1970 Camaro Tri-4 bar issue

[TBART70]

http://www.artmorrison.com/instructions/tri4-bar1-Model.pdf








I need some help. I have this in my car, it drives well, except for the massive wheel hop. According to the last page of the link, the bars need to be in a certain plane, mine are not like that because of ride height. I can't go low enough to put the bars in the right places. My question is how would you move the bars, lower the front of the bars or raise the rear of them or both? I know I have to do it equal amounts to keep the geometry the same or close to the original design. Or am I missing something else causing the wheel hop, pinion angle, tires too hard, coil-over setting? any suggestions would be welcome. Can you see an easy way to modify the brackets without cutting it all apart? I would also like to put johnny joints in, Art Morrison makes the frames with them now.
Thanks.

-Tom

[dhutton]

I recommend you ask Matt Jones at Art Morrison. He is their design engineer and very helpful in my experience. You could also send a PM to David Pozzi.

Don

[David Pozzi]

First thing I'd check is for play in any of the joints. After that, you are probably right if it's higher than designed height, then it will want to wheel hop. If there's any adjustment on the shocks, try stiffer settings.
As far as modifying, I’d work on the frame mounts.
I'd ask Matt at Art Morrison for advice. He's their engineer and very sharp.

[Marcus SC&C]

That format of suspension is only intended to be run at a single ride height. The height isn`t adjustable so you can put it where you want it, it`s adjustable so that cars of different weights can be adjusted to the one height that works properly. The lack of optional mounting holes for the links is a dead give away (just a heads up for those considering similar systems).
To regain the original geometry (basically a street rod type parallel 4 bar with converging upper links) you`ll have to drop the front of the lower links to make them parallel with the ground (level) at your desired ride height and raise the rear of the upper links to make them level as well. That should eliminate the wheel hop. The suspension will still have less anti squat than the original leaf spring suspension but at least it won`t shake the car apart. If you`d like more traction (who wouldn`t?) add a couple additional holes to allow you to raise the rear of the upper links a little more for more bite. Roll steer will suffer a little bit but there`s quite a bit of happy medium area to play with.

[TBART70]

I'd ask Matt at Art Morrison for advice. He's their engineer and very sharp.

Contacted Art Morrison, I will send them all the info and pics, and see if they can come up with a solution.

Thanks

[TBART70]

From AM

Tom,

I hope all is going well this morning? I just spoke with me lead engineer about your wheel hop, He suggested checking all the pivot points

Too see how loose they might be and your coilover shock setting can or will cause grief. Along with ride height, but in your case the stance and

lower bar angle looks okay.



Hope this helps,

[TBART70]

Nothing is loose, shocks are set to stiffest setting. Should I go softer? Different spring rate? I still think the bars need to be moved.

[dhutton]

Why not try a softer shock setting? What spring rate do you have? Are you running a lot of preload on the spring?

Don

[TBART70]

Why not try a softer shock setting? What spring rate do you have? Are you running a lot of preload on the spring?

Don

I used the coilspring adjuster to raise the ride height(preload). Should I get taller springs to raise the ride height, with a different rate? I have to look and see what the rate is now. ridetech's.

[dhutton]

I would just experiment with shock damping first. I don’t like a lot of preload but have no idea if it would cause wheel hop. I have an assortment of springs here if you want to try a different rate.

Don

[TBART70]

Thanks for the suggestions. I have the intake off right now. Hope to be running again Saturday. Weather is getting colder here and as soon as it snows no more driving. Hopefully I can get it out one More Time.

[TBART70]

12" spring, 2.5 ID, 225 lbs/in
Not sure what direction to go.

[dhutton]

If you are running a lot of preload I would try a 250 lb spring. But only after experimenting with shock damping.

Don

[andrewb70]

I would use whatever spring rate puts the shock in the middle of its travel range. If the spring is too heavy, you may run out of rebound travel on the shock and that will unload the tires.

Andrew

[TBART70]

Think I will call ridetech and get some info, thanks for the help. Any other suggestions are appreciated. Can't drive it now , damn snow!

[marolf101x]

12" 225# springs on the rear of a triangulated 4 link in a second gen camaro sounds about right. For reference our bolt-in 4-link kit uses a 12" 200# spring.

What shocks do you have? Pictures would be great!
Do they have remote reservoirs?

Once I know what shocks you have we'll go from there.

Basic rule of thumb on 4-link rear suspensions. . .the lower bar should be roughly parallel with the ground, the upper bar should be higher at the rear end than it is at the frame.
There's a ton more, but the lower bar is typically the quickest "check" to see where you are.

[dhutton]

I would use whatever spring rate puts the shock in the middle of its travel range. If the spring is too heavy, you may run out of rebound travel on the shock and that will unload the tires.

Andrew

Pretty sure multiple spring rates will get you to ride height depending on how much preload you put on the spring. In my experience with a couple of ridetech setups I found that for street use I prefer as little preload in the spring as I can get away with. The stored energy in a preloaded spring can result in a lousy ride imho. But this is just based on my personal experience and a collection of coilover springs.

