Working for the Dark side...!!!!

[Manny]

The factory C5 (and I think C6 as well) bushings aren't really up to the task of tracking a ~3100lb street car on decent rubber (you get alignment shifts). They might be ok on a ~2300lb GTM, but I'd think an upgrade to VB&P's poly-graphite bushings would in order for any GTM build.

I agree that the control arm bushings on the C5/6 are most certainly a weak point (don't ask how I know, been there done that). On the upper control arms they shift so that the arm extrudes toward the front of the car and on the rear they allow the lower arm to go aft. Also agree that the T1 bushings (you have to buy the control arms, they don't sell bushings separately) are better and typically solve that issue. If anybody out there is using C5 control arms it is something that needs to be fixed if you are doing serious track work or you will end up losing caster and grip... For a street car it's probably not much of an issue, but sticky tires really exacerbate the problem.

If you are designing your own mounting, you can turn around the upper rear bushing and readjust your mounting points and if it is installed backwards it won't shift.

 

[Grant]

Another thing that is strange is the front upper arm mounts are turned 90deg from stock and make suspension adjustments almost impossible without making a slot , this then required the nut and bolt clamping force to do all the work..and maintainalignment.... not ideal in the least.

I looked at that for a while... and couldn't figure out why they would design it like that?? It didn't look very strong either, although I'm not much of a ME. On the stock C5 of course the suspension adjustment is done via the lower control arm, although some people shim the upper arm mounting points for additional adjustment.

While I am bitching about the GTM, I didn't like the idea of placing stock C5 gas tanks right next to the exhaust manifolds (though I'm not really sure I've seen where the SL-C's are), nor the nearly zero clearance between the front of the motor and the firewall (any maintenance seemed like it would require pulling the whole thing).