Comparing tri5 to C4 front suspensions

[chevynut]

I thought I'd bring the discussion about spindles, a-arms, instant centers, etc. into this thread so it doesn't keep the other one off-topic. I wanted to get some actual data on the C4, tri5, and modified tri5 suspension dimensions to analyze.

I just did a quick measurement of suspension parts for both the stock tri5 suspension and both the early and late C4. The measurements were with a tape measure and they're probably accurate to about 1/8" or better.

.................................................. ..Tri5 ..................Early C4 ...................Late C4 ...............Tri5, 1" taller balljoint
Spindle height (balljoint centers) .... 9.75.................. 11.81....................... 13.31................. 10.75
a-arm pivot centers (vertically) ....... 10 ....................10.38 .........................11.13 ....................10
Upper a-arm length (pivot to bj) ..... 11 ....................8.25 ..............................8 ......................11
Lower a-arm length (pivot to bj) .....14.5 .................13.25 ...........................15 .....................14.5

Tri5:
Notice that on the stock tri5 suspension the spindle is shorter than the a-arm pivot centers by 1/4". This results in an instant center outside of the frame, about 450" outside per a quick CAD drawing I did, assuming the lower a-arm is level (balljoint center same height as a-arm shaft centerline). The spindle is taller than I thought it was due to the lower balljoint being below the spindle with the stud pointing upward. The net result is that there is positive camber gain as the suspension is compressed, because the upper balljoint moves outboard while the lower one moves inboard. Positive camber (top of tire outboard of the bottom of the tire) is bad from a performance point of view, as the tire wants to roll under the wheel.

Early C4 (84-87):
The early C4 spindle is significantly taller than the tri5 spindle (2.06"), and 1.43" taller than the a-arm pivot points. This configuration puts the instant center on the opposite side of the car centerline. My quick CAD drawing shows it to be about 48.5" from the upper a-arm pivot inboard (horizontally) to the instant center. Again, I assume the lower a-arm is level. This configuration gives negative camber gain as the suspension is compressed, since the upper balljoint instantly moves inboard and the upper a-arm is shorter than the lower one. Negative camber tilts the tire into the turn, improving handling.

Late C4 (88-96)
Again the spindle is taller than the early C4 by 1.5" and 3.56" taller than the stock tri5 spindle, but the upper a-arm pivot also moves upward .75" from the early C4. This provides even more angle to the upper a-arm, and more camber gain on suspension compression. The lower a-arm is longer, reducing the inboard movement of the lower balljoint, and the upper a-arm is slightly shorter, increasing the inboard movement of the upper balljoint. The instant center is about 34" inboard of the upper a-arm pivot, horizontally.

I didn't do any dynamic analysis, only static and assumed the suspension was at ride height with the lower a-arms level in all cases. That' means the a-arm pivots and the centers of the balljoints are at the same height.

Now, let's look at the 1" taller upper balljoint with the stock suspension. The a-arms are the same length as stock. While the taller balljoint does move the instant center to the opposite side of the car as the stock suspension, it's about 146" from the upper a-arm pivot. The net of this is that it does give some negative camber gain, but not nearly as much as even the early C4 suspension. The upper a-arm is relatively long, which increased the arc the balljoint travels, decreasing the inward movement after it goes level. Also, the lower a-arm is relatively short in comparison, being only 32% longer than the upper one. The early C4 is 61% and the late is 88% longer.

So my conclusion is that while a 1" taller balljoint helps correct the huge problem with the positive camber gain of the tri5 suspension, it isn't that much of an improvement from a performance point of view in improving negative camber gain.


EDIT- For updated numbers please see this thread

http://www.trifivechevys.com/showthread.php/4425-Suspension-geometry-analysis

[chevynut]

Here's some interesting diagrams...

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

[chevynut]

And we haven't even talked about the effect of the anti-dive geometry, steering axis inclination, or scrub radius. Those parameters can't be duplicated with a stock tri5 frame and aftermarket parts.

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



Stock tri5 SAI is 3.5-4.5 degrees. C4 SAI is 8.744 degrees. Scrub radius depends on wheel offset and tire diameter.


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

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

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

So how does Rick's C3 solution compare?

[Rick_L]

Good summary of the suspensions.

Note that the stock 55-57 suspension has some anti-dive also. I've never measured how much, notice that you don't have a number on C4 either.

My C3 Corvette spindle conversion has similar numbers to Rocky's extended ball joint version, except that the upper control arm is shortened by 3/4" or so, and the SAI is 7 degrees instead of 3.5 degrees, improving the scrub radius. My biggest problem is the lowering from shortening the springs.

[chevynut]

The C4 has a lot of anti-dive compared to a tri5 which has some as you say. I can't find the exact numbers anywhere, but upper a-arm shaft is sitting at about 11-12 degrees as I recall, per my measurements. Here's something i found on the net:

1984 AntiSquat 51 % AntiDive 46 %
1985 AntiSquat 51 % AntiDive 46 %
1986 AntiSquat 62 % AntiDive 46 %
1987 AntiSquat 62 % AntiDive 46 %
1988 AntiSquat 62 % AntiDive 46 %
No data from later years.



I'm not sure how this all factors into handling, but we do know that the C4 suspension is a major improvement over the stock tri5 suspension. I don't know how much anti-dive a C5-6 has in comparison. Here's a pic that shows the anti-dive of the C4 suspension pretty clearly.

http://www.trifivechevys.com/attachment.php?attachmentid=5193&stc=1

[Rick_L]

Stock55-57 probably has 1/3 to 1/2 that.

What's not clear is how much anti-dive is too much. Maybe I can find that somewhere.

[JT56]

Nice diagrams Cnut

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

Cnut you see mr Hinkles C4 chassis 55 nomad build on FB? Looks pretty trick so far. Similar color as yours with silver frame.

[chevynut]

Rocky, who the heck is Mr. Hinkles???? :D Is he related to Mr. Hanky?

Got a link to that FB page?

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

Its in the chevynomad group.

https://m.facebook.com/photo.php?fbid=10205509555885129&id=1438481515&set=gm.1498223683810204&source=48&ref=bookmarks

[chevynut]

I took a level out and checked a stock frame, and I get 8 degrees for the upper a-arm tilt (anti-dive). I thought it was a lot less than that.

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

Cnut I'm confused. The trifive lower ball joint loads from the top above the spindle top and bottom same?

[chevynut]

Cnut I'm confused. The trifive lower ball joint loads from the top above the spindle top and bottom same?

Yes, the studs both point downward so the balls are actually above their respective connection points. In mt measurement I assumed both studs were the same length so I just measured the height of the spindle from the top of the upper hole to the top of the lower hole. On the C4 suspension, and most other modern suspensions, the studs point TOWARD each other, effectively increasing the spindle height. The top balljoint is the same but the bottom one comes in from below the spindle and the nut is on top.

