver. It was the SCCA nationals in Salina Kansas, in 1983.

[Rick_L]

I think your comments show why many talk autocrossing down, saying it's typically too tight of a course for big power or even big cars. But that's also why it exists, it doesn't require nearly as much space as alternatives, so it can be set up as a side event at other events.

What's the next step up short of a full road race course?

[chevynut]

I didn't even know autocross existed in 1983. :)

[55 Rescue Dog]

I didn't even know autocross existed in 1983. :)
I think it started around 1972. I remember somebody flipping a swing axel Triumph Spitfire in a parking lot, with pylons, 1/2 mile from where I live now, back when I was in high school at the time, which I thought was pretty cool.

[hutchenc]

Thanks for the education in split mu braking...never heard of that before ;).

I don't know why C5 brakes would change the WMS width at all. I don't think the rotor is any thicker at the mounting area but it's possible. If anything it might change it 1/16". However, if the wheel moves outboard on the late spindle I think the scrub radius decreases since it's negative stock. I wish I knew what the exact factory spec was on the SAI. Not sure why they picked 8.744 degrees for the early spindle....seems like an odd number.

I don't know if you've found any adapters for the C5 brakes but I ran across these the other day. You can even put 14" ZO6 brakes on a C4 spindle with these relatively inexpensive kits: http://www.flynbye.com/catalog/c8_p1.html


http://www.flynbye.com/sitebuildercontent/sitebuilderpictures/C6ZO6.jpg

http://www.flynbye.com/catalog/c8_p1.html


Yeah I've seen all sorts of options for C5 brakes on the C4
spindles. I thought about going with the C6 ZO6 brakes but I'd have to run 18" wheels I think...maybe even 19's neither of which I'm really interested in. You can swap C5 and C6 brake calipers on any C5 application so I think I'm just gonna do that. Apparently the C6 calipers are a little stiffer than the C5's and they're not any more expensive either. I hear you can also run a hybrid C4/C5 setup where you use the 13" C4 rotor and a C5/6 caliper (with the adapter), but apparently the C5 rotors are cheaper to replace than the 13" C4 rotors are.

BTW...there are CAD drawings out there for the C4 adapter bracket. http://www.grumpysperformance.com/C5_caliper_upgrade.jpg You might think about offering that as option for your future customers if you could find someone to make those. I bugged my pop about it once...he didn't seem too interested, but he might be if there were a market.

[Custer55]

It pretty much all goes out the window, if the weight distribution is overly front heavy, as for as cornering speeds go. The C4 had a lot of engine setback, compared to the tri five.

The weight distribution of the C4 and a Tri 5 is actually very close so that shouldn't be an issue. Before I started my project I weighed both our 90 Corvette and my 55 Chevy 2 door sedan and the distribution front to rear was within 1 or 2% of each other. I'll post the actual numbers if I can remember where I wrote it down. (Both were weighed on the same scales at the local speedway, separate scales for each wheel). I moved my engine forward 3/4" and the radiator will be moved to the 6 cylinder position but the Corvette suspension parts will be lighter. I do plan to weigh my 55 again when I can drive it to see what the actual difference is. Hopefully that will be sometime in April or May.
Brian

[chevynut]

Yeah I've seen all sorts of options for C5 brakes on the C4
spindles. I thought about going with the C6 ZO6 brakes but I'd have to run 18" wheels I think..

I'll probably run 18's all around when I finally get a new set of custom wheels. I wonder if they'd work with 18s?.


Apparently the C6 calipers are a little stiffer than the C5's and they're not any more expensive either.

I'm assuming the 14" brakes would use the same caliper as the 13" application, just a different bracket and rotor?


I hear you can also run a hybrid C4/C5 setup where you use the 13" C4 rotor and a C5/6 caliper (with the adapter), but apparently the C5 rotors are cheaper to replace than the 13" C4 rotors are.

I'm pretty sure my 13" Baer rotors are the same configuration as the OEM J55 C4 Corvette Rotors. I may upgrade to the C6 calipers at some point, since my Baer upgrade kit has PBR 2-piston calipers very similar to the stock C4 ones. The rotors are 2-piece which I like. One issue with a C5 upgrade is what to do with the rear rotors so they match the front.


BTW...there are CAD drawings out there for the C4 adapter bracket. http://www.grumpysperformance.com/C5_caliper_upgrade.jpg You might think about offering that as option for your future customers if you could find someone to make those. I bugged my pop about it once...he didn't seem too interested, but he might be if there were a market.

Maybe you could ask him what the cost would be to make a pair. I could have blanks laser cut to minimize machining. I think I could sell quite a few of them to my customers.

[chevynut]

The weight distribution of the C4 and a Tri 5 is actually very close so that shouldn't be an issue.

I've actually had people ask me if I thought the aluminum Corvette parts were strong enough for these "heavy" cars. :) A C4 Corvette weighs about 3350 pounds.


Before I started my project I weighed both our 90 Corvette and my 55 Chevy 2 door sedan and the distribution front to rear was within 1 or 2% of each other.

It's cool that you have the Corvette and your 55 with the Corvette suspension. It will be interesting to hear your feedback on how the 55 compares when it's finished.


I do plan to weigh my 55 again when I can drive it to see what the actual difference is. Hopefully that will be sometime in April or May.
Brian

I would like to see those numbers. The guy with the blue Nomad weighed it on 4-point racing scales. His car turned out heavier than I thought it would, but he did add quite a bit of extra stuff to it like A/C power windows, Dynamat, bucket seats, console,etc. It weighed 1870 in the front, and 1816 in the rear with an LS1/4L60E and a full tank of gas. That's 3686 pounds total compared to a stock (56) Nomad at 3600 total, 1830 front and 1770 in the rear. I couldn't find specs for a 57.

[hutchenc]

I'll probably run 18's all around when I finally get a new set of custom wheels. I wonder if they'd work with 18s?.



I'm assuming the 14" brakes would use the same caliper as the 13" application, just a different bracket and rotor?



I'm pretty sure my 13" Baer rotors are the same configuration as the OEM J55 C4 Corvette Rotors. I may upgrade to the C6 calipers at some point, since my Baer upgrade kit has PBR 2-piston calipers very similar to the stock C4 ones. The rotors are 2-piece which I like. One issue with a C5 upgrade is what to do with the rear rotors so they match the front.



