Road Racing Suspension Set Up Trouble
 

Hey guys,

I am having problems setting up our 82' rx7 w/ a 85' GSL rear end (disc brakes) suspension. We have 150lb front springs and the rear springs I believe 300lbs.From what we have learned on track and from reading on the internet, our rear springs are too heavy. We do not have a panhard bar or watts link. We are trying to figure out where our handling problem is initiating, because it is absolutely the hardest car on the planet to drive!!!

The symptoms: The car vibrates terrible on right hand turns (from what I read on here, it is the skipping effect of the front tires). Is there an obvious low cost fix to eliminating this "skipping?" The car is lowered and I think maybe raising the whole car a bit will help??? Left hand turns are a million times better than right, as we can run with miata's through the lefts. It also feels like the car is binding its self up really bad and then just snaps loose. There is no warning except for a humming sound while in the corner (the sound is louder the harder you are going). It is a very sudden snap and is very hard to gather up.

I thought that maybe the axles could be bending a little with the bigger wheels, or maybe the brake calipers are laying over into the rotor, but there are no real signs of that, so that is why we think suspension.

One more thing: We have 15x7 diamond racing wheels (which we didn't know needed balanced when we bought them)


Sorry for such a long post/question, but we are not sure where to begin on solving the problem.

I really appreciate any feedback and help on this.

Thanks a lot!!

You need either a Watts link or panhard bar. Without either the rear end would be shifting back and forth. Your spring rates are backwards. Our Pro7 car had 350 fronts and 150 175 rears (i don't remember). That being said, if your wheels are not hubcentric, it may cause an issue when loaded if not centered properly. Or a flat spotted tire. Or a blown shock on the left front.

Thats where i would start. And figure out what is centering your rear axle...

I appreciate it!

I run 275 front/150 rear springs on my autocrosser. I use Respeed's coilovers (front) and adjustable perches (rear). Front shocks are Illuminas (actually MR2 rears) and the rears are short bodied Bilsteins. Front Respeed hollow swaybar and a 3 position rear bar. Camber plates also from Respeed.

With all of that, I can set the car up for anything. I've had a tri-link/panhard setup sitting on a shelf in my garage for several years now, but never saw a need to install it. The car is just plain "happy" just how it is.

As I mentioned, I autocross her on a regular basis. I also driver her down South on a fairly regular basis, often putting in well over 2k miles in a week. I've had her to racetracks at Atlanta, and a couple of local tracks.

Now, with all of that being said, based on your description you are suffering from the dreaded "snap oversteer". This happens when the rear of the car rolls to the point that the suspensions binds. There are many ways to address this, such as the tri-link/panhard setup. I addressed it by reducing the amount of movement in the rear end. With good shocks, the right springs, and a lower ride height, my car corners very flat. There is nearly no roll at all. As I said, this has worked so well that I seriously doubt that I'll ever bother with the tri-link install.

I hope this helps. :)



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I could use the tri link set up

Thanks for the input! Now i need to find some Illuminas