Will 78 Camaro chassis work with 57

[goob8869]

I was looking to upgrade the front suspension on my 57 and a friend of mine has a 78 Camaro front clip with tubular a arms and coil overs. Will this front work with my 57 chassis. I also have someone else with a 57 chassis with a fat man fab front clip installed wanting to trade even on my stock 57 chassis. Which would be the best route to go.

[chevynut]

Welcome to the site, goob!

IMO neither is a very good upgrade. The camaro clip is a lot of work and will improve the handling to 78 standards. It will "work" but you still have to fab the radiator support and bumper mounts and get the correct ride height set. The mounting surface width is 61.5" which is about 2" wider than stock tri5. I've seen it done, and some people say it detracts from the value of the car. The Fatman clip is based on a Mustang 2 suspension, if I recall correctly. I think that stuff should be left to street rods as it's decades outdated. I always thought the typical MII upper a-arm attachment left a lot to be desired.

Some will say that you can upgrade a stock frame with bolt-on parts to perform like a modern car, but it can cost a lot and not give you modern car handling. It can be improved with some limitations. I've known guys to pay $5-6K on bolt-on stuff and still not get what they wanted or expected.

Check out my website link below for what I feel is a better option if you want a more modern performance suspension. :)

[goob8869]

I would love to go that route if I had 6k lying around to use on it.

[Rick_L]

Goob, remember this - there is nothing that the Camaro clip does for you that can't be done using the stock frame, and using the stock frame is a lot more straightforward and cheaper.

[goob8869]

The reason I was considering the camaro frame is because it has tubular control arms, coil over shocks, and rack and pinion already installed

[chevynut]

I would love to go that route if I had 6k lying around to use on it.

Goob, I don't know where you're getting $6K from ;). That's my price for a full C4 conversion frame. If you're just wanting a different front suspension, my basic clip is $2195 and the full clip is $3195. You can buy a complete C4 front suspension for $500-800 that includes all the suspension parts, disc brakes, steering rack, and swaybar if you shop around. Some guys get the suspension for free by buying a donor car and selling off the unwanted parts.

If you can do some of the fab work yourself, the basic clip is a good foundation for a modern performance suspension. It's far better than any Camaro or Mustang II setup, imo. The suspension geometry is better, the steering rack is better, and the brakes are better. The project can be done for around $2700 if you do your own welding and some fab work, which it sounds like you're capable of doing if you're considering the Camaro clip.

Rick is right, the Camaro setup won't get you any better suspension than you can get with bolt-on parts. But the cost of new a-arms, dropped spindle kit, disc brakes, a new steering box or rack, swaybar, and all the other stuff you need really adds up.

[goob8869]

Goob, I don't know where you're getting $6K from ;). That's my price for a full C4 conversion frame. If you're just wanting a different front suspension, my basic clip is $2195 and the full clip is $3195. You can buy a complete C4 front suspension for $500-800 that includes all the suspension parts, disc brakes, steering rack, and swaybar if you shop around. Some guys get the suspension for free by buying a donor car and selling off the unwanted parts.

If you can do some of the fab work yourself, the basic clip is a good foundation for a modern performance suspension. It's far better than any Camaro or Mustang II setup, imo. The suspension geometry is better, the steering rack is better, and the brakes are better. The project can be done for around $2700 if you do your own welding and some fab work, which it sounds like you're capable of doing if you're considering the Camaro clip.

Rick is right, the Camaro setup won't get you any better suspension than you can get with bolt-on parts. But the cost of new a-arms, dropped spindle kit, disc brakes, a new steering box or rack, swaybar, and all the other stuff you need really adds up.

Sorry chevynut was in a hurry when I checked out the site and misread it. I can do the welding and fabricating that needs to be done and I'm interested in your setup. Will I have to run a flat face wheel with this setup or can I have some lip? Thanks for help

[chevynut]

Goob, The early C4 front end is 61" wide at the wheel mounting surfaces so it's 1.5" wider than a stock tri5 front end, but a little narrower than the '78 Camaro front end you mentioned. The late C4 front end is 62" wide.

This Nomad has the late ('88-'96) C4 front end with Coddington wheels with 245-45/17 tires. It also has an early C4 rear with 275-45/17 tires.. You don't have to use Corvette wheels, just a wheel with the right offset. The offset kind of depends on tire size you choose. A smaller tire can have slightly less positive offset.


http://www.wadesgarage.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3499&g2_serialNumber=2

http://www.wadesgarage.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=3494&g2_serialNumber=2

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

You can do a complete bolt on setup which includes upper arms, performance drop springs, new 500 steering box, disc brakes, shocks, & front sway bar for about 2700$ as a comparison. If you need your current steering link etc serviced you will have to add the cost of that on top of what I quoted.

Cnut does you estimate include the cost of front coilovers?

[chevynut]

Rocky, no it doesn't include coilovers because they're not required. The C4 spring works fine and coilovers are optional and probably add around $500. You would have to add shocks.