Maybe you could ask him what the cost would be to make a pair. I could have blanks laser cut to minimize machining. I think I could sell quite a few of them to my customers.

I don't think the C5/6 calipers and the C6 ZO6 calipers will interchange, but I could be wrong. It's appears that the C6 ZO6 calipers can clear an 18" wheel, but not all. Kore3 has great info on their site here: http://www.kore3.com/tech.php#fitment_templates Look at the wheel fitment templates. These guys make quality stuff...too bad they don't offer anything for C4's. I do see that they have a tri-five hub for the stock spindles...kinda interesting.

I'll bug my pop...he's pretty busy with a DoD contract right now, but it might slow down a little bit in a month or so.

[chevynut]

55 rescue dog said on another thread....

"So, what exactly is the perfect camber gain? Sure, it is a big factor at max g's in a corner, dependent on body roll, etc. But it has no benefit going straight down the road, or low G cornering speeds, and cannot possibly help under heavy braking loads either. Camber gain it seems, is always scrubbing the tire in, and out, even when not needed. It is all a balancing act, depending on it's intended use. "

"Perfect" camber gain, as I understand it per my research on the subject, is such that the tire patch is perfectly flat on the road as the body rolls. That gives maximum traction. 2" of body roll where one side is up 1" and the other down 1" is about 1.6 degrees. As far as I know there is no benefit to camber gain going straight down the road. Tires don't always scrub with camber gain and you probably don't get 2" of suspension travel that often going straight.

The C4 suspensions have very little tire scrub with 2" of suspension travel from ride height with a level lower a-arm, 0.027" for the early suspension and 0.070" for the late suspension per my calculations. Tire scrub has been my point on the deficiencies of the 2" cut springs. The lower balljoint moves in and out a lot, and the camber gain doesn't offset that movement entirely. You get a net 0.22" tire scrub with the extended balljoint, 2" cut springs, and 2" of compression travel with the stock spindle and a-arms.

As for heavy braking, again you make my point on the benefits of the C4 suspension :). They have more anti-dive which limits front end drop under heavy braking, like you would see in autocross.

You can see all my tire scrub and camber gain calculations in the results above, if you care to review them.

[Rick_L]

How do YOU know when the tire is flat to the ground? Show me what the ideal camber gain is for a specific example.

It is totally track/road/tire dependent. You don't know without measuring the temperature across the tire. You also need to know how stiff the tire is among many other things if you are even going to attempt doing it on paper.

[55 Rescue Dog]

A lot of cars handle great with positive camber gain, like the MacPherson struts on so many cars, like my BMW M roadster, which will run circles around my C5. And, while anti-dive can be a good thing on paper, without trying it how much is best? Weight transfer can help under braking, and steering. Too much anti-dive can cause the suspension to bind up, and effectively increase the spring rate promoting understeer at corner turn in. Same with too much roll stiffness if the roll center, is too high, or springs, and bars too stiff. At some point the only way is to test drive, and tune the suspension, with the right combination of parts, for any given design.
And, it doesn't matter how well the front works, if it is not in harmony with the rear suspension. The Tri-5, and C4 CG heights are not the same either. How does that compute? And, what is the effect from going to coil overs from the traverse springs, that have more roll stiffness?

[chevynut]

It's pretty clear (to me) that when a car's chassis rolls 2 degrees you have to have 2 degrees of negative camber to offset the chassis roll if you have any hope of keeping the contact patch flat. As a first order that's what you need, imo. Zero or positive camber isn't going to work. Of course there are other factors, like centrifugal forces that put side loads on the tire but first you have to cancel the body roll. Positive camber is going in the wrong direction to offset chassis roll and side loads. Of course serious racers try to make adjustments to compensate for other factors but most people don't do that on their cars.

RD you always asks these rhetorical questions like "how much is best?" Tell ya what, RD, why don't you go figure it out since you think it can't be done on paper or with any logical engineering thought process. No amount of analysis seems to convince you of anything since you seem to think engineering doesn't work. Engineers who design modern suspensions use dynamic suspension analysis software to design suspensions and the trends are well-known but you don't seem to want to believe it. So go drive everything out there and report back on how well it works. Hell, you wouldn't even go drive a C4 Vette to see what it drives like! :) So maybe you should go out there and "try everything" and design your own suspension that works for you. ;)

And I have no clue what makes you think the stock C4 spring has more roll stiffness than a coilover. Show me your analysis. It doesn't make sense to me. Both springs apply a force to the rear knuckle and the more force downward the more roll stiffness. It doesn't matter how you do it.

A McPherson strut suspension doesn't have to exhibit positive camber gain, it depends on the angle of the lower arm to the strut. And if you think positive camber gain is a good thing for a race car on a turn, good luck racing! :)

[chevynut]

The bottom line is that I think it's pretty easy to get 2" of body roll on a car and for a tri5 that's over 1.5 degrees. So a minimum of 1.5 degrees of camber is needed to keep the tire flat on the road. Both C4 suspensions accomplish that and improve many other deficiencies of the stock tri5 chassis and suspension. To account for tire sidewall distortion due to side-loading more camber is probably needed. That's why low profile tires work better for performance....the sidewall doesn't flex as much.

We can nitpick about tweaking it to "perfection", but for practical purposes the above is a pretty good starting point. It's not that easy to change camber gain on a car, you can only change initial camber by using shims or adjustable a-arms. Changing ride height can put the suspension in a different part of the camber curve, but there's a limit to what can be done and it can throw other things out of whack.

RD, please explain to me why you think the stock C4 spring is better at reducing body roll than a coilover. I've explained the fallacy in your argument before, but you don't seem to accept it. ;)

[55 Rescue Dog]

The bottom line is that I think it's pretty easy to get 2" of body roll on a car and for a tri5 that's over 1.5 degrees. So a minimum of 1.5 degrees of camber is needed to keep the tire flat on the road. Both C4 suspensions accomplish that and improve many other deficiencies of the stock tri5 chassis and suspension. To account for tire sidewall distortion due to side-loading more camber is probably needed. That's why low profile tires work better for performance....the sidewall doesn't flex as much.