You can see the difference here.

http://i43.photobucket.com/albums/e385/55B210/00000002.jpg?t=1272668848

http://nebula.wsimg.com/7fd4f2c39ff550f704691d1ba0946f62?AccessKeyId=1F0AB 926F4CF5A03C38E&disposition=0&alloworigin=1

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

Using data points measured on my nomad 99% weight on wheels I get the following.
For record car has 1/2 inch taller than stock upper ball joints and adjustable upper arms. Dropped approx 2 inches with drop springs. My alignment is roughly set at -1 degree camber. My cad model shows i get about 2 degrees of negative camber with 2 inch of vertical travel. The video also clearly shows that the suspension is creating negative camber has it moves or compresses.

http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_121.jpg
http://vid282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/trim.A35006DA-C596-47CC-A534-01D3157B1360.mp4

[chevynut]

The 1/2" taller balljoints and dropped springs put the upper a-arm such that the balljoint end is higher than the inboard end, so you would get camber gain on compression. But the lower a-arm is not level now, and you will get inboard movement of the lower balljoint and spindle as the suspension moves. To me, that means your tire contact patch is scrubbing in and out some as you go down the road. It's definitely not optimal.

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

Not so. All my measurements agree with yours except I use the pivot point of the ball joints which gives me a center to center spindle height or distance of 11.75. My adjustable upper arm dialed in to -1 degree camber gives a length of approximately 10 inches. This result in negative camber gain in compression. Yes the tire does scrub in some at the bottom. The roll center using your diagrams shows to be about .2 inches off the ground. It may not be optimal but its pretty darn good compared to a stock trifive.

my data points
http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_122.jpg

[chevynut]

Not sure how you're getting 11.75" for the height of the spindle. If your balljoints are 1/2" taller, seems to me like you should be getting 10.25" for effective spindle height. That is unless the balljoint lengths are different.

I can assemble a pair of stock front a-arms and spindle and measure.

I am not understanding what argument you're trying to make here. Yes, the increased length balljoint and lowering helps quite a bit, and moves the instant center to the opposite side of the car.

And lower a-arms are supposed to be level at ride height for a number of reasons, one of which is tire scrub, I believe. When they point like you show, they move the instant center toward the ground. That lowers the roll center AWAY from the CG. I don't think that's a good thing. ;)

Also, where is the optimum point for a roll center? I don't think it's the ground.

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

You said it has postive camber in compression . I say it has negative base on my cad model and video thats my point. Same thing you stated above that the c4 had and the trifive doesn't I say you are mistaken with my setup as it sits it excerts negative camber gain in compression. I myself have no idea what the perfect roll center would or should be. Your comparing the c4 so what numbers does it have as a roll center in your setup? I do know using C4 allows you to even dial in camber in the rear as well.

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

Ok I re did my data points after looking at a pair of ball joints. I came up with a spindle length of 10.38 instead of 11.75 and using this info and raisng the bottom pivot up by .625 and lowering the top pivot from 19.75 to 19.25 i still get negative camber gain thru out compression. The roll center moved to .6 below ground.

[Rick_L]

Rocky, negative camber gain is what you want in compression. Think about it. And I don't think Cnut is disagreeing with that part.

Cnut, have you put some numbers to tire scrub? I don't think that's a relative issue, but will admit that I haven't calculated any numbers.

[chevynut]

You said it has postive camber in compression .

No I did not say that. This is what I said:

"So my conclusion is that while a 1" taller balljoint helps correct the huge problem with the positive camber gain of the tri5 suspension,"



I say it has negative base on my cad model and video thats my point. Same thing you stated above that the c4 had and the trifive doesn't I say you are mistaken with my setup as it sits it excerts negative camber gain in compression.

I agree with you, the taller balljoint fixes the inherent problem with the stock tri5 suspension. That's what I said. However, it doesn't give as much camber gain as either vintage C4 suspension. Now the question is how much camber gain is too much? GM says the 90's C4 isn't too much. ;)


I myself have no idea what the perfect roll center would or should be. Your comparing the c4 so what numbers does it have as a roll center in your setup? I do know using C4 allows you to even dial in camber in the rear as well.

I haven't looked into that but I do know that the shorter the instant center lever arm is the higher the roll center (with a level lower a-arm). And I do know that a non-level lower a-arm (pointing up and outboard) lowers the roll center. And the roll center moves upward toward the CG, the roll stiffness increases and I think that's a good thing. As the roll center drops, the car tends to roll more on turns. That's not good for handling.

For this reason I think dropped spindles are a lot better way to go than lowering springs.

[chevynut]

The other thing that a taller balljoint does is decrease the SAI, I believe. That increases scrub radius.

So while the taller balljoint you're using does fix the positive camber gain of the stock suspension, I think it decreases the SAI a bit, which increases scrub radius. Also, you can't use stock length a-arms since they would be too short, correct? I believe your lowering springs cause the lower a-arm to be non-level, which causes tire scrub as the suspension moves, and moves the roll center downward, away from the CG. This hurts handling.

The latter is illustrated in this diagram I posted above:

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

So If I was going to try to fix the stock supension, I would consider using the taller balljoint, a tubular upper a-arm with increased caster, and of the correct length to allow proper alignment. I'd also use dropped spindles to lower the CG, and a spring that gives a level lower a-arm. I would also add a swaybar. That's about all you can do, and it's still not as good as the C4. ;)

I wonder why nobody has made a spindle and lower a-arm with an inverted balljoint for these cars.

[Rick_L]

I don't know what the formal definition of SAI is, but to me it's the angle between a line drawn through the ball joint and a line perpendicular to the spindle axis. So it's fixed by the spindle's machining dimensions.

I think that some include the camber angle as part of the SAI. But that's a function of alignment and not suspension movement, at least as the starting point.

Perhaps this is all in the twist on words and definitions.

I think I see where you're going but again numbers need to be added to the discussion to understand the relevance.

[chevynut]

I don't know what the formal definition of SAI is, but to me it's the angle between a line drawn through the ball joint and a line perpendicular to the spindle axis. So it's fixed by the spindle's machining dimensions.

I agree. But let's say the holes in the spindle are bored perpendicular to the tapered spindle itself. Then if you increased the length of the balljoints, it would change that angle. Are the holes bored so they line up with each other? If so, the SAI wouldn't change. It's a small mount in any case.


I think I see where you're going but again numbers need to be added to the discussion to understand the relevance.

I'm not really "going" anywhere, just wanted to outline the differences between the various suspensions and analyze what Rocky's changes really did to the geometry. Yes, it improves some things but introduces some other problems, imo.

To me the real questions are how much camber gain is optimal, how much scrub radius is preferred, how much anti-dive is too much, and where should the roll center ideally be. That probably depends on a lot of other stuff.

[Rick_L]

I see your point on the spindle machining. First thought was the holes are in line with a line through the holes, but after thinking about it, maybe not, as I'm pretty sure the flats are parallel to the spindle axis. That would make it logical to machine the holes perpendicular to the flats. I think any difference is slight.