Personally I'd go with dropped spindles instead of dropped springs. Dropped springs reduce the suspension travel and the most I'd go on them is 1" lower. Our conversions drop the front suspension 3" from stock with an option for 2" drop. Dropped spindles add about $350 to that price. And the bolt-ons won't match the C4 performance at about the same cost. Plus the C4 suspension is around 75-100 pounds or so lighter.

There are other small costs as there are with any modification. With either one you need a new column and steering linkage. The C4 suspension may or may not require some refurbishing, depending on condition.

[LEE T]

How much drop on that blue nomad, front and rear?

[chevynut]

Lee, the blue Nomad is dropped 3" in front and 2" in the rear. That's our standard configuration. That's only the suspension drop, and tires can drop it even further if they're smaller than the 28.3" stockers. With a 26" tire the frame is about 4" off the ground at the front of the door where it kicks up which is about as low as I recommend going. Here's pics of it finished:


http://www.trifivechevys.com/attachment.php?attachmentid=5394&stc=1

http://www.trifivechevys.com/attachment.php?attachmentid=5395&stc=1

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

Are stockers really 28.3? I thought more like 27?

[chevynut]

Stock tires on 55-56 were 670-15. The LOADED rolling radius was specified at 13.4" (per GM specs) which makes them 26.8" loaded. I think the unloaded radius is at least 1/2" larger. Somewhere I found the 28.3" dimension at one time.

[markm]

Upgrade cost to stock depends a lot on who you are, I spent about half the 2700 quoted above on Steering and brake upgrades. Yes I have a 500 PS box, ft. disk, Ft. & Rr. sway bars.

[chevynut]

I spent about half the 2700 quoted above on Steering and brake upgrades. Yes I have a 500 PS box, ft. disk, Ft. & Rr. sway bars.


When, in 1970? ;)

Based on Summit Racing's prices the CPP 5000 power steering box is $420 alone. Upper a-arms are $360 from CPP and lowers are $780 from Heidt's. A CPP dropped spindle kit with disc brakes is $700. Hotchkiss swaybar kits are $300 each. That's $2860 plus shipping.

Sure you can buy inferior parts for less, if that's what you want. And you might argue that you don't need the lower a-arms.

Now add the longer upper balljoints that Rocky recommends to correct the suspension problems for $160 a pair and you're over $3000. And you still end up with a suspension that's inferior to a C4 setup. ;)

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

Drop spindles are junk I don't really understand your or anyone else's reason to keep using them. The result you get is this.

" I've known guys to pay $5-6K on bolt-on stuff and still not get what they wanted or expected. " as you stated above.

[markm]

I do not run dropped spindles. Nor did I buy bunch of cheap parts, my rotors are low mileage 72 Monte Carlo.

[chevynut]

Drop spindles are junk I don't really understand your or anyone else's reason to keep using them.

Because they're the best way to drop a car 2". Dropped springs reduce suspension travel and screw up the suspension geometry. The lower a-arms and steering rod ends on a tri5 or just about any car are DESIGNED to be level at ride height. Dropped spindles maintain that geometry. If the a-arms are angled so the lower balljoint is 2" higher at ride height any compression or extension of the suspension causes the lower balljoint to move in and out, scrubbing the tire. To me that's screwed up. Dropped spindles maintain the designed geometry. A taller spindle would be better and I wonder why nobody offers one.

The other thing that happens is the roll center drops with the balljoint above the a-arm pivot, causing the car to want to roll more.

[chevynut]

Rocky, I have never disputed your claim that a taller balljoint in the upper a-arm will make the stock suspension work better. If you raise the balljoint enough it moves the instant center from the outside of the vehicle to the opposite side. Anytime you have an instant center outside the vehicle (on the same side) the roll center will be below ground, which is bad as it will cause the car to roll more.

What I have a dispute with you about is the effects of dropped springs versus dropped spindles.

The stock suspension is designed to put the lower a-arm level on most cars. This is to minimize the side to side movement of the lower balljoint. When you add the taller balljoints, the instant center will be NO LOWER than the lower balljoint centerline, inboard of the a-arms or on the opposite side of the car. When a line is drawn to the tire contact patch, it will ALWAYS result in a roll center that is above ground. The taller the spindle, the more camber gain because the upper a-arm angle is increased. It also raises the roll center.

Now let's look at the situation with 2"dropped spindles. The lower balljoints are 2" lower to the ground, but so is the CG of the car so the distance from the CG to the roll center doesn't change. The contact patch doesn't move.

When you add 2"dropped springs, you've raised the lower balljoints 2" ABOVE the inner pivot. Now the lines drawn through the lower balljoints and the pivots hit the ground at some point on the opposite side of the car. When you draw a line through the UPPER balljoint and pivot, it intersects the lower line at a lower point than if the lower a-arm was level. So you have lowered the roll center relative to the CG, even though the CG also moved downward.

