fatbillybob

This is an FYI thread hopefully to save you guys some money. It is about rear bumpsteer for C5 Vette stock T1 race suspension. Conclusion NO bumpsteer kit is needed. GM did a great job.

People talk about bumpsteer. Guys make bumpsteer kits. People think stock suspensions need bumpsteer correction. I searched and no one has measured it. I measured it. I did the laser and mirror method.

fatbillybob

Here is my bumpsteer trace. It shows full compression and full droop. You want the minimal horizontal trace on the X-axis.

fatbillybob

My math turned out to be 0.15 degrees of bump travel
I set my rear toe to 1/8" rear toe which comes out to 0.275 degrees.
Most people set rear toe in inches. An alignment shop would use degrees because they have a machine.

This means:
Bump travel causes the suspension to swing from 0.125 to 0.425 degrees which translates to approximately 0.028" to 0.10"
That means if you set your toe in to 1/8" total toe your max bump travel is near zero toe to less than 1/4" toe total toe. That's pretty insignificant. The math implies no bumpsteer correction needed I guess. I do not think I could correct closer than 0.15 degrees. I have a bump kit in the garage but I'm not even going to open it and try to get any closer. If I'm wrong I'm happy to learn.

KnightDriveTV

That's pretty awesome info, definitely insignificant. I was going to get the rear kit shortly, just simply to eliminate any deflection under big throttle inputs, maybe I'll just focus on bushings out back.

sccaGT1racer

The correct way to measure bumpsteer is set vehicle suspension at ride height. Take a zero measurement then measure at 1 and 2 inch of compression then 1 inch of rebound from ride height. I always try to get under .050 or less of an inch per wheel.

Sox-Fan

Thank you for doing this.

Would it be fair to infer that a C6z is the same, or no?

crimlwC6

Thanks for the effort. I was going to install/make a bump steer kit just to use heim joint to reduce replacement intervals. I've never felt the car do something significant that I would associate with bump steer.

fatbillybob

From the pivot point of your guage to the tip of your dial gauge what is the distance? I would like to compare what 0.050" is to degrees.


And yes started at rideheight so you know the compression and rebound range for total bump.

fatbillybob

I do not know but I have always though of the C6 as really C5 2.0. The C7 has extra caster stuff to adjust in the rear we don't have. When people talk about C5 C6 that is never mentioned. Also they share a lot of the same suspension parts. So my WAG is yeah they are the same.

93ASP

C6Z is definitely not the same as the C5 for rear bump steer... C6Z as set from the factory has significant toe in in bump where the C5 (at least with the rear camber settings that I ran) had toe out in bump.

sccaGT1racer