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

The 1/2" taller balljoints and dropped springs put the upper a-arm such that the balljoint end is higher than the inboard end, so you would get camber gain on compression. But the lower a-arm is not level now, and you will get inboard movement of the lower balljoint and spindle as the suspension moves. To me, that means your tire contact patch is scrubbing in and out some as you go down the road. It's definitely not optimal.

I guess you didn't say camber gain here either? The fact is you cannot use drop spindles and fix a trifives handling issues or any other gm car for that matter. Go do some math Cnut. If you drop the CG of the car using drop spindles you have done nothing to correct the trifives positive camber In compression. Adding a taller ball joint to this will reduce positive camber gain but it will still exist. Thats why I've said from the start drop spindles dont cut it throw them in the trash. By using an adjustable upper arm I have effectively shortened it. By using the drop springs I moved the suspension pivots and dynamic travel to produce negative camber in compression. While I have made compromises as you point out I have totally changed the trifives handling characterics. As your diagram shows roll can be controlled by stiffer springs. I'm running 550 plus with sway bars. My cutlass is a proven platform it has the same compromises. Is it optimal compared to a C4? No it isn't but it works and has been proven on a race track many times. Their the good ole boys that figured this trick out. So I'll conclude the trifive suspension will never be made as optimal as the C4 but it darn sure can be optimized to handle pretty darn close to one.

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

Anyone who cares to understand about improving the handling of a classic or muscle car should consult Mark @ SC&C he knows this topic well and is an expert in the topic. If you wish to run C4 he can tell you how to improve it as well. You may also read this link it outlines the issues of the various platforms and how to fix them. As I stated many times the bone stock Abody suspension geometry is worse than a stock trifive. Read it yourself the A-bodys are bad out of the box.
http://www.musclecardiy.com/performance/gm-muscle-car-handling-and-performance-upgrades/

[chevynut]

I guess you didn't say camber gain here either?

What I said was "The 1/2" taller balljoints and dropped springs put the upper a-arm such that the balljoint end is higher than the inboard end, so you would get camber gain on compression". When people talk about "camber gain" with a taller spindle they are referring to the increase in negative camber. That's what I implied, and it's clear if you read the rest of my comments and analysis that's what I meant. I should have explicitly said "negative camber gain", I guess. ;)


The fact is you cannot use drop spindles and fix a trifives handling issues or any other gm car for that matter. Go do some math Cnut.

I don't need to do any math to see that if you lower the car using shorter springs, you change the angle of the lower a-arm such that it's higher at the outboard end than the inboard end. This lowers the roll center and moves it away from the CG. That's not a good thing, as the car will roll more on turns. Even worse, it amplifies the drop in the roll center as the suspension is compressed from ride height. Not to mention the tire scrub issue. A better solution is to lower the CG with dropped spindles that don't negatively impact the suspension geometry and keeps the roll center higher.


If you drop the CG of the car using drop spindles you have done nothing to correct the trifives positive camber In compression. Adding a taller ball joint to this will reduce positive camber gain but it will still exist.

I agree. I don't think I've ever said otherwise. ;)


Thats why I've said from the start drop spindles dont cut it throw them in the trash.

This is where you're wrong. Dropped spindles lower the CG while maintaining proper lower a-arm geometry. The lower a-arm should be level or possibly even slightly low at the outboard end. This keeps the roll center closer to the CG, which reduces roll and improves handling performance.


By using an adjustable upper arm I have effectively shortened it.

What did you shorten? With a 1" taller upper balljoint your upper a-arm has to get slightly longer to maintain proper alignment. With a 9.75" or 10.25" spindle height the a-arm is theoretically exactly the same length. Any taller spindle and your upper a-arm must get longer to maintain alignment.


By using the drop springs I moved the suspension pivots and dynamic travel to produce negative camber in compression. While I have made compromises as you point out I have totally changed the trifives handling characterics.

I have never disputed that what you have done improves the handling over a stock tri5 suspension. That design is 60 years old and has a lot of deficiencies, one big one being the positive camber gain we've been discussing. It was GM's first unequal length a-arm design and history has shown that all things considered it wasn't too bad of a design. But as I've pointed out, you have lowered the roll center which doesn't have to be done if you use dropped spindles. Your car will want to roll more with the 2" lowering springs than with 2" dropped spindles.


As your diagram shows roll can be controlled by stiffer springs.

Stiffer springs are not always a better thing. They WILL reduce ride quality and they can cause the suspension to not follow road irregularities by limiting suspension articulation. IMO (repeating) a much better solution is to use dropped spindles to lower the CG and maintain correct lower a-arm geometry, which keeps the roll center closer to the CG. Use the lightest spring rate you can to hold the car at ride height and use a reasonably sized swaybar. Too stiff of a swaybar can cause oversteer and understeer issues too. It can also result in reduced ride quality and traction as one tire hits a dip or a bump and the other wants to react.


So I'll conclude the trifive suspension will never be made as optimal as the C4 but it darn sure can be optimized to handle pretty darn close to one.

You once said you could get C4 suspension geometry with bolt-on upgrades. ;) I think this analysis shows that you can't and I'm glad to see you're coming around. It also shows that lowering a car by cutting the springs causes unwanted changes to the roll center. It does lower the CG and make the spring stiffer which could help handling but the negative effect is more roll. It also reduces suspension travel. It's a compromise I personally wouldn't make because you don't have to. :)

My C4 conversion lowers the front suspension by 3" from a stock tri5. I don't change any of the suspension geometry that GM designed over 3 decades after designing the tri5 suspension. The a-arm angles are left as intended and the anti-dive isn't changed. You can spend a ton of money on new balljoints, new a-arms, a steering box, a swaybar, dropped spindles, disc brakes, and all the other bolt-on stuff and still not duplicate the handling of a C4 front suspension. Lots of my customers have done this and come to the realization that a C4 front clip is the best and most cost-effective way to get what they want. And it's lighter too. :) An entire C4 front suspension with steering rack, swaybar, and brakes can be had for under $1000.

Thanks for the discussion and debate. I'm not saying that what you've done is necessarily a bad thing, and it will improve the handling of a 60 year old design. I'm just saying there are better ways to do it that don't make the compromises you've made.

Here's a good article on roll center:

http://www.thecartech.com/subjects/auto_eng2/Roll_Center.htm

What is a Roll Center?
A “roll center” (RC) is a theoretical point around which the chassis rolls, and is determined by the design of the suspension. Front and rear suspensions have different roll centers.

A “roll axis” is an imaginary line between the front and rear roll centers.

The amount that a chassis rolls in a corner depends on the position of the roll axis relative to the car’s center-of-gravity (CG). The closer the roll axis is to the center of gravity, the less the chassis will roll in a corner. Chassis rolling at one end of the car or the other gives more grip to that end of the car.