With an increase in distance between the roll center and the CG the car wants to roll a lot and will need stiff springs to control it. With a smaller distance between the roll center CG the car doesn't want to roll as much and can use softer springs. For a nice ride, I prefer softer springs. So not only will the car ride better and smoother, it will handle better with dropped spindles instead of cut springs. And you have the option to increase the spring rate a little if you want to plant the tires better, but you don't need as high or a rate to control body roll.

[chevynut]

Drop spindles are junk I don't really understand your or anyone else's reason to keep using them.


Rocky, now that I've AGAIN taken the time to explain why dropped spindles are better than dropped springs, why don't you explain to me why you think dropped springs are better? I forgot to mention the bump steer issues with the dropped springs.

All you do is call them "junk" but I don't recall you ever giving a good technical explanation why you think the dropped springs are better. And please don't whine about me "bullying" you. :)

I think too many guys are using 2" dropped springs based on bad information and don't know the detrimental effects on their suspension geometry. By the way, I've never used dropped spindles on any car myself. ;)

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

Cnut I already showed you on paper why in the case of a trifive chevy drop spindles are not a wise chose if your goals are to improve the handling of the car. Using drop spindles leaves the roll center in left field and does not correct the suspension issues. Not here to argue in a perfect world perhaps the lower arms should he horz but installing a drop spring in a trifive does not make the arm go up hill enough to effect the roll all that much. The car also needs stiffer springs as do all performnce cars including your c4 setup than what a stock trifive spring has. If your goal is to slam your trifive in the weeds and look cool then drop spindles are the ticket. I believe there are a few companys that build performance drop spindles with there arms. Chassis works I belive but the price point is so high not in the price point of this conversation. Cost as much as your complete chassis lol.

Do you know what spring rates the stock C4 cars had? I read pretty intersesting story about that topic yesterday. Seems like customer feed back after the 84 year made GM soften the ride abit.

depending on your customers year selection might be quit different from anothers using stock equipment lol. Big changes in spring rates.

http://www.corvetteforum.com/forums/c4-tech-performance/3612068-comparing-spring-rates-84-96-z51.html

[markm]

Let me get this right you guys like the stance of that blue Nomad, it reminds me of a buddies unrestored 210 wagon with wore out springs.

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

Let me get this right you guys like the stance of that blue Nomad, it reminds me of a buddies unrestored 210 wagon with wore out springs.

LOL!!! Can you believe a person would take a beauty like this
http://i282.photobucket.com/albums/kk243/rockytoppers1/IMG_9114.jpg

and do this to it lol.

http://i282.photobucket.com/albums/kk243/rockytoppers1/rtmad2.jpg (http://s282.photobucket.com/user/rockytoppers1/media/rtmad2.jpg.html)

[Rick_L]

mark, do you use snow tires on your cars?

[markm]

No need I have two 4x4 GMC trucks and a 72 K/5 Blazer. I still have a pair of stock 56 wheels I bought in the early 70s for my 56 for that purpose. I would have to pull the axles and turn the register down for them to fit now.

[chevynut]

Cnut I already showed you on paper why in the case of a trifive chevy drop spindles are not a wise chose if your goals are to improve the handling of the car. Using drop spindles leaves the roll center in left field and does not correct the suspension issues.

Rocky, the dropped spindles aren't what puts the instant centers in "left field" it's the angle of the upper a-arms. I think you're not understanding what you're doing to your front suspension. Raising the upper a-arms with lengthened upper balljoints moves the instant center of the front suspension from WAY outside the car on the same side as the a-arms to a point on the opposite side of the car. Simply adding dropped springs does not fix that problem, because the spindle stays the same length and the relationship between the upper and lower a-arms doesn't change. I'm betting the instant center with 2" dropped springs is still out in "left field".

With the lower a-arm level, the instant center is at the same level as the lower a-arm pivots and the distance away is controlled by the upper a-arm angle. With the instant center at that level, the roll center will ALWAYS be above ground. By raising the spindle on the knuckle you get lowering of the car WITHOUT adversely affecting that geometry.

What you've done with dropped springs is caused the lower a-arm to angle down like the upper a-arm. That will put the instant center LOWER than it will be with a level lower a-arm. I haven't laid it out to be sure, but the instant center could very well be below ground, which will put the roll center below ground.

The net result is that you save a few bucks on the dropped spindles, but you've screwed up your suspension geometry and moved the roll center away from the CG. You keep saying your suspension will be "close" to a C4 but it's nowhere close to being comparable if you do that.


Not here to argue in a perfect world perhaps the lower arms should he horz but installing a drop spring in a trifive does not make the arm go up hill enough to effect the roll all that much.

Yes it does. Lay it out. How much do you think is detrimental? I've searched the net about this and there's a lot of info on not having the lower a-arm level, and the negative effects of that. To me, dropped spindles make a lot more sense.


The car also needs stiffer springs as do all performnce cars including your c4 setup than what a stock trifive spring has.