We can nitpick about tweaking it to "perfection", but for practical purposes the above is a pretty good starting point. It's not that easy to change camber gain on a car, you can only change initial camber by using shims or adjustable a-arms. Changing ride height can put the suspension in a different part of the camber curve, but there's a limit to what can be done and it can throw other things out of whack.

RD, please explain to me why you think the stock C4 spring is better at reducing body roll than a coilover. I've explained the fallacy in your argument before, but you don't seem to accept it. ;)
BTW I have driven and autocrossed a C4 Vette before back, in 1990. It was okay back then, but far from perfect now. Why do the engineers at GM still use the traverse spring on the C7, if it is so bad? They can even eliminate the rear sway bar, because it naturally reduces the roll rate. I never said a C4 conversion was a bad idea, but if I was building, and selling them, I would drive one for sure, and not try and convince everyone how great it looks on paper. Watching "Engineering worst disasters" is always interesting.
https://en.wikipedia.org/wiki/Corvette_leaf_spring

[rockytopper R.I.P 5-13-2017]

Wow I go on vacation to unwad my panties and this thread still goes south and goes off topic. Guess it's time to start another one lol....
We will just have to settle this like gentleman at the track some day.... Should not be to long looks like one of Cnuts customers is about to go live.
http://www.trifive.com/forums/showthread.php?t=156365

Rick the butt dyno invitation is still open for June.......

[rockytopper R.I.P 5-13-2017]

Laz your work is being showed off on the FB nomad page just above your incredible polished chassis if you care not to log into old site. The 57 looks real nice and says guy built in his on garage including paint. Running an LS engine. Looks pretty sweet even with corvette wheels lol.

[chevynut]

As I was working out at the gym today I started thinking about these suspensions and it occurred to me that camber gain with the wheels pointed straight forward doesn't nearly tell the whole picture when it comes to suspension geometry.

When you're going around a corner, not only is the suspension compressed but the spindle is rotating around the balljoints and caster and SAI play a big part in how that wheel leans in a turn. We've only looked at SAI in terms of scrub radius and how it positions the upper balljoint and a-arm.

Imagine a spindle with no SAI and no caster. All you get is camber gain from movement of the a-arms and no change as the wheel turns. That's all we've analyzed so far.

Now imagine the same situation with no SAI but 6 degrees of caster. Assume no a-arm movement. As that wheel turns 90 degrees, you get 6 degrees of negative camber. Of course it doesn't turn 90 degrees when you steer, but you get the idea. The camber gain is more with more caster and I assume it's linear with degrees of turn.

Now let's look at SAI. Let's assume no caster, but SAI of 10 degrees. Again assume no a-arm movement. As the wheel turns, it leans outward at the top. When turned 90 degrees, you'd have 10 degrees of positive camber.

So this tells me that a car with 6 degrees of caster, SAI of 10 degrees, and an a-arm setup that gives 1.5 degrees of camber at 2" compression will actually end up with more camber than we've reported here. I'm going to go out on a limb and estimate that such a suspension when compressed 2" and turned 10 degrees would end up with somewhere in the range of .67-1.1+1.5 or 1.07 degrees of total negative camber excluding static camber. I'm not sure how to correctly calculate it but that's a stab at it.

Now, looking at the inside wheel in a turn caster causes positive camber, which helps plant the tire on that side. SAI also results in positive camber which is good on that inside wheel, even though that's not the tire with the big load on it. At 2" of extension I think most suspensions will cause some positive camber gain. So the net result is positive camber on the inside tire, which also helps in a turn. Perhaps this is why SAI is increased for more modern suspensions.

So, caster and SAI need to be factored in since the wheels are turned in a corner, when the suspension is compressed.

[rockytopper R.I.P 5-13-2017]

Link?


Nick you can see it on the other site the link is posted above. If you wish to see it on facebook you need to join the Tri-five Chevy Nomad Only group. It's a brite Red 57 nomad you can't miss it lol....

[NickP]

Nick you can see it on the other site the link is posted above. If you wish to see it on facebook you need to join the Tri-five Chevy Nomad Only group. It's a brite Red 57 nomad you can't miss it lol....

I suspicioned that you were talking about Calvin's 57. You do realize, that is not one of Classic Edge Design's chassis.

[rockytopper R.I.P 5-13-2017]

I suspicioned that you were talking about Calvin's 57. You do realize, that is not one of Classic Edge Design's chassis.

the OP that posted it says it is. So I just assumed it was.

[chevynut]

Why do you guys take this off-topic when I specifically asked not to do that?

Do you guys have any comments on the suspension analysis, or are you just wanting to BS? ;)

Rocky, did you read my summary of the different suspension setups? I concluded that yours is pretty darn good for autocross racing, but has some issues for a driver. You get quite a bit more tire scrub (more wear) than the other options, and suspension travel is severely limited. Also, your design has a lot longer roll center moment arm so you'll need larger swaybars and/or stiffer springs the latter of which will reduce ride quality.

[rockytopper R.I.P 5-13-2017]

Certainly understand however he was corrected by the owner and later clarified by the chassis builder. No big deal though.

LOL I just read it to the end, looks like he stole your glory that's your baby under there.!!!! Still a real nice nomad.....

[chevynut]

BTW I have driven and autocrossed a C4 Vette before back, in 1990. It was okay back then, but far from perfect now.

And what do you consider "perfect" now, and how does it compare to the C4 suspension technically? The C5/6 double a-arm rear is better than the C4, but try to package that into a Tri5 at a reasonable cost. Do you wonder why nobody's doing it? Sure you can go with an AME IRS for $9500 if you want to.


Why do the engineers at GM still use the traverse spring on the C7, if it is so bad?

Who said a stock C4 spring is "bad"? Show me where I ever said that. Why do you take what I said and infer something else? You made the comment that coilovers decrease the roll stiffness compared to the stock spring, and I disputed that and explained why they don't. I noticed you didn't address why you think that's so. So go ahead...try to explain it.

I believe one reason GM uses the composite spring instead of coilovers like most other high-end car manufacturers is the cost. The spring is probably cheaper than coilovers. Also, the composite spring can be preloaded to result in a softer wheel rate. Packaging is another consideration. Tell me why no other exotic or high end sports car uses that type of spring. You seem to avoid those discussions.


They can even eliminate the rear sway bar, because it naturally reduces the roll rate.