Roll center is one of the most under-utilized adjustments on a car, but one of the most powerful. This is because roll center has an immediate effect on a car’s handling, whereas anti roll bars, shocks and springs require the car to roll before they produce an effect.

For the purpose of this article, I have borrowed explanations from a variety of sources, and I will try to paint a clear picture of how roll center works.

Roll Center Basics
Here are some basic facts about roll center (RC) and center-of-gravity (CG).

* Roll center (RC) is the point around which the car rolls
* Each end of the car (front and rear) has its own roll center
* Center-of-gravity (CG) is where all cornering force is directed
* RC and CG are (ideally) in the middle (left-right middle) of the car
* RC is vertically below the CG in cars
* Rolling produces more grip



Effects of Front Roll Center Adjustment
Front roll center has most effect on on-throttle steering during mid-corner and corner exit.

LOWER front roll center

* More on-throttle steering
* Car is less responsive

* Better on smooth, high grip tracks with long fast corners


HIGHER front roll center
* Less on-throttle steering
* Car is more responsive

* Use in high grip conditions to avoid traction rolling
* Use on tracks with quick direction changes (chicanes)

[chevynut]

I wonder if there's a good bolt-on solution lurking here. :)

Perhaps one could get a lower a-arm that would accept a "pull-type" modern lower balljoint with the stud pointing up. What if a guy obtained a spindle (steering knuckle) and inverted the taper in the lower hole somehow, or used a different or custom spindle configured that way? When you bolt this together, you have now essentially raised the spindle, thus lowering the car and no longer need dropped spindles. I'm not sure how much it would lower it, but it seems like it would be significant. It would also significantly lengthen the spindle, possibly on the order of 3". This would also fix the positive camber issue with the stock geometry, but wouldn't address SAI or scrub radius at all.

Hmmmmm.

[Rick_L]

Well it's "bolt on" if you have some CAD/CAM software, the ability to use it, a CNC mill and lathe, and the ability to use them. ;)

Rocky is wrong on the drop spindles. Lowering the CG helps with no other changes, and it still helps when other improvements are made. There's no reason you couldn't use a taller spindle (or extended ball joint) with a dropped configuration.

On the other hand here's a reason that the car lowered with shorter springs isn't so bad: You're still using the original control arm length and pivots; you're just using a different starting spot on the travel.

[chevynut]

On the other hand here's a reason that the car lowered with shorter springs isn't so bad: You're still using the original control arm length and pivots; you're just using a different starting spot on the travel.

Yes it's a cheap way to get a lower CG, but it's not nearly as good of a solution as dropped spindles. If you're going with disc brakes anyhow, it's more cost-effective and provides better geometry if you go with dropped spindles and disc brakes than a stock spindle and disc brakes, imo. It doesn't increase the roll and roll is easier to manage. Dropped spindles also don't limit suspension travel. Just a better overall solution, imo.

[chevynut]

Well it's "bolt on" if you have some CAD/CAM software, the ability to use it, a CNC mill and lathe, and the ability to use them. ;)


I wouldn't be surprised if you couldn't find an OEM spindle that would work if you searched enough. Then you could use those adjustable upper control arms and a lower control arm that will accept the new style balljoint....or modify an aftermarket one. It doesn't seem like it would be that hard to do. I wonder how a C4 spindle would match up. :)

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

How about we start another topic called throw darts at Rocky so we can keep this thread on subject. If your intent was to actually compare my Setup and stock trifive setup against the c4 then please do so. Stop with the suspension theroy horse poop and plot the data. Can you? If not I will be glad to. I have a 3d model of the c4. It shows the lower arm and top arm both pointing down almost 10 degrees. When you start the suspension travel it actually goes positive in camber. Using a 26 inch tire and zero offset appears to put the roll center about 6 inches above the ground. Even the great C4 can be better optimized maybe you should study it more to improve your product. A car built to handle is going to reduce suspension travel need because it will be inherently stiffer by nature. The loss of suspension travel is a mute point.

Rick yes drop spindles help but dont fix. My solution fixes the problems.

the c4 model is at this link for reference.


http://www.3dcontentcentral.com/parts/download-Part.aspx?id=443356&catalogid=171

[Rick_L]

If I go to the trouble of registering and logging on to that site, what do I get when I download? I.e., a .pdf file, a .dwg or .dxf file, or a 3D cad file? Or a suspension analysis format? What s/w if any will I need to open/view it?

Do you have the stock 55-57 or your modified version in that same format? Can you post those?

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

Your choice Rick it has multipule 2d and 3d formats. Lots of other 3d data on site pretty cool stuff.

[chevynut]

Nobody's "throwing darts" at you Rocky, so stop with the defensiveness. Sheesh! You're as bad as the other guy here who whines when you challenge or correct him. LOL! :) We're just having a technical discussion about suspension geometry including yours. :eek: I showed that your solution is sub-optimal, and that dropped spindles with the longer balljoint is a better solution. I also explained why that's the case. If you don't believe in "suspension theory" and geometry, than you're no different than the guy who said he doesn't believe in the laws of physics and you can't discuss anything with a person like that.

I showed that your setup is better than the stock tri5 setup in terms of negative camber gain. In the other thread, there was also discussion about spindle height and camber gain and how the C4 suspension compares to the Tri5 suspension, so I posted the data on both vintages of C4 suspensions, and showed why they're better. I brought all the data here to discuss the differences. If that offends you, I'm sorry.

That "3D model" you refer to is a bit bogus IMO. At least I don't believe it shows the suspension at ride height, and I don't see where it claims to. It might show the lengths of the a-arms and anti-dive angles correctly. The guy took the measurements off of his car and who knows how accurate it is. I believe at ride height the steering tie rods are supposed to be level, or nearly so, and at that configuration the lower a-arms are level on top. That's how I set them up in my jig and everything works out the way it's supposed to. I also said that it's possible that the lower a-arm would be in a slightly better position if it was pointing slightly DOWN at the outboard end at ride height. Pointing the other way is bad as far as roll center.

I have several of each suspension here...in my shop...and I've mounted them to frames dozens of times. The upper a-arm definitely points DOWN toward the center of the car and it's visually obvious on the late suspension. You can also see that in the c4 dimensions I posted, if you believe them. Just compare the spindle height with the a-arm pivot height. If you don't believe the numbers, I guess that's your choice. They came off of ACTUAL parts.

If the upper a-arm is pointing downward and inboard, it WILL move the top of the spindle inboard as it moves upward. That's common sense with unequal length a-arms and the lower one level. I don't need any more "data" to prove that.

By the way, the upper a-arm mounting height I posted for the C4 suspensions is at the CENTER of the upper a-arm shaft. Since it angles downward at around 12 degrees, that's significant when you're looking at the suspension from the front.