Of course. The tri5 springs are really soft. With the lower a-arm dropped like you're doing, you need to use a stiffer spring than you would otherwise need. If you don't mind the harsh ride, maybe that's ok. But it doesn't address the tire scrub and the bump steer issues it creates. And you lose some camber gain as well, his already weak even with the slightly taller balljoint.


If your goal is to slam your trifive in the weeds and look cool then drop spindles are the ticket.

Drop spindles drop the car 2" which is the same as you say you're doing with 2" drop springs. The dropped spindles just don't screw up the geometry.


I read pretty intersesting story about that topic yesterday. Seems like customer feed back after the 84 year made GM soften the ride abit.

That doesn't surprise me as some of the early cars had very high spring rates, a lot higher than necessary.

Bottom line is that your claim that dropped spindles are "junk" is unsubstantiated, but cutting springs such that the lower a-arm is 2" higher at the balljoint than the pivot causes a lot of detrimental effects. ;)

[chevynut]

Let me get this right you guys like the stance of that blue Nomad, it reminds me of a buddies unrestored 210 wagon with wore out springs.

We can't help it that you're stuck in the 60's. Have you even driven a car newer than 1980? Maybe you don't even know what a modern car's supposed to handle like. :)

[chevynut]

Rocky, how much have you actually dropped your car? It doesn't look that low to me. I mean by measurements, not what you did to it.

The stock distance between the rear axle and the bottom of the frame is 5.725". I don't remember how to measure the front but there is some measurement between the lower a-arm pivot and the bottom of the spindle, or something like that. How much higher is the lower balljoint center than the a-arm pivot?

I went and looked back at your diagram and your lower balljoint is only .82" above the pivot in that drawing. I thought you said you lowered it 2" with dropped springs.

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

Cnut thats were your wrong or misstated above. The drop spring raise the lower arm it points up slightly. With the addition of the taller ball joint and ajustable arm the upper arm is also moved up more because you made the bottom swing upward. Your suspension now has the roll center in the center not in left field anymore and your suspension operates in negative camber from the start of the turn as it suppose to. Using drop spindles drops the car but does not correct the camber and the results are less than desirable. The upper arm does not move upward enough.

My car is right at 2 inches lower than stock based on the factory manual and distance from the lower arm pivot to ground measurement. Remember rule of thumb 1 coil = 2inches drop in height. One coil cut is less than 2 inches at spindle because of the radius so arm does not swing up as much.

[markm]

We can't help it that you're stuck in the 60's. Have you even driven a car newer than 1980? Maybe you don't even know what a modern car's supposed to handle like. :)

My 67 SS 350 drove like crap when I got it, it has received numerous comments about how well it drives now. Secret, I replaced the slow pre-variable ratio PS box with one from a 77 Z28. Since it has retired from bracket racing getting rid of the 90/10 shocks for gas also helped. This car has factory disk converted to D52 calipers.

I really like my late model Impala I have upgraded the tires to Goodyear RSA with a high speed rating. I have driven a new Caddy quite a bit and you are correct, I really don't care for it or its rubber band tires.

[chevynut]

The drop spring raise the lower arm it points up slightly. With the addition of the taller ball joint and ajustable arm the upper arm is also moved up more because you made the bottom swing upward. Your suspension now has the roll center in the center not in left field anymore and your suspension operates in negative camber from the start of the turn as it suppose to. Using drop spindles drops the car but does not correct the camber and the results are less than desirable. The upper arm does not move upward enough.

Not sure how I missed this reply ;), but angling the lower a-arm UP on the outboard end causes the roll center to DROP as I've pointed out several times. You shift the instant center to the opposite side of the car with the taller spindle or taller upper balljoint, not by tilting the lower a-arm. When you tilt the lower a-arm you put it into a situation where it's getting shorter as the suspension is compressed, and that not only scrubs the tire more but it also negates some of the negative camber gain. Search the internet and you'll find lots of comments about how a lower a-arm angled up at the outboard end is bad. I dunno, maybe you're more concerned about camber gain than you are dropping the roll center or scrubbing tires? :confused:

Also, I don't see where an adjustable upper a-arm really does anything to improve the suspension geometry if you're using a stock lower a-arm. You can accomplish the same thing with shims and a stock upper a-arm and offset shafts, if needed. I find it hard to believe that a 1/2" taller balljoint would require a different upper a-arm length. The caster is a different issue, but it can be fixed with non-adjustable a-arms too, or offset shafts.


My car is right at 2 inches lower than stock based on the factory manual and distance from the lower arm pivot to ground measurement. Remember rule of thumb 1 coil = 2inches drop in height. One coil cut is less than 2 inches at spindle because of the radius so arm does not swing up as much.

That's interesting. I don't remember how the shop manual says to measure the ride height but according to your measurements your lower balljoint is less than 1" above the a-arm pivot. I know on some say the center of the balljoint should be slightly below the lower a-arm pivot so the suspension works on both sides of a level lower a-arm. I don't know about those "rules of thumb" on cut springs because it's dependent on the weight of the engine too.