Then why does EVERY C4, C5, C6, and C7 Corvette still have a sway bar? It's because the anti-roll effect of these springs is very small. The spring has to flex between the mounting brackets where it's the stiffest. If a customer of mine wants to use the stock spring, he can do that if he wants. The stock spring has a lot of limitations, one being the ability to easily adjust ride height in the front.


I never said a C4 conversion was a bad idea, but if I was building, and selling them, I would drive one for sure, and not try and convince everyone how great it looks on paper. Watching "Engineering worst disasters" is always interesting.

My customers are a better source for feedback than I am as others have explained to you. If I drove one and told you how good it was, you'd complain that I was biased and you wouldn't believe my evaluation. But for some reason you don't want to get feedback from customers that are actually driving cars with my chassis regularly. There are hundreds of Newman frames out there and the feedback on them is great. There's no reason to believe mine is any different, as I've tried to explain many times but you don't seem to get it. Any C4 conversion out there is going to drive about the same...the biggest difference imo is the coilover versus stock spring, and my design allows the customer to choose which one he wants.

Of course you don't think any engineering can be done "on paper" because you've never done it and don't understand engineering principles. That's been obvious in every discussion we've had whether it's strength of materials or suspension design. I don't see you offering any analysis, just your opinions.

[rockytopper R.I.P 5-13-2017]

Why do you guys take this off-topic when I specifically asked not to do that?

Do you guys have any comments on the suspension analysis, or are you just wanting to BS? ;)

Rocky, did you read my summary of the different suspension setups? I concluded that yours is pretty darn good for autocross racing, but has some issues for a driver. You get quite a bit more tire scrub (more wear) than the other options, and suspension travel is severely limited. Also, your design has a lot longer roll center moment arm so you'll need larger swaybars and/or stiffer springs the latter of which will reduce ride quality.


Yes I did and I cannot argue against your conclusion. I'm glad to see that at least you can see now it is pretty good setup for the money. That's all I really ever meant or try to imply. But it isn't a c4 and never will be. I will say that I have had no issues with excessive tire wear, the nitto 555 is a performance tire and doesn't get long tire wear anyway. I have worn the rears out smoking them faster than the fronts are wearing at least on the first set and they saw a lot of ax action and notable wear on the edges after the events, I'm currently on the second set sense car was built no ax. It was once said that with the aggressive alignment I have that tire wear would actually be less if your driving was mostly around town turning more than straight line driving. Kinda made sense. I do commute in it 120 miles a day interstate driving hasn't seemed to be an issue. Maybe if I was running a long life all season tire you would not get as much out of them with my setup as stated.

I will also note that the bolt on setup I'm going with cost approximately 10k for a rolling chassis. That includes all new components, sway bars, springs, 800$ varishocks, 500 steering box with 4 wheel disk and complete brake system hydro boost to fire wall and 4 brand new wheels and tires and a beefed up original rearend or after market 9 bolt cost about 500$ more than the stock rebuild with limit slip added. Still undecided on the rearend
Rocky

[Rick_L]

Why do you guys take this off-topic when I specifically asked not to do that?

Why? We've asked you not to be rude and arrogant and you don't stop.

[55 Rescue Dog]

And what do you consider "perfect" now, and how does it compare to the C4 suspension technically? The C5/6 double a-arm rear is better than the C4, but try to package that into a Tri5 at a reasonable cost. Do you wonder why nobody's doing it? Sure you can go with an AME IRS for $9500 if you want to.



Who said a stock C4 spring is "bad"? Show me where I ever said that. Why do you take what I said and infer something else? You made the comment that coilovers decrease the roll stiffness compared to the stock spring, and I disputed that and explained why they don't. I noticed you didn't address why you think that's so. So go ahead...try to explain it.

I believe one reason GM uses the composite spring instead of coilovers like most other high-end car manufacturers is the cost. The spring is probably cheaper than coilovers. Also, the composite spring can be preloaded to result in a softer wheel rate. Packaging is another consideration. Tell me why no other exotic or high end sports car uses that type of spring. You seem to avoid those discussions.



Then why does EVERY C4, C5, C6, and C7 Corvette still have a sway bar? It's because the anti-roll effect of these springs is very small. The spring has to flex between the mounting brackets where it's the stiffest. If a customer of mine wants to use the stock spring, he can do that if he wants. The stock spring has a lot of limitations, one being the ability to easily adjust ride height in the front.



My customers are a better source for feedback than I am as others have explained to you. If I drove one and told you how good it was, you'd complain that I was biased and you wouldn't believe my evaluation. But for some reason you don't want to get feedback from customers that are actually driving cars with my chassis regularly. There are hundreds of Newman frames out there and the feedback on them is great. There's no reason to believe mine is any different, as I've tried to explain many times but you don't seem to get it. Any C4 conversion out there is going to drive about the same...the biggest difference imo is the coilover versus stock spring, and my design allows the customer to choose which one he wants.

Of course you don't think any engineering can be done "on paper" because you've never done it and don't understand engineering principles. That's been obvious in every discussion we've had whether it's strength of materials or suspension design. I don't see you offering any analysis, just your opinions.
I was just trying to have a discussion, and don't have to prove anything, and I didn't say YOU, to you, 16 times like you just did to me. So what, if I like proof, over analysis, and I didn't bring up somebody else's chassis design to try and make any points in the discussion either. It took a lot of engineering to land on the moon, but would have not meant much, if they never made it there.
As far as engineering goes, I think what matters more than, how much you know, is the ability to learn.
"Form follows function"

[chevynut]

I didn't say YOU, to you, 16 times like you just did to me.

Your implication is clear, based on other things you've said before. You have insisted that I should have driven a car with one of my chassis so I could give feedback. And then when you make the same comment you act like it's not directed at me? Gimme a break. My happy customers are my testimony.


So what, if I like proof, over analysis,

Analysis IS proof to most people who understand engineering principles. You've provided no proof of anything. I've done all sorts of calculations, and you say they don't prove anything. I've shown proof of the performance of the C4 suspension by showing Kyle Newman's autocross results and videos. Nothing satisfies you, apparently.


It took a lot of engineering to land on the moon, but would have not meant much, if they never made it there.

But the fact is they DID make it there. And now they've landed on Mars. There's your proof that engineering analysis and calculations WORK. Corvettes have been built, driven millions of miles, and raced. They engineered them before they went into production. I'm betting not much real track testing went into the suspension designs. Even if they did, it just proves that they work. I'm not re-designing them.