You seem to have a mental block about the dropped spindles. They FIX the flaw in your solution, which is the angle of the lower a-arm due to your cut springs. That angle causes the roll center to be lower than it needs to be, causing more body roll than you'd get with a dropped spindle and extended upper balljoint. I don't see why you keep denying that FACT. Dropped spindles AND a longer upper balljoint is superior to your solution. If you think otherwise, please explain why.

[chevynut]

Don't know what to tell you, Rocky. These dimensions say the upper a-arms point downward toward the center of the car with the lower a-arm level. Do you disagree that the lower a-arm is level at ride height?

.................................................. ....................Early C4 ...................Late C4
Spindle height (balljoint centers) ....................... 12.25....................... 13.75
a-arm pivot centers (vertically) ............................10.5 .........................11.25

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

Cnut I don't really know I figured you would. All drawings and model I have found show it pointing down see link.http://mobile.web-cars.com/carvette/1984-corvette-3.php I cut threw the suspension at its center so its pretty close if model is close. The guy stated he measured a c4 weight on wheels to develope the model.

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

This is the discussion that generated the model appears they point down from everything I found. They also discuss putting longer howe ball joints on a C4 to improve some of its flaws.
http://www.corvetteforum.com/forums/autocrossing-and-roadracing/1905620-c4-frame-and-suspension-cad-files-2.html

[chevynut]

FWIW, here's some C5 dimensions I got off some parts I have:

.................................................. .....C5
Spindle height (balljoint centers) ......12.75
a-arm pivot centers (vertically) ........ unk (anyone know??)
Upper a-arm length (pivot to bj) ..... 8.625
Lower a-arm length (pivot to bj) ..... 16

I will re-check my C4 measurements to make sure I didn't screw up somewhere especially the spindle height and pivot dimensions. The 2"+ difference I posted seems high to me, based on my visual observations.

This picture made me start wondering about my dimensions. Note that the center of the a-arm shaft is lower than the front of the shaft shown here. This is the early C4 and I don't know where the drawing came from. But it doesn't match what my measurements suggest. Also note that the steering tie rods are angled downward slightly as are the lower a-arms. This is what I eluded to about having the lower a-arm slightly down like this at ride height. Clearly the 3D cad model was different than this one.

http://mobile.web-cars.com/images/vette_m_img/1984-Corvette-front-view-outline-2_a.jpg

But I'm off to SEMA right now...will check when I get back.

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

The models indicates that the ball joint to ball joint center height is 13.866 center of ball to center of ball.

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

If I go to the trouble of registering and logging on to that site, what do I get when I download? I.e., a .pdf file, a .dwg or .dxf file, or a 3D cad file? Or a suspension analysis format? What s/w if any will I need to open/view it?




I found a C3 suspension model on the site that might interest you.

[chevynut]

Here's another drawing from the side '84 C4:

http://mobile.web-cars.com/images/vette_m_img/1984-Corvette-side-view-outline-A_a.jpg

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

As for drop spindles I'll stick to what I said above as to why they aren't a good option if your goal is to improve handling. Here is Marks reasons why not to use them it makes perfect sense to me. Again every one should read the the info I linked it is directly from the gurus mouth.
Quote"
So, what about 2-inch-drop spindles that aren’t taller than stock? Do they move the critical pickup points to improve the geometry? No. Do they do anything to improve the steering geometry? No. Do they cause more wheel/tire clearance issues? Yes. Do they make it harder to use performance-bred lowering springs and still have a usable ride height? Yes. Well, three strikes and you’re out…and they got four. Make it five, because you already have stock spindles, and you have to pay for these 2-inch-drop spindles. Again, do the homework first, and know what you’re getting before laying out your hard-earned money. Unquote"

[Rick_L]

So, what about 2-inch-drop spindles that aren’t taller than stock?

Well, what about 2" drop spindles that are????

I don't buy all the "other" reasons.

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

Well it's "bolt on" if you have some CAD/CAM software, the ability to use it, a CNC mill and lathe, and the ability to use them. ;)

Rocky is wrong on the drop spindles. Lowering the CG helps with no other changes, and it still helps when other improvements are made. There's no reason you couldn't use a taller spindle (or extended ball joint) with a dropped configuration.

On the other hand here's a reason that the car lowered with shorter springs isn't so bad: You're still using the original control arm length and pivots; you're just using a different starting spot on the travel.
Lol Rick for the same reason you don't buyem yet you do. Read your last sentence. You nailed it so you must get it? Bingo we have a winner!!!

[Rick_L]

Rocky all I found was a C3 frame, no suspension. Do you have a link or more info?

I did register and see that the site is associated with Dassault Systems, which is a good thing. Hopefully I can download the file as an eDrawing which is their software. You can't create or edit an eDrawing, but it is very good for viewing.

[Rick_L]

Lol Rick for the same reason you don't buyem yet you do. Read your last sentence. You nailed it so you must get it?

My comment that you quoted was about non drop spindles.

My later comments were about drop spindles. I definitely think they would work better.

As pointed out in another post, there are no commercially sold C3 Corvette dropped spindles. However there are 58-?? Impala drop spindles but they won't wear the C3 brakes, at least directly. So I am stuck with the stock drop C3 spindles I have put on the car. We'll see how they work out.

[Rick_L]

Tried to download eDrawings. "This program requires Windows 7 or Windows 8.1" I have the dreaded Windows 8. Will have to do some more work.

I had the same problem with Dassault Systems "Draftsight", except that Draftsight won't even use 8.1. I have some work to do.

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

Rick here is the link to the C3 model there is also other stuff as well rear end tube frame etc. The model states improved c3 front suspension.
http://www.3dcontentcentral.com/download-model.aspx?catalogid=171&id=401166


I was aware that your statement was about non drop spindles but it defines the reason why to use drop springs instead of drop spindles. I am also confused reading back you stated C3 spindles are not drop spindles? We can discuss your c3 design but Cnut did not invite your setup into the thread lol and If we go off topic he might delete it lol.

[Rick_L]

So I can't participate with a suspension setup similar to yours?

Or is it because I agree with Cnut? He won't delete my stuff if I agree with him.

I think you're a bit touchy. No one is trying to bash you, you're bringing it on yourself.

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

deleted off topic

[Rick_L]

Rocky you seem to only read the parts of the replies that you want to read and neglect the rest.

FYI my car WILL be lowered with short springs.

Please post your diagrams, it will be much easier to discuss things.

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

deleted off topic

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

Rick this is a sketch I pasted above of my measurements which were corrected after this but you can take you numbers and feed them in and do the same thing in any 2 d cad. My cad model is just a 2d not any more clear than this for sake of conversation. I use the arm arc lengths and rotate them to a given distance and put a point were they cross and you have the spindle axis and its change thru the range of motion.

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

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

Rocky you seem to only read the parts of the replies that you want to read and neglect the rest.

FYI my car WILL be lowered with short springs.

Please post your diagrams, it will be much easier to discuss things.

So now I've stopped throwing darts at Cnut and I'll start with you Rick LOL.