The pitch of the first coil on a stock spring is 1", the rest are 1 3/4" (I measured them ;)). The balljoint is 14.5" from the pivot and the center of the spring is at 9.5" from the pivot so the motion ratio of the lower a-arm is 14.5/9.5 or 1.53. So if you cut one coil off the spring you've shortened it by 1" and the spindle should theoretically move up 1.53". However, you also slightly increased the spring rate by removing a coil so the drop will be slightly less than that. Cutting 2 coils gives you a huge drop.

It would be interesting to see the actual suspension geometries comparing a taller balljoint and dropped spindles and a taller balljoint and dropped springs. I'm certain that the dropped spindle will give you a higher roll center, but not sure about the camber gain difference. With the lower a-arm level or slightly low at the outboard end, the instant center (static) will always be above ground and as a result the roll center will always be above ground ....in your case with the tilted lower a-arm the instant center AND roll center can actually be below ground. That's not a good situation for handling.

However, I think I'm understanding where you're coming from on the camber gain. You are "artificially" adding more upward tilt into the upper a-arm with the dropped springs, so you believe that will increase camber gain. I'm not sure of that since you also raised the lower a-arm balljoint above the pivot, which will tend to decrease negative camber gain as it moves up (and scrub the tires).:p

I have to ask....why don't you go with a 3/4" or even 1" taller balljoint instead of just 1/2" taller? You only increased the spindle height to be barely longer than the distance between the a-arm pivots. I still don't understand why nobody makes a taller spindle for these cars when there are all sorts of spindles out there.

[Rick_L]

Changing the ride height with springs isn't going to change camber gain.

What it will do is lower the cg of the car which is good.

I have kept out of this discussion because I haven't recently had access to CAD layout tools. I now have that again so I may investigate more and make comments.

One thing I'm wondering here is whether you've considered what's happening with the wheel that's in extension when cornering.

[chevynut]

Changing the ride height with springs isn't going to change camber gain.

I think maybe you're missing the point ;). There are two scenarios we're discussing.

1. Extended length (1/2") upper balljoint with 2" dropped spindles. Lower a-arm is level at ride height. Car is aligned to proper camber specs. Instant centers are on the opposite side of car level with the lower a-arms, and therefore roll center is above ground level. Negative camber gain occurs as soon as suspension is compressed and increases the more it's compressed.

2. Extended length (1/2") upper balljoint with 2" dropped springs. Lower a-arm is pointing up and out, 2" higher at balljoint than at pivot. Car is aligned to proper camber specs. Instant centers are on the opposite side of car and will be LOWER than if the lower a-arms were level, possible below ground level. The roll center is LOWER than in scenario 1, and is possibly below ground. Body roll is increased over scenario 1. Since the lower balljoint is moving toward the center of the car on compression and away from the center of the car on extension, some tire scrub will occur.

Both scenarios lower the CG the same amount. I don't know what happens to overall camber gain in scenario 2, but the lower balljoint is moving inboard as is the upper one. So it seems like the camber gain would be decreased...maybe not. Scenario 2 is NOT the same as scenario 1 with the suspension compressed an additional 2".

In reality the increased height of 1/2" at the upper balljoint isn't very dramatic imo. It moves the upper balljoint from 1/4" below the pivot to 1/4" above the pivot. It's likely that a slight compression of the suspension would result in close to the same thing. In other words, if the springs were sagging a bit (1/2"), you could have the same upper a-arm position as you have with the longer balljoint. The lower a-arm would be slightly angled as well, but it seems to me that you might have moved the instant center to the opposite side of the car by just dropping the stock suspension a little since the angle of the upper a-arm changes faster than the angle of the lower a-arm. I would need to see that in CAD or some suspension design software to be sure.

To me the bottom line is that I think the effects of these longer balljoints are over-stated and don't make that much difference in handling by themselves with everything else kept constant. The stuff I read about making the steering "more responsive" and other "amazing" comments just seems a little outrageous to me. It's a move in the right direction, but it doesn't seem very significant. I'd like to drive a car before and after this change, and ONLY this change (plus correct alignment).

Oh, and one more thing....increased caster will increase the camber in a turn. It seems like SAI will have an effect on camber in a turn too. So these things all work together to try to keep the contact patch flat on the road when the body wants to roll. When the body rolls, camber is decreased.

I wish we had some software that could analyze these things throughout the range of motion, to see what the roll center does dynamically.


One thing I'm wondering here is whether you've considered what's happening with the wheel that's in extension when cornering.

It seems like you would want it to go to positive camber:confused:. Good question and interesting topic.