Drive a car with a heavily preloaded spring over a pothole and you will quickly get an idea of what I am talking about. Then take that same car with a heavier spring and little to no preload over that same pothole. Day and night in my experience and experimentation. In theory you should be able to address it with shock damping but I was never able to achieve it with single adjustable shocks.

OP says he is running a high ride height and a preloaded spring. This likely means he has less than optimum shock extension travel left. Although I can’t say if this is the cause of his wheel hop I thought it would be worthwhile to experiment with a stiffer spring. I’m sure Britt will solve his problem in short order.

Don

[marolf101x]

To address Dons last post so everyone has a better understanding:

Spring Basics:
Each spring has a specific rate. . . in example #1 we'll use 200# spring rate for easy math. It takes 200lbs to compress the spring one inch, and another 200lbs each inch after that. In example two we'll use 400# spring rate. Meaning it takes 400lbs to compress the spring each inch.
Hyperco springs will compress to 80% free length before reaching coil bind. So a 12" spring will reach coil bind at 2.4" (so let's use 2.5").

Vehicle Info for our example:
Let's say you have a typical muscle car (how about we use the 70 camaro, grab an average weight from our vehicle weight repository, and round up for easy math? So we'll use 1600lbs rear weight.)
Since 4-link rear suspension systems typically have near 1:1 motion ratio we'll use that. . .again for easy math.
You want 5" of wheel travel for a street driven car. We use 5.2" stroke shocks in nearly all of our 4-link kits for this very reason.
Ideally you want 60% of total travel available for compression events, and 40% available for rebound (you hit more bumps than you do jump the car). So if you have 5" total travel, 3" will be used for compression, 2 inches will be used for rebound. For an easy way to see this, just make sure you have 2.5-3" of shock shaft showing at ride height.

Spring preload to reach ride height:
Example #1; 200# spring rate:
1600lbs divided by two equals 800lbs per corner, so each spring must carry 800lbs.
If it takes 200lbs to compress our spring an inch, by the numbers the spring will compress 4 inches to support the 800lbs, meaning the installed height of the spring is now 8".
****Though you can turn the adjuster nut to move the car body up and down, the actual height of the spring never changes as the weight load never changes.*****
So in our ideal situation we have 3" of compression travel. Our spring is now 8" tall. If we compress 3" so the shock bottoms out, the spring height changed to 5". . .we'll above the coil bind dimension, and perfectly fine to use in our situation.
Example #2; 400# spring r
Vehicle weight did not change, so 1600lbs divided by two equals 800lbs per corner, so each spring must carry 800lbs.
If it takes 400lbs to compress our spring an inch, by the numbers the spring will compress 2 inches to support the 800lbs, meaning the installed height of the spring is now 10".
So in our ideal situation we have 3" of compression travel. Our spring is now 10" tall. If we compress 3" so the shock bottoms out, the spring height changed to 7". . .we'll above the coil bind dimension, and perfectly fine to use in our situation. But we had 2" for rebound (droop). Installed spring height was 10", if we drop the suspension 2" we have 12". . .right at the free length of our spring. Any further and we run the chance that the spring will fall off the spring perch if we lift the car off the ground.

Both examples work. . .they hold the car up. But typically the 200# spring provides a much more supple ride quality than the 400# spring.

For ride quality a lighter spring rate with more preload will provide a better ride. . .to some extent. If you get the spring rate too light you could bottom out, resulting in worse ride quality. Let's say you hit that pothole Don is talking about. If the spring rate is too light, the force of the wheel/tire compressing the spring will "blow through" the spring rate allowing the shock to bottom, thereby transferring all that force into the chassis, and eventually your butt.

[dhutton]

For ride quality a lighter spring rate with more preload will provide a better ride. . .to some extent. If you get the spring rate too light you could bottom out, resulting in worse ride quality. Let's say you hit that pothole Don is talking about. If the spring rate is too light, the force of the wheel/tire compressing the spring will "blow through" the spring rate allowing the shock to bottom, thereby transferring all that force into the chassis, and eventually your butt.[/QUOTE]

This is what I was talking about but when I refer to preload (probably incorrectly) I mean preload on the fully extended shock. In my experience if the spring is significantly compressed when the shock is fully extended ride quality sucks. I prefer to minimize this with a stiffer spring. I find this to be a better compromise for street driving.

Looking forward to your recommendations to solve the OP’s problem.

Thanks for the detailed response,
Don

[marolf101x]

Don, you are correct, a stiffer spring would be required in your example.
Just to clarify, what happened in your example is that the spring was so light enough preload was required to cause the spring to reach coil bind before the shock bottomed out. Whatever spring rate is selected, one must make sure the compressed and extended lengths are appropriate for the application based on weight (load), installed height, spring free length, and required travel.
Make sense?

As soon as we have more info on the OP's set up I'll be able to dig a little deeper.
Just thought this was as good a place as any to quickly discuss linear rate coil springs a bit.