Did you not say this above?

"So I am stuck with the stock drop C3 spindles"


Sorry if I miss read into that lol. But maybe you can see why I went a bit off course.


Also not reading your statement about drop spindles "that are". I assume your saying longer than stock. Who makes drop spindles that are longer than stock that will fit stock trifive arms? If you are referring to chassis works that also come with matching arms and spindles setup for coil overs the price point of such animals would push me and most poor folks to use Cnuts C4 solution and product. So I really don't see a point of bringing them into this conversation.

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

Ok here is a mod for you. What if you notched the bottom of the frame weld in bath tubs and move the lower arm mounting points up to level. Mine need to go up 1.5. Not sure exactly the pros and cons of doing that as far as impacting something or how it will effect travel or ride height just a thought in my head. It would move the roll center up to about 3 inches from the ground per my cad model. 3.5 higher than it is now.
Rocky

[Rick_L]

I'm done with this. You don't answer questions and you just continue with the same old stuff.

I'd rather have a clip or aftermarket frame than make the mod you suggest. It just doesn't make any sense to do.

[hutchenc]

Rocky, I have a suggestion (not a dart) for you.

Instead of arguing that your method is better (without any actual data to prove it), prove that your method is better than running a set of drop spindles and coil-overs with non-adjustable aftermarket a-arms. Go put your car on an alignment machine and measure the camber at different ride heights like this fellow did: http://www.pozziracing.com/second_gen_camaro_tall_bal.htm

After you've received some actual data, post it.

Alternatively, go race your tri-five against another tri-five with modifications like mine has (which are pretty typical bolt-ons) and compare times.

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

Hutch sorry I hi jacked your other thread that apparently spun this one out. I'm really tired of trying to lead you old horses to the water hole you just dont drink. I tried to help you make a simple cheap change to your already finished car that will make a very dramatic change in your stock suspension. If you had made a call to Mark @ SC&C as I have suggested ever time this comes up he would have made you understand. It is to late you have thrown in towel and went C4. He can even help you improve it. Give him a call and learn something. None of us arm chair suspension designers really know anything about the topic. He does he not only help develope this little mod I have for many platforms including C4 he has been involved in the design and developement of many of the after market protouring hardware for the pro touring world.

With these data points in sketch below corrected above at 2inch of compression you would get approx 1.44 degrees of negative camber gain in bump. You already have 1 degree of negative camber in the alignment to start. I haven't seen any C4 numbers mentioned here? Altough this little mod does not give you the optimal roll center it does however move it from left field and puts it in the center of the car. Will this cheap little mod be better than C4 no it want. Infact with C4 if you want to get real series and you start moding it you will quicky leave the cheap little mod I advocate in the dirt. But If you put this little cheap mod on a race track against a stockish c4 setup its going to hang with it or beat it all other things equal the driver will make the difference here. I believe i did post real numbers on an ax course with this mod competing against the Mary Posi types (pros) to support that statement. She has won multiple national championships on leaf springs imagine that. I chased art morison c4 chassis nomad around a 60 second average course he bested me by I second. He was also packing north of 700 hp and a 6 speed manual. If your hearts set on front clips on a tri five why not a IROC Z front clip. Fact is it had same or better skid pad numbers than a c4 of that year. I owned one it was my first taste of a car build to handle. My current A body would have better numbers than it. I dont thing the Iroc had optimal suspension either. Another fact the frame and suspension of a trifive is better in stock form than the A body. If you need proof of that statement call Mark. So I'll say it again this is the best bang for the buck out there. Your list of trifive mods with out this mod is what Mark means about putting lip stick on a pig. You handy cap all the other mods if you dont correct the suspension which this does. Night and day not just a little improvement as everyone in the trifive world old guard seem to think except the ones who have actually done it imagine that. Good luck hope the C4 works out. It will be interesting to see how it works with a stock trifive rear leaf instead of the vet rear in cnuts chassis kits.



my data points
http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_122.jpg

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

Here is some C4 data may be worth a read apparently it has some pos camber gain issues itself in stock form.
http://www.corvetteforum.com/forums/autocrossing-and-roadracing/1905620-c4-frame-and-suspension-cad-files.html


AND READ THIS LINK ANYONE who wants to know something about this subject matter. You will see real open road race numbers on a real amercian highway and guess what a gbody with this same little mod won the class bested C5/C6 new vets. Mark knows his stuff call him for real knowledge about this cheap little mod or Cnut's full C4 chassis. Laz I will assure you one call to mark explain what your doing and I assure you he can help you improve your baseline C4 design.
Rick I'm done here too. I invited Mark to join in to teach you guys something if he doesn't I don't blame him plenty of google info on him his back ground and what he has designed and implemented into this hobby and race community.

http://www.chevelles.com/forums/showthread.php?t=176176

[hutchenc]

http://replygif.net/i/166.gif

[56Chevy4Dr]

Rocky, I like the idea of bathtubing the lower A-Frame mount supports to improve a more favorable negative camber during suspension compression. You could also reposition the mounts that it is slightly closer to the front bumper benefiting more caster (if you can't get enough desired caster with the adjustable a-frames). As Cnutt suggested, one would think that you could weld up the lower spindle ball joint hole, then re-drill it with an inverted taper to accept the ball joint upside down (assuming that the lower ball joint could be mounted in the lower a frame upside down). That would give you the better lower a frame angle for more negative camber in suspension compression and roll center vs center of mass relationship, effectively decreasing body roll in a turn. This angle could be further adjustable by using an extra tall lower ball joint as discussed earlier with the upper a-frame. I dare say, when welding up the lower spindle ball joint mounting hole, it to be repositioned closer to spindle adjustment adjustment nut for a better Steering Axis Inclination angle to improve scrub radius, if needed.
In the suggested Corvette forums, it was exploited (meaning improvements could be made) that the C4 suspension has innate problems as well.
Why couldn't a sixty-year-old suspension be reengineered to outperform a thirty-year-old C4 suspension? However, after all these suspension angles are reconfigured and adequate sway bars and spring rate installed, I think the dropped axle spindles would be better to lower the car keeping full suspension travel (assuming the car does not bottom out or hit the ground).
This is my very first post in this forum and I have been enlightened quite a bit on suspension and how complex a modification can be.
Thanks.

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

Welcome 56. You should introduce yourself in the welcome section.
Rocky

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

hutch just for the record the C4 nomad spanked me but I did manage to out do the fire truck lol.


http://i282.photobucket.com/albums/kk243/rockytoppers1/IMG_2780.jpg
http://i282.photobucket.com/albums/kk243/rockytoppers1/IMG_2783.jpg

[hutchenc]

Is that your car rocky? If so...get that thing on an autocross track! Very nice! Love the color and the wheels and the stance. Go see what it can do man!

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

Hutch that pic is at a autocross. That is the AM C4 chassis nomad I referred to above. It has a LX454 an 6 speed lurking below. I thank it is from Houston TX area. My grey car is parked 3 cars down the row.