[chevynut]

Here's some very interesting info on the effects of caster and SAI on camber as a car is steered.

http://ismasupers.com/downloads/tech-talk/Tech-02%20Suspension%20Geometry%20relations%204.pdf

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

Here is a trifive stock specs see link. This is how I determined I'm approximately 2 inches lower than stock. You will note that the upper arm is dramatically pointing down. The stock aligment specs are not good compared to a modern car with modern alignment specs. My lower arm is only about 1/2 in up hill from so called perfect horz. Putting drop spindles in will have no effect on changing the relation between the upper and lower arm so you have done nothing to improve the suspensions bad geometery. The arms instance center is on the wrong side of the car in stock form so not sure were the roll center is. In the case I'm presenting using drop springs in cunjunction with the taller ball joints the instance center gets moved to the correct side of the car and puts the roll center in the center just above the ground. The upper arm gets moved up above the horz and generates negative camber as it is suppose to. Approximately 1 deg with 2 inches of suspension travel the scrub appears to be about .13 inboard. Not sure I can explain it in any better way. You would have to install a very tall upper ball joint which would most likely overstress the stock spindle and I'm not sure it would even fit if your are running a stock track width or close to it like me, see picture below. It would have to be a very tall drop spindle. None exist to my knowledge. I really dont know what effect moving the wheel axle in relation to the arm pivots is good or bad so I cannot speak to that.
Rocky

http://www.trifive.com/garage/57%20Chevy%20Assembly%20Manual/3-3.gif



http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_155.jpg

[Rick_L]

Cnut, interesting article. I can't comment yet, as I speed read it, need to think about what's said and draw some diagrams.

One needs to think about what happens with just a few degrees of steering angle - anything more is parking not driving.

Also, on the lower arm angle - keep in mind the ball joint is lower than the arm itself, and the line between the inner pivot shaft and the ball joint centerline is what counts. So you have an appearance of the arm going uphill more than it really is.

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

Pictures worth a thousand words as they say. Note how far down the lower arms point on a stock 55. The second is a cad model showing the relation of a stock trifive suspension or drop spindle suspension compared to drop springs and taller upper ball joint. The latter is clearly better and closer to what Cnut states is idea suspension geometery. The dark blue lines represent the stock or drop spindle arm angles in static. The red lines represent the drop spring arms with taller ball joints in static. Light blue lines represent the dynamic movement of the drop spring taller ball joint configuration with 2 inches of suspension travel. It is a very dramatic change for the better. This is why I call drop spindles junk.
http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_157.jpg


http://i282.photobucket.com/albums/kk243/rockytoppers1/Mobile%20Uploads/image_156.jpg

[Rick_L]

Ok, I'm tooled up to diagram this stuff. I dug up a diagram that I did in 2009, but I think it's incomplete in some ways. Either that or I haven't figured out all the things I diagrammed.

For anyone that's interested, I downloaded "Drafsight" from Dassault Systems. Essentially it's AutoCAD Light, it's free, and has some support. So far it acts just like AutoCAD for the simple stuff I've tried. And that's all I expect from it. It probably (actually certainly) doesn't have all the bells and whistles of acad, but that's actually good.

For comparison sake, what are the significant dimensions you guys are using? I think I saw them listed in someone's post, but couldn't find it just now. I don't want think small differences in the starting point pollute the results much, but I don't want that to be a discussion item.

Cnut, why does the location of the instant center being on one side or the other bother you? Seems to me that the location of the roll center is the important thing.

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

Rick you are correct. I put my arms horz and the the delta in roll center is less than .56 pretty much mute point. My model does not have good stock suspension data points they are based off my cars modified suspension and only assumed based on the cars 2 inch height delta.

[chevynut]

Here is a trifive stock specs see link. This is how I determined I'm approximately 2 inches lower than stock.

Well, that "A" dimension you mention is irrelevant unless your tires are the same height as stock. If your tire radius is less than the stock tire dimension, you need to subtract that from the "A" dimension. Note in the drawing they show the inner pivot at the same height as the balljoint at ride height. IMO your car isn't dropped 2" based on the GM diagram.

http://www.trifive.com/garage/57%20Chevy%20Assembly%20Manual/3-3.gif



You will note that the upper arm is dramatically pointing down.

I've never disputed that and I agree it's a bad design. Note, however, that the lower a-arm is level and the a-arm pivot is the same height as the center of the balljoint in the diagram....you seem to want to ignore that.


The stock aligment specs are not good compared to a modern car with modern alignment specs.

Who's talking about alignment? You again seem to be confusing alignment with geometry. Alignment is static caster, camber, and toe. The geometry is mostly non-adjustable and is determined by pivot points, arm lengths, spindle height, and upper a-arm angles.


My lower arm is only about 1/2 in up hill from so called perfect horz.

Then I say your car IS NOT dropped 2" from stock. Based on the diagram, your "A" dimension should be 10.49" with the stock size tire, or 10.49" minus the difference in your loaded tire radius from a loaded stock tire. Radials seem to flatten more with load than the original bias ply tires. The original tires were 670-15.


Putting drop spindles in will have no effect on changing the relation between the upper and lower arm so you have done nothing to improve the suspensions bad geometery.

Dropped spindles lower the CG which is a good thing. Nobody said it affects the suspension geometry. In fact, it PRESERVES the correct lower a-arm angle.