And I have asked you what makes the C5/6 or C7 front suspension design better than a C4...you have no answers. I don't think you know the difference.


As far as engineering goes, I think what matters more than, how much you know, is the ability to learn.

If you want to learn and have some questions about something not on this topic, start your own thread and ask them. If you have on-topic questions, then ask them and discuss it instead of going from topic to topic and asking rhetorical questions. It's interesting that you raise all these issues and I try to address them, then you never acknowledge anything I said. You didn't even address the fact that ALL corvettes still have swaybars despite your claims that they can be eliminated with the transverse spring. You haven't addressed your insistence that roll stiffness decreases with coilovers. On the other thread you didn't comment on my stress calculations, just threw a bunch of "what ifs" out. You bounce all over and don't address the topics.

What I find MOST amusing is that you started a thread a while ago asking for feedback on C4 conversions. You wouldn't listen to the guys like Jim's57 and others who have actually driven these cars, nor did you want to call my customers and talk to them, so I suggested that you drive a C4 Corvette. Not once did you so much as say you have even driven one, but now you claim you even RACED one for years. So since you allegedly did so much "testing" why can't YOU tell US how good or bad they work and where the deficiencies are? ;)

[chevynut]

Why? We've asked you not to be rude and arrogant and you don't stop.

Go F* yourself Rick.

Funny how someone as rude and arrogant as you can say that.

[chevynut]

Yes I did and I cannot argue against your conclusion. I'm glad to see that at least you can see now it is pretty good setup for the money. That's all I really ever meant or try to imply. But it isn't a c4 and never will be.

I was surprised by the results as I said. There are deficiencies but it's a big improvement.


I will say that I have had no issues with excessive tire wear, the nitto 555 is a performance tire and doesn't get long tire wear anyway. I have worn the rears out smoking them faster than the fronts are wearing at least on the first set and they saw a lot of ax action and notable wear on the edges after the events, I'm currently on the second set sense car was built no ax.

So are you racing the Nomad now? The Olds has a totally different suspension setup and I would hesitate to say you'll get the same results with the Nomad without analyzing the Olds suspension.


I do commute in it 120 miles a day interstate driving hasn't seemed to be an issue.

In the Nomad? I didn't think you were driving it yet. If you are, that's great.


I will also note that the bolt on setup I'm going with cost approximately 10k for a rolling chassis. That includes all new components, sway bars, springs, 800$ varishocks, 500 steering box with 4 wheel disk and complete brake system hydro boost to fire wall and 4 brand new wheels and tires and a beefed up original rearend or after market 9 bolt cost about 500$ more than the stock rebuild with limit slip added. Still undecided on the rearend
Rocky

You could have done a complete C4 chassis for close to that price. ;)

[55 Rescue Dog]

For those that missed the link on my previous post. The traverse spring does resist roll, and a rear sway bar, IS NOT used on the rear of the base C7 Corvette. GM actually first used a traverse spring on the 64 Corvair rear to try and fix their "engineering mistake" on the swing axel, but it was too late by then.
https://en.wikipedia.org/wiki/Corvette_leaf_spring
I don't need to be an engineer to see, that when coil overs are angled inboard towards the center of the car, that the roll stiffness is decreased because of the moment arm. I also have found out the hard way, when you increase roll stiffness, it just make the chassis twist, and flex more, and the benefit of roll stiffness turns into shudders through the car instead. Chassis torsional stiffness was a major weak point in the C4 Corvette. Even worse, with the targa top removed. The stock tri-five didn't need much torsional stiffness, because it had very little roll stiffness, but I'm sure it rode nice on rough pavement, and dirt roads that it was designed for.

[55 Rescue Dog]

And for what it's worth, although far from perfect, I learned a few things from building one car. I would have done some things different after driving it. Despite ZERO engineering, and only built off the top of my head, it drives, and handles pretty good. No discernable chassis twist for sure, which gives great feedback on the suspension.
http://bangshift.com/bangshiftapex/car-feature-street-legal-circle-track-camaro-unique-homebuilt-corner-burning-monster/

[55 Rescue Dog]

Again, no engineering, but I did raise the front roll center, to I have no idea what. Small front sway bar, no coil overs, leaf spring rear, with no rear sway bar, all old school, and it corners very flat. Even though I dialed in a lot of camber gain, that was not really needed. It does have a ton of scrub radius too, but it still works, somehow. 10 inch engine set-back, dropped low, helped too. The biggest regret, was not building it to fit a 55, which crossed my mind several times.
http://www.myrideisme.com/Blog/building-dream-car-dirt-track-racer-car/

[Rick_L]

Somehow I don't think anything like that is most guys' idea of a high performance street machine.

If you like it, fine - but I don't think most will. No doubt you put a lot of effort in it.

A car like that is nowhere near a 55-57 with a C4 suspension. Or any other suspension most would use.

[Maddog]

From start to finish-pure hotrodding. Love it or hate it. Not my cup of tea but my hats off to you and your skills.

[rockytopper R.I.P 5-13-2017]

Laz does it really matter if its an olds or a VW or even a new vet. Alignment and same tire would EQ about same wear on a freeway example straight line use not much suspension used dont really get your point. I'm thanking my swag method has more merit than the book work numbers your using another words my real world data with the Cutlass will not be much different on the Nomad. I really don't see why you would say it is as far as tire wear. Am I missing something?

[Custer55]

The weight distribution of the C4 and a Tri 5 is actually very close so that shouldn't be an issue. Before I started my project I weighed both our 90 Corvette and my 55 Chevy 2 door sedan and the distribution front to rear was within 1 or 2% of each other. I'll post the actual numbers if I can remember where I wrote it down. (Both were weighed on the same scales at the local speedway, separate scales for each wheel). I moved my engine forward 3/4" and the radiator will be moved to the 6 cylinder position but the Corvette suspension parts will be lighter. I do plan to weigh my 55 again when I can drive it to see what the actual difference is. Hopefully that will be sometime in April or May.
Brian

I found the book I wrote down the weights of Our 90 Corvette and my 55 Chevy.