[chevynut]

I did some more accurate measurements on the C4 parts and here they are. The biggest change was due to the length of the balljoints. Previously I estimated where the balljoint centers were for my measurements. Since I disassembled my a-arms I was able to see exactly where the center is. It looks like the center of the balljoint is 1 1/8" above the top of the spindle. I'm going to assume the lower balljoint is the same length, but I have not taken one apart to measure it. Here's the OLD measurements:


.................................................. ..Tri5 ..................Early C4 ...................Late C4 ...............Tri5, 1" taller balljoint
Spindle height (balljoint centers) .... 9.75.................. 12.25....................... 13.75................. 10.75
a-arm pivot centers (vertically) ....... 10 ....................10.5 .........................11.25 ....................10
Upper a-arm length (pivot to bj) ..... 11 ....................8.25 ..............................8 ......................11
Lower a-arm length (pivot to bj) .....14.5 .................13.25 ...........................15 .....................14.5

And here's the new ones. The early C4 spindle is 9 9/16" tall. I added 1 1/8" to each end for the balljoint and did the same for the 11 1/16" tall late C4 spindle. I also re-measured the k-member a little more accurately to get the pivot point dimensions.

.................................................. ..Tri5 ..................Early C4 ...................Late C4 ...............Tri5, 1" taller balljoint
Spindle height (balljoint centers) .... 9.75.................. 11.81....................... 13.31................. 10.75
a-arm pivot centers (vertically) ....... 10 ....................10.38 .........................11.13 ....................10
Upper a-arm length (pivot to bj) ..... 11 ....................8.25 ..............................8 ......................11
Lower a-arm length (pivot to bj) .....14.5 .................13.25 ...........................15 .....................14.5

The net of this is that the upper a-arm balljoints are STILL above the pivot points with the new measurements. The early C4 spindle is 1.43" taller than the pivot points, and the late C4 spindle is 2.18" taller than the pivot points. With the lower a-arm level, the upper a-arm angles down toward the center of the car.

I corrected the numbers in the original post just so someone doesn't use the wrong dimensions, but wanted to preserve them here. ;)

I also took a look at the 3D CAD models that Rocky posted. That stuff is wrong. First of all, the front end is NOT at ride height. Secondly, look at the rearend. He has the halfshafts shown with the outer u-joint forward of the inner one. That is not the configuration of the C4 rear. The u-joints on the inboard side at the diferential yokes are around 1" or more forward of the outer u-joints at the knuckle. Bottom line is those 3D models are BS and I wouldn't trust them. It's possible the lengths are okay for some of the members, but they don't model a suspension in an actual C4 Corvette at ride height.

[chevynut]

That is the AM C4 chassis nomad I referred to above. It has a LX454 an 6 speed lurking below.

AM (Art Morrison) doesn't make a C4 chassis. ;)

[chevynut]

Here is some C4 data may be worth a read apparently it has some pos camber gain issues itself in stock form.
http://www.corvetteforum.com/forums/autocrossing-and-roadracing/1905620-c4-frame-and-suspension-cad-files.html

There's really nothing new in that link, it's a speculation and guessing. The only thing worthwhile was the CAD layout of the front suspension what shows the correct orientation of the upper a-arm. Some guys said it sloped down, which is wrong. And they don't even say which C4 suspension they're talking about, even though they're significantly different from early to late. That thread is about worthless.

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

AM (Art Morrison) doesn't make a C4 chassis. ;)

Sorry I am wrong your right nut case they have a superior suspension to C4 so my bad I gave your turd more credit than is due and I apologize for that. Just trying to help your illusion Lol.

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

Nut case sense you wish to open up this old thread today and Glorify your self once again and continuely try to discredit me by telling the world that I'm off topic and get my panties in a wad and then start a new one. You should of least post factual info and assumptions in the new one before spreading the same false information that you started in this one if your real goal is to inform and learn from. Hell you can't even post your on C4 design of your nomad to compare.
Your cowardly ass can continue to wezel. Every thing you said todate is useless or false. My cards are played. I'm calling show your hand or shut the Phuck up. Your assumptons that a stock trifive lower arms are level from a cartoon service manual is horse poop.That alone discredits ever statement to follow and win your argument against me to further try to dis credit me with your line by line rebutals. So no I must apolize once again but this coward aint about to play in the new same old game and horse poop being spread. You sperts deside for yourself. I already showed you the light and your to dim to see it.

[Classicgary]

well that was special...........

[chevynut]

Well Rocky went on a rant on a couple of threads for some reason that I don't understand. I posted the C4 specs here and he wouldn't take the time to analyze them or much of anything else. He claimed we "armchair engineers" don't know anything about suspension design but I think we proved him wrong. But since Savitche or whatever his name is is who he worships, he can't accept that we might know a little too.

I lost track of this thread somehow and never saw some of the replies so I came back to read them when I was looking for my original measurements.

I did prove that the lower a-arms are just about level, as I said they should be, despite his insistence otherwise. Rocky posted these pictures that misrepresented the truth and apparently still won't acknowledge his error. He did acknowledge that he was wrong about the extended upper balljoint length he was using and it's 0.9" instead of the .5" he was claiming.

I started a new thread where I did a fairly complete analysis of the stock suspension with a few mods, one of which is Rocky's setup, and both the early and late C4 suspensions. I took it there because of the useless rants an garbage on this thread. The end result was that his setup does improve the stock suspension significantly, but with some big tradeoffs. Also, one of my main points was that dropped spindles were better with his tall balljoint than his dropped spring setup. In the end, it depends on what you call "better" . The analysis I did is here:

http://www.trifivechevys.com/showthread.php/4425-Suspension-geometry-analysis

Rocky did apologize for his rant on another thread, but I think he owes me an apology on this one too. When debating, there's no need for personal attacks and I wanted to show the facts from an engineering perspective, not opinions. Some people take debates too personally. ;)

BTW, good to see you here Gary.

[Rick_L]

I'm like you, I too had missed some of the replies in this thread. I wonder what's up with that? It is something that I would have read if it had been on the "new posts" screen when new.

But that's water under the bridge. The more recent thread presents things more clearly and with more facts as opposed to speculation.

[chevynut]

I have no hard feelings toward Rocky and I think he's a good guy. He seems to have gotten frustrated with 3 of us on the other side of the debate. That's why I felt the need to do the complete analysis, and I learned some things doing it. Like I said on the other thread, Rocky's solution is probably a good, cheap way to get a better performing stock suspension if you mostly race the car. I think there are some significant issues with it but the taller balljoint does work and I always agreed it would help. I still think the dropped spindles that Rocky called "junk" are a better overall solution than his, with the taller balljoint and perhaps with a 1" dropped spring to gain some more camber and drop the car a little more.

For some reason, Rocky has avoided responding to the other thread.