The arms instance center is on the wrong side of the car in stock form so not sure were the roll center is.

It is below the ground in the center of the car.


In the case I'm presenting using drop springs in cunjunction with the taller ball joints the instance center gets moved to the correct side of the car and puts the roll center in the center just above the ground.

It is an improvement from stock, which I have not disputed. But the roll center using your drop springs is LOWER than where it would be with dropped spindles and the same taller balljoint. I've always agreed that the taller balljoint is a good thing...in fact I'd go longer than 1/2" for further improvement. The dropped springs make the lower a-arm angle up which moves the roll center away from the CG, increasing the length of the roll moment, which causes the body to roll more. Simple fact.


The upper arm gets moved up above the horz and generates negative camber as it is suppose to. Approximately 1 deg with 2 inches of suspension travel the scrub appears to be about .13 inboard.

That seems like a lot of scrub, and very little camber gain. Keep in mind that as the car rolls, the camber is reduced. So because you moved the roll center down it's going to roll more. Dynamically, I'm betting that 1 degree of camber is negated by body roll. All it takes is 1 degree of body roll at 2" os suspension compression and your 1 degree of camber is gone. That's why I'd keep the lower a-arm level or pointing slightly DOWN at ride height and using an even taller balljoint for more camber gain.


You would have to install a very tall upper ball joint which would most likely overstress the stock spindle and I'm not sure it would even fit if your are running a stock track width or close to it like me,

I wouldn't worry about stressing the spindle, as there's not much stress on the upper a-arm or balljoint except in the case of braking. Even in hard cornering the upper balljoint merely resists the spindle rotation around the lower balljoint, which takes most of the load. I can see that there's a point where a small wheel might interfere with the balljoint. I doubt a 3/4" or 1" taller balljoint would make that much difference, but there are larger wheels available too.


It would have to be a very tall drop spindle. None exist to my knowledge.

I thought the "taller spindle" was the whole point of your tall balljoint. So why not use one taller than 1/2" over stock and make the efffective spindle height even taller?

[chevynut]

Pictures worth a thousand words as they say. Note how far down the lower arms point on a stock 55.

If that's truly a "stock" 55 then the suspension height doesn't match the GM drawings, which shows the lower a-arm level. I'm skeptical whether that's really the stock height without verifying the dimensions. Where did that pic come from? If it's a restored car, it's hard telling where it's really sitting. If it's a picture from the 50's of an actual production car, then their drawing doesn't match.


The latter is clearly better and closer to what Cnut states is idea suspension geometery.

IMO the lower a-arm should be level to slightly low on the outboard end and that's what suspension designers say as well. That's ideal, not high on the outboard end. Actually having the lower a-arm angled down to the outboard end increases camber gain for the first few inches of travel. You get the CG drop with dropped spindles while maintaining ideal lower a-arm position.


Light blue lines represent the dynamic movement of the drop spring taller ball joint configuration with 2 inches of suspension travel. It is a very dramatic change for the better. This is why I call drop spindles junk.

Yet you didn't show the stock suspension in compression for comparison. And what is the angle of your dark blue line, and where did you get it?

[chevynut]

Cnut, why does the location of the instant center being on one side or the other bother you? Seems to me that the location of the roll center is the important thing.

Rick, with the stock upper a-arm pointing down the instant center is outboard of the car on the same side as the suspension in question. When you draw a line from the instant centers through the tire contact patches to get the roll center, it will be below ground and far away from the CG.

With a level lower a-arm the instant center will always be at the height of the lower balljoint. With the lower a-arm angled down to the outside, and with the stock spindle height, the instant center will drop, and the roll center will rise.

Now, with a taller balljoint and a level lower a-arm, the upper a-arm is pointing up and outboard. The instant center has now flipped to the opposite side of the car, at the height of the lower balljoint. A line drawn from the instant center to the contact patch of the tire on the SAME SIDE as the suspension will be ABOVE ground. This moves the roll center closer to the CG.

With the taller balljoint and the lower a-arm pointing up at the ouboard end, the instant center moves down on the opposite side of the car. That moves the roll center down, away from the CG. The more you raise the end of the lower a-arm, the more the roll center drops.

With the dropped spindles, longer balljoint, and level a-arm, you get the CG drop, the benefit of moving the instant center to the opposite side of the car, and the corresponding increase in camber gain, as well as a higher roll center which helps reduce body roll.

Clearly that makes the dropped spindle solution superior to the cut springs, if the cut springs result in a lower a-arm pointing up and outboard.

[chevynut]

FWIW the GM specs say that a 6.70-15 tire turns 755 revolutions per mile. That gives a loaded rolling radius of 13.36". A BFG 255-45/17 tire is 798 revolutions per mile for a 12.63" loaded radius. That's a difference of .73".

So to get stock suspension stance your "A" measurement should theoretically be 9.76" assuming those tire specs are correct. With a 2" drop it should be 7.76".