For the Corvette the total weight was 3,413 lbs. minus my weight of 189 lbs. (there wasn't much room to get out of the car in the scale room, they weigh the race cars with the driver) for a total weight of 3,224 lbs. I can't say for sure how full the gas tank was but it was most likely at least a half to 3/4 tank.
Weight per wheel as follows: (this with my 189 lbs. in the car, obviously more left side weight added than right side)

left front - 919 lbs. right front - 856 lbs.

left rear - 865 lbs. right rear - 773 lbs.

This works out to a 52% / 48% front to rear weight distribution

For my 55 I was able to weigh it without being in the car, as a Tri 5 Chevy is much easier to get in and out of in tight quarters than a 90 Vette.
Again probably a 1/2 to 3/4 full gas tank.
Total weight was 3,410 lbs. This includes a couple of bag chairs and misc. stuff I keep in the trunk for car shows etc. Maybe an extra 20 to 30 lbs. at most.
Weight per wheel as follows:

left front - 890 lbs. right front - 878 lbs.

left rear - 805 lbs. right rear - 837 lbs.

This works out to a 51.8% / 48.2% front to rear weight distribution.

Nearly identical to our 90 Corvette. This is one of the reasons I decided to just use the stock Corvette springs and shocks.
It will be interesting to see where my 55 ends up weight wise with the new frame. I'm thinking it will be very close. The Corvette suspension parts should save 150 to 200 lbs. but I added the frame center section at about 70 lbs. or so, an extra cross member front and rear. a power steering pump, and the tilt steering column is heavier than the original. I have an aluminum water pump on order so that will save a couple of lbs. The engine is moved 3/4 forward, the radiator will be moved to the 6 cylinder position, and the gas tank is moved 3" backward. I am using the same engine and transmission though and probably the same radiator for now. I plan to upgrade to an aluminum cross flow when the budget permits.
Brian

[NickP]

Laz does it really matter if its an olds or a VW or even a new vet. Alignment and same tire would EQ about same wear on a freeway example straight line use not much suspension used dont really get your point. I'm thanking my swag method has more merit than the book work numbers your using another words my real world data with the Cutlass will not be much different on the Nomad. I really don't see why you would say it is as far as tire wear. Am I missing something?


https://scontent.fden3-1.fna.fbcdn.net/hphotos-xfp1/v/t1.0-9/10393897_1316903788336722_469271085258495538_n.jpg ?oh=e8dad285631b2b2bf33c9bf80341aec2&oe=5753A3E8

[rockytopper R.I.P 5-13-2017]

https://scontent.fden3-1.fna.fbcdn.net/hphotos-xfp1/v/t1.0-9/10393897_1316903788336722_469271085258495538_n.jpg ?oh=e8dad285631b2b2bf33c9bf80341aec2&oe=5753A3E8

LIKE LOL.... oh wait this isn't FB:)

[NickP]

Pretty close sometimes though.;)

[Classicgary]

I just want to make 2 comments, then sit back and watch:

1. C4 tech, is last century aka 1980's / 90's.
2. as long as the front suspension does what you want it to do, do the parts really matter?
meaning, C3 C4 C5 C6, aftermarket, space alien, cartoon, what ever. As long as what ever parts you are
using, if the car goes around corners, stops, goes straight, does it really matter what parts are used to get
the result? The result being: better than stock, reasonable dollars spent. Keeping up with the Jones-es. :)

[markm]

I just want to make 2 comments, then sit back and watch:

1. C4 tech, is last century aka 1980's / 90's.
2. as long as the front suspension does what you want it to do, do the parts really matter?
meaning, C3 C4 C5 C6, aftermarket, space alien, cartoon, what ever. As long as what ever parts you are
using, if the car goes around corners, stops, goes straight, does it really matter what parts are used to get
the result? The result being: better than stock, reasonable dollars spent. Keeping up with the Jones-es. :)

Agreed and I seriously doubt its possible to make one of these cars handle like a Camaro let alone a Corvette.

[hutchenc]

Agreed and I seriously doubt its possible to make one of these cars handle like a Camaro let alone a Corvette.

It's been proven that a C4 chassis'd tri-five can keep up with a C5 ZO6. You know...the ones that pull 1G on the skidpad blow away a stock C4 Corvette? That's not exactly bad. I think you guys are selling this really short. Is it a perfect race car?...probably not. Can you get a stock framed tri-five in the same ball park...I've yet to see that, but I'm not saying it's impossible. I think it's unlikely though.

There are plenty of Youtube videos of Kyle Newman tearing it up against new cars including a C5 ZO6 and high dollar Camaros. This is on a C4 chassis'd 55. Is a bit different than Lazlo's design...yeah, but it's still a C4 chassis. The platform is plenty capable of handling like a Corvette or a Camaro.

See here: https://www.youtube.com/watch?v=flE8BjXlr7U

Oh and keeping up with 1st and 2nd gen Camaros, and passing what looks like a C6 on a road course: https://youtu.be/psQHpPreF0M?t=6m14s

[Rick_L]

I was doing some reading over at pro-touring.com regarding SAI. Before we go too far I will say that I am just mentioning this and don't endorse it (or the opposite). Anyway, the article was discussing what happens as the wheels are steered that's influenced by SAI and caster. It suggests that the 18.5 degree SAI of the late C4 front suspension is way too much. Part of this is evidenced by the fact that the C5 spindle has much less SAI (also C6), i.e., they fixed it for the later versions.

Chevynut, have you read that article? Any comment? I know you posted a different article about this same subject, but I don't think it expressed an ideal range or what the limit might be.

Anyway, and this is kind of lame - just calling attention to it without having my own opinion yet. Hopefully I will. We're getting into 3D geometry here and that takes more tools to analyze.

[Rick_L]

This is the thread I'm referring to:

http://www.pro-touring.com/threads/111963-Front-Suspension-amp-Steering-Geometry-for-Track-Performance

[55 Rescue Dog]

This is the thread I'm referring to:

http://www.pro-touring.com/threads/111963-Front-Suspension-amp-Steering-Geometry-for-Track-Performance
Ron Sutton definitely has a grip on DYNAMIC handling, which is totally different than what it looks like on paper, which isn't pavement!

[oceangoer]

Well, thanks to all of you for the massive amount of work and effort.

Laz, Hit the Nail exactly on the Head !! He stated it's about "Driving our Tri5's", plain and simple.