[Classicgary]

thanks, ive "been away", building a '28 ford hotrod. I'm back now.
I've got a '57 chevy 2 door sedan to build. !!!

Oh, and in all of the above, there are no specs on using C3 spindles and brakes. A mention, yes, but no numbers.
Anybody have any? I'm going to use the C3 stuff on the '57. It's tried and true for me......
So don't try to talk me out of it, LOL !!

[Rick_L]

Check the other more recent suspension analysis thread. I have C3 spindles and brakes on my car and added that to the analysis thread.

Here's a summary of the specs:
Spindle is 1" taller that stock 55-57, length = 10.75".
SAI is 7 degrees as opposed to 3.5 degrees stock.
Upper control arm length is approximately 3/4" shorter than stock 55-57.

My recollection is that you posted on chevytalk about the C3 spindle when I first considered it, years ago.

The roll center and camber gain with a 2" spring drop and C3 spindles is much better than stock - similar to the 0.9" extended ball joint. Scrub radius is improved.

[chevynut]

Rick, I knew you were using the C3 spindle but I didn't know you were using the upper a-arm too. How do you adapt that to the tri5 frame? Also, I assume the increased SAI takes care of the shorter upper a-arm?

I still think a 2" dropped spring is a mistake and increases tire scrub.....how is it different with the C3 spindle? I calculated that the lower balljoint moves laterally .417" in the next 2" of compression travel. The camber gain offsets some of that, but it's still a lot of scrub.

[Rick_L]

I'm running a tubular upper arm for a 55-57 that's been shortened. The taller spindle and increased SAI requires a shorter arm - should be obvious. I have no idea what a C3 upper arm looks like or where its pivot is located.

I don't think anything is different in tire scrub between stock suspension and a suspension with the C3 spindle. 0.4" seems like a lot based on the geometry, I'll check my layouts.

Edit: my layout shows 0.17" scrub in the first inch of travel when you lower the car 2" with a shorter spring.

[chevynut]

I don't think anything is different in tire scrub between stock suspension and a suspension with the C3 spindle. 0.4" seems like a lot based on the geometry, I'll check my layouts.

Edit: my layout shows 0.17" scrub in the first inch of travel when you lower the car 2" with a shorter spring.

It's really not the spindle, it's the fact that the lower a-arm is angling upward at ride height by 2" at the end, then goes up another 2" at full suspension travel. At least that's what I modeled for a 2" cut spring and got 0.417" of lateral movement of the balljoint. That is somewhat offset by the negative camber gain to get a net of .22" of tire scrub at 2" of compression. That just seemed like a lot to me. A stock suspension has 0.180" of tire scrub so maybe that's not that bad, but the 2" dropped spindle with tall balljoint showed only 0.039".

[Rick_L]

Yes I know. Check your numbers, I stand by mine.

[markm]

Does it make a difference that a 57 has shorter springs, and tires than a 55/56. I remember sales lit. that talked about a newlower stance for 57. It has appeared you discussions have not been year specific.

[chevynut]

The 57 springs are the same as the 55-56. The tires are shorter, as well as the rear spring being mounted higher in the frame at the front leaf spring mount. It makes it about 1/2" lower overall.

[chevynut]

Yes I know. Check your numbers, I stand by mine.

I don't know why you didn't address this in the other thread. :confused:

I just checked my numbers.

I put the datum at the lower a-arm pivot with the arm 14.75" long. Starting with the lower balljoint 2" above the pivot, then raising it 2" you get a horizontal movement of the balljoint inboard of .417". It starts out at 14.614" outboard of the pivot, and ends 14.197" outboard of the pivot. The difference is .417". Do you agree so far?

The change in camber is -1.49 degrees at 2" compression. If the tire is straight up at ride height, then it rotates 1.49 degrees around the lower balljoint". If we use the assumed 225-60-15 tire the balljoint is 7.59" off the ground. So simple trigonometry says the tire contact patch moves .197" outboard with that camber change alone.

The net tire scrub is the difference between the lateral movement of the balljoint and the lateral movement of the contact patch, so you get 0.220" tire scrub.

Check your numbers, I stand by mine. :)

[Classicgary]

yes to the talk on chevytalk a LONG time ago. :)
i did the C3 thing on my '56 way back in the 90's. Drove that car for many many years with that setup.
Funny thing, the guy i sold the car to changed everything thinking "bolt on" stuff from a classic chevy parts place was better
than my "home done" stuff. HaHa joke was on him.
Anyway. i'm going to do the C3 thing on my '57, because i know it works, even though it ain't the latest "trickest" deal in town.
and parts are pretty much everywhere and the whole thing is just about a bolt on, the hardest part being "narrowing" the upper
control arms. But how offen do those need replacing once it's done?
SO, back to my question.
I was just curious as to the numbers. It really doesn't matter, 'cause i know it works FOR MY NEEDS.
And, the way i "narrowed" the upper A arms, was cut it, remove 5/8" (cause the cutting tool takes out 1/8" on each cut),
weld it back together with the bias to the rear of the car. Easy peasy.....

[chevynut]

Gary, go visit the thread on suspension analysis. If the spindle height changes to 10.75" it's pretty close to the 10.65" for the .9" extended balljoint. The additional SAI should help and I think it may even help with camber gain, especially while turning. That's one factor we didn't look at extensively.

[55 Rescue Dog]

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.

[Rick_L]

If the spindle height changes to 10.75" it's pretty close to the 10.65" for the .9" extended balljoint. The additional SAI should help and I think it may even help with camber gain, especially while turning. That's one factor we didn't look at extensively.

Who is we? I published analysis for the C3 conversion and several others. You never commented. I guess you figured it wasn't worth reading since you didn't write it or do the analysis.

[chevynut]

Who is we? I published analysis for the C3 conversion and several others. You never commented. I guess you figured it wasn't worth reading since you didn't write it or do the analysis.

I said we didn't look at what SAI does to the results. I didn't see any analysis by you or anyone else on that factor and how it relates to increased camber gain.

I guess now you can't even admit you were wrong on the tire scrub, even though I showed you how I calculated it. I was using Rocky's setup and you said the C3 camber gain was "similar to" the extended balljoint. So now you just drop the subject instead of commenting on it? I stand by my tire scrub numbers unless you can show where they're wrong...how did you get yours?

I'm done on this thread. If you guys want to discuss suspension geometry with me, post your comments on the suspension analysis thread. There's a lot of bad numbers and off-topic posts in this one, that's why I started the new one. ;)

[Rick_L]

Go back and read the later thread. Your statements are not accurate. I presented an analysis for 55-57 stock, 55-57 2" cut spring, 55-57 dropped spindle, 55-57 extended ball joint, 55-57 C3 spindle, early C4, and late C4. You obviously didn't read any of it.

I still disagree with the scrub analysis. Maybe a definition problem.

But after all you're never wrong, in your usual manner. I'm done with all this until you pull your head out of your ass.