Apparently there's some discrepancy in the GM drawing and the actual suspension component positions. But the conclusions above are still the same.

[chevynut]

Rick, here's the thread with the dimensions:

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

[chevynut]

Rick you are correct. I put my arms horz and the the delta in roll center is less than .56 pretty much mute point.

Then you're calculating the roll center incorrectly. ;)

With the a-arms level your instant center will be 7.31" above ground regardless of the upper a-arm angle, since that's where you say your inner pivot is. The instant center will be fairly far out on the opposite side of the car with the slightly longer upper balljoint, but the roll center WILL be above ground. I laid it out in CAD using your dimensions from the other thread and the roll center is 1.187" above ground because the instant center is so far from the center of the car. It's about 286" away from the tire centerline.

With both a-arms pointing downward toward the center of the car, the instant center is closer to the center of the car at about 170" away from the tire centerline. Using your geometry, the roll center is .36" below ground. And it's 1.55" below where it is with the lower a-arm level.

The more you lower the car with dropped springs, the more you drop the instant center and the more you drop the roll center. Based on the GM drawings, it looked to me like your lower a-arm would be at a lot more angle...like 2" higher at the outboard end than at the pivot with 2"drop springs.

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

Again there was no need for another thread and another wasted effort on you guys part. You or Rick in no way Can Accurately analysis my setup better than I already have. My analysis presented here is very accurate based off real measurements on a real car with the correct hardware aligned to 5 degree caster -1 degree camber. If your doing anything else it is totally garbage. My upper arm has a fixed pivot no shims. The arm length is adjustable in length the pivot don't change. Its 4 inches outboard of the lower arm measured from the floor with a framing square. It is no were the new claimed 5 inch delta.

My car is lowered approximately 2 inches from stock based on the curb weight dimension A of 10.49 inches. My tire is a 205/75/15 27.1 dia. My dimension is 7.7 inches. Again the arms on a stock trifive point down way down from horz. The picture in dispute came from here. http://www.motortrend.com/news/c12_0612_1957_chevrolet_bel_air/ there aint anything fake about it. My analysis also backs this up. You simple move the lower arm down 2 inches from my real measurment. This is about as close as you are going to get to determine the official angle of the lower arm without measuring a real stock car with stock tires. You can also play with the lower arm 1/2 inch up or down and the results want change much.

We should also note that Cnuts contradicts his on definition of how to establish roll center. You cannot get a roll center defined in the stock setup. The arms never interesect to etablish one using the criteria shown. Again roll center on a stock trifive is in left or right field not on the centerline. So any thing said about roll center height is miss information if you are trying to compare the 2 you can't.

I'll rest my case my work is shown nothing hidden.

[Rick_L]

Rocky you are confusing the instant center of motion of the suspension with the roll center.

The instant center is the location where lines through the control arms' centers intersect. This will be on one side of the car or the other. If the control arms are parallel, then the instant center is at infinity.

The roll center is the vertical location of a line drawn from the instant center (above) through the center of the tire contact patch to the car centerline. If the instant center is at infinity, then the line through the contact patch is parallel to the lines from the upper and lower control arms. Note that this line doesn't have to be parallel to the ground, it's parallel to the control arm planes. It is parallel to the ground when the control arms are too.

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

Rick the instant center per the diagram is the intersection point were the upper and lower arm lines cross. The roll center is the intersection of a line drawn thru the instant center and tire contact point. Am I'm wrong? Assuming I'm not both arms on a stock setup point down and out board and the intersecting point of the arms are on the wrong side of the car way below ground. How does one then derive the roll center of the stock setup?

[Rick_L]

You're right on the roll center construction - in your latest post, not in the previous one, at least as I read it.

Roll center is still the same way. A line from the instant center through the center of the tire patch is drawn, and the roll center height is where that line crosses the center of the car.

The difference is this -
When the i.c. is outboard, you extend the line to the center of the car to get the roll center. If the i.c. is low, the roll center will be higher than the ground.
When the i.c. is inboard, the center of the car is along the line. If the i.c. is low, the roll center will be low but below the ground.

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

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

[Rick_L]

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.

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

Rick I respect your reply I'm not one with knowledge to dispute or try to be negative about your comments but why does the link I posted about how to make car handle above abort discussion about ic on wrong side? Another words it don't back up your statements or better said never goes there?

[Rick_L]

All I can say is that they said F1, the best handling fastest cars on the planet, has the I.C. on the wrong side and they do what they do. So it must not be a fatal flaw.

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

Rick I can not dispute that lol. But personally being a big part of the design and developement of the lasted gen fighters over the past 30 years plus I can assure you the F-16 that is the first fly by wire and was designed when this young pup was a school boy before joining the design team couldn't fly without the computer control to constaintly adjust in real time. The new ones are no different. I suspect the F1 is pretty close to same. Reason it was not included in disussion. But honestly I have nothing to back up that statement other than a guess based on what Ive read about how complex ans adjustable they are real time during a race.