I read many of these posts and others of various sus topics, but usually I don't sit down with Pen and Paper so I can understand each and every detail. I simply don't have the drive and time. But I do manage to learn a great deal and in the case of suspension details in post like this one and I do appreciate the info, I do often dig for an old dirty sus book for better understanding at times.

My '56 Chevy, I didn't install the C4 IFS & IRS at the time when We installed the LS1, T56 and Dutchman's 9 inch. I had all the parts, garage, tools,, at the time. But I did go with some bolt on's that,,, in the end is so much better than the stock Tri5 suspension. I still kinda regret not installing the C4 sus front and rear. But my little '56 is a very comfortable and responsive driver, even a few longer trips out of state. She's certainly not C4 quality, but close enough for this Car. The basic bolt on's are, Heidt's dropped spindles and polished S/S UCA & LCA, R&P rear steer, Helwig S bar, Wilwood 4 piston caliper kits,,,,

I live rural out in the forest area 25 miles out, and my sparsely populate hill is a twisty three mile hill uphill grade. I changed the front sus parts and braking so I can manage these Oregon Roads and the Freeways too. And, to safely navigate those unknown moments that pop up at us. Those are items like idiot or drunk drivers, Deer, Cougars, gravel in a corner, or a panic stop in a wet corner - This is what matters to me.

But, I'm just starting a full frame build with C4 sus front and rear and I'm helping my neighbor install C4 on both ends of his '57, now bare and naked frame. So I'm paying close attention. But I'm not going to mod major components !!

Yes, Like Laz I'm an Engineer (except retired), as was my Dad, Uncle and Grand Dad,, all which were Street Rod builder and drivers. So I grew up with this great past time and I keep it enjoyable. Being an Engineer, we all need details and no loose or unknowns... It drives me to learn the important details.

Just saying, thanks for all the effort every provides. I'll not need most of it, but I know where to look.....

Michael...

[chevynut]

Michael, I assume you know that I sell kits for installing an IRS and clips for the front. It could save you a lot of work. ;)

Here's another thread with a lot of C4 information:

http://www.trifivechevys.com/showthread.php/4234-Comparing-tri5-to-C4-front-suspensions

[oceangoer]

Laz,

Oh yes, I've reviewed all that I could find.

I have a front C4 suspension cross member that Don @ Flat Out Engineering made custom for my '37 Chevy build. I don't need a front clip for either project. I've fabricated a few frames, and many Mod's to C3 and C4 suspension over the years. But this is my first complete frame build utilizing C4 front and rear suspension. I've modified my C4 Convert sus a few times, and right now I regret installing the OEM rubber control arm bushings in 2000, there nearly frozen in place, prob due to not enough driving.

My life long friend Steve (ME) designed the frame rails on Solid Works. The frame rails will be Fabricated by AME, they have CNC square tubing benders that will bend the frame rails to spec, And We can drive up to their shop and pick them up - Hoping for a tour.. I also have Dutchman's 9 inch IRS Diffy and the dual tube cross member ready. I'm purchasing the frame rails from AME because I just don't feel like fab'g another pair this time...

We already have the C4 rear bat wing cross member with mounts in the '57 Desoto frame and the front late C4 engine cradle install is well under way. This frame is very similar to a Chevy Tri5 except for two major differences, at the rear kick up the 57 Desoto frame is approx. 1 1/2 inches narrower and the front (did) utilizes torsion bars so there's no large spring pockets.

The C4 with a Dutchman's 9 inch IRS diffy might be of interest to some Tri5 Chevy owners. I'll be happy to post progress with photo's. But I think that will prob get started in about 4 to 6 weeks. That's because of AME's lead time and getting the Frame Table set up over at my place after the C4 engine cradle brackets are finished, plus some added fudge time.

We'll set the LCA to "0" degrees and allow for 1/2 in tire compression on the light weight '37 and 1 inch on the '57. Seem correct too you ??

Michael

[chevynut]

OG, I've been to AME's plant and Art gave me a personal tour of the facility. They're great guys and I got to see the tube benders and frame jigs. That's been close to 10 years ago now so I'm sure things have changed. It was before they moved to make room for a highway.

I think I've seen another company that makes a bolt-in differential for a C4 IRS. But they're like $4500 if I remember correctly. A Dana 44 is a lot cheaper.

I think 1" is too much radius change for a loaded tire. For example, a 245/40-17 tire is 25.7" unloaded diameter and turns 810 revs/mile. That's a loaded 24.9" diameter. So the radius changes by .44". I think all of them will be on the order of 1/2" and imo if you're trying to get closer than that you're kidding yourself. :) If you feel the need to get closer, find a car with the tires you want to run, inflate the tires properly and measure it. :)

[oceangoer]

Laz,

Plant tour yes, I can't wait. I love plant tours of factory with automation !! I hope they let me snap a few photos...


Ride Height // Loaded Tire Height


I've always been fascinated with ride height and all of the complex geometry that results when People change it up or down. Even with the stupid ill informed decisions re ride height I'm amazed in that Cars that are raised or lowered 2 or 3 inches still can be driven reasonably well, 50 MPH or less. I wouldn't want to ride in one at high speeds. Both of these builds we are going to set the front an rear sus to as close as we can get to factory spec's


RE the compressed tire height, initially I had thought that a half inch would be appropriate for the '57 HT. But I measured the 2004 FRC ZO6 Le Mans Com, and the fronts are compressed a full inch, and I re-check just now.. The front tires are the originals, G/Y 265x40x17 run flats (detest this tire). And this model is supposed to be the lightest in the C5 ZO6 lineup..

I'll have to re-check the C6 wheels and tires for the '57. But I think the front are 255x40x18. We'll definitely install them and get a good loaded measurement. But, the motor sitting in the corner of the shop os a 392 Blown Hemi, and that's at least 350 pounds heavier than an all aluminum LS6.

I'm thinking stick with an inch for tire compression for the '57 HT.. Your Thoughts ???

I agree, getting the compress tire height within a "Half Inch" will be the goal. Plus, tire diameter and their compression numbers vary some.


So, the plan is to set the lower control height to a level LCA and Plumb, fore and aft, then finish the metal fabrication to bolt in the C4 engine cradle.

Don'y faint, but We are going to bolt the engine cradle in place initially. Once that done we will flip the frame over and finish anything on the bottom of the frame. Then the plan is to re-install the front and rear sus and tires. We'll set the ride height via the shock mounts. Then haul the roller frame down for a optical alignment check, before we make the final welds.

Since we are working on two frames at the same time, I'm considering to fab a Fixture to secure the front hubs parallel and at the selected height. Prob something simple like 3/4 plywood base and uprights with some bracing. something to hold the hubs in place while we finish up some welds and do the various measurements to square to hubs etc to the frame. You know the importance of the front end sus placement.

We've measured and re-measured the '57 frame and it is amazingly "Square" for a old '57, esp since it was a Police Car. She still has the original black sides and white top paint job. Mostly gone and faded, but very cool. Anyways the frame measures within a 1/16 Cross triangulated in every place we have checked. Yes, We did install two vertical pins at the peak of the rear kick up for the fixed reference point.

As far as the Rear, the Bat Wing mounts / cross member is in place, square and plumb. Once the front hubs are aligned we'll align the rear hubs and screw the rear control arm brackets in place. We'e not going to weld them in place until after the optical check.


IRS Diffy

I did consider hunting down a Dana 44 Diffy core. But this '37 Chevy build is so different in most regards I decided to mate the C4 IRS to the Dutchman's 9 inch IRS Diffy. The Diffy case is wider, so each half shaft will require ~1.030 shortening. I chose 35 spline alloy axles and the the larger 1350 Yoke. The lower Camber control arms will require a lower Bird Cage, that's time consuming but not the difficult. We have all the drawings, so Steve should be able to design the cage pretty easily, We will be adhering to the late lower control arm length. Another reason for the 9 inch IRS Diffy is the ease of installing a a different 3rd member assembly. Plus 9 inch cases are much simpler to assemble and wider parts selection.

The Toe control assembly in the C4 IRS has always be a Thorn in my side. The Pivot point on the rear of the Dana 44 has baffled me for over a decade. We'll use the spindle mount for the inter pivot. The outer will be an interesting challenge. I'm very interested to see what happens when the inner pivot point is moved closed to the inner u-joint C/L. Anyone ???

I know Todd (@ Dutchman's) pretty well and He's always been been fair and honest in all regards. So I trust his knowledge and technical advice, re his 9 inch IRS Diffy. But, I'm still uncertain as to which "Traction Control" to utilize with the Corvette C4 IRS. Currently I'm leaning towards the Truetrac. The Wavetrak is another nice device, esp with the life time warranty. I'm deliberately don't desire a clutched device nor another locker for such a light this weight car. Do you have any experience with the Truetrak or Wavetrak ???

So, there's the plan,, frames first...

Michael

[chevynut]

I'm thinking stick with an inch for tire compression for the '57 HT.. Your Thoughts ???

I already told you my thoughts :-)....I think an inch is too much. You could get anal about it :-D and calculate the size of the contact patch using the corner weight and pressure of the tire. Then all you have to do is figure out what radius gives you that contact patch area. :razz:


Don'y faint, but We are going to bolt the engine cradle in place initially. Once that done we will flip the frame over and finish anything on the bottom of the frame. Then the plan is to re-install the front and rear sus and tires. We'll set the ride height via the shock mounts. Then haul the roller frame down for a optical alignment check, before we make the final welds.

And I thought I was anal. :-D :-D Are you going to re-check after welding? things WILL want to move around a little....at least a few thousandths ;)


We've measured and re-measured the '57 frame and it is amazingly "Square" for a old '57, esp since it was a Police Car. She still has the original black sides and white top paint job. Mostly gone and faded, but very cool. Anyways the frame measures within a 1/16 Cross triangulated in every place we have checked.

You're lucky. I've seen these frames off quite a bit in all the years I've been doing it. Our jig is square so once we cut the front end off the frame we can correct just about anything. The squareness of the original frame really doesn't matter to us.



We will be adhering to the late lower control arm length. Another reason for the 9 inch IRS Diffy is the ease of installing a a different 3rd member assembly. Plus 9 inch cases are much simpler to assemble and wider parts selection.

All C4 lower camber arms are the same length. I'm curious that since you're going through all the trouble of narrowing halfshafts for the differential, why wouldn't you narrow the whole rearend? I made mine 60" wide at the wheel mounting surfaces. When you shorten the halfshafts and not the strut rods you're going to affect the geometry, but I haven't thought about what it does. First impression is that it should increase camber gain. I heard that they lowered the inboard strut rod mount on the late C4 to decrease camber gain.

Yes I hear the 9" rears are easy to work on compared to GM. How much is the whole differential with case, carrier, and gears? I always wondered what a "birdcage" was. ;-)


The Toe control assembly in the C4 IRS has always be a Thorn in my side. The Pivot point on the rear of the Dana 44 has baffled me for over a decade. We'll use the spindle mount for the inter pivot. The outer will be an interesting challenge. I'm very interested to see what happens when the inner pivot point is moved closed to the inner u-joint C/L. Anyone ???

I guess I'm not understanding why the toe rod is such a problem. It's about the same length as the halfshaft stock, so it doesn't affect toe much as it moves. What the "spindle mount" that you're referring to on the inboard pivot? Once you cut the halfshaft down, you will affect it if the toe rod is left the stock length. Seems like you need to shorten it and move the inner pivot outboard. Why is the outer connection a challenge? Aren't you just using the knuckle arm?


Do you have any experience with the Truetrak or Wavetrak ???

I don't know anything about them. :)

I'd be interested in seeing your progress once you get the parts.

[oceangoer]

Laz,

Tires, well We'll mount a few and measure the results.

Frame, oh yes will check after welding. But My TIG isn't up to the Pro level. So at that juncture is off to a friends home shop. He's a Profession
fabricator now with his shop a home. And has several frame tables. Yes, I'm a bit finicky re the frame, back bone on the Car


Diffy, lower control arms same length. The 9 inch IRS Diffy case is wider, hence the narrowing of the half shafts to maintain the original width

[chevynut]

The 9 inch IRS Diffy case is wider, hence the narrowing of the half shafts to maintain the original width

I understand that, but don't understand why you're going through all that work to maintain a 63 1/4" axle width:confused:. Wouldn't it make more sense since you're building a frame from scratch, and you're cutting the halfshafts and making new toe rods, to go ahead and narrow the axle? I sure would. ;)