Thanks for your help guys, I've got the handling problem cured ... and of course, the problem was in my own making.

I had recently installed a 02 ZO6 suspension set up and then was unable to get the car to turn in or corner neurally. During the suspension work I had alot of trouble with putting in the poly control arm bushings and had given up after putting in the front ones. Of course you wouldn't expect that merely stiffer control arm bushings would cause understeer ... and they didn't ... but what I had neglected to tell you all was that I had also installed poly bushings on the front sway bar mount and not the rear. I evened up the bushing material front to rear and the car drove great. (I guess these things really do stiffen up the bar!)

I spent several hours fine adjusting with a theromocouple on a skid pad and I think I have a very good track set up for a C5 coupe, FE4 springs/bars, Bilstein sports, 275 + 315 R3SO3 hoosiers and still within the adjustability of the stock a-arms. (not T1 a-arms)

This came out to be: front 1.5 negative camber; toe 0
rear .70 negative camber; toe-in 1/8th inch

Sorry about overlooking the bushings:"Duho". Krusty seemed the closest to getting it right on! I hope that my pain was instructional. sj

 

Carroll Smith has a warning in "Tune to Win" concerning suspension setup on the skid pan.

A car setup on the skid pan for neural handling, will immediately go into oversteer when power is applied in a real turn accelerating away from the apex.

Don't be taken by surprise!

 

Mitch:

Thanks for your reminder. I was able to adjust the car to just a hint of understeer at neutral throttle. It had some mild throttle off oversteer as well as some mild throttle on oversteer ... not enough to snap you around ... but rather just enough to get the car to rotate a little.

The testing session did demonstrate to me that the C5 suspension can be effectively adjusted within the stock settings to change the handling charactaristics.

The biggest factor was the sway bar material. The poly really stiffened up the bar noticably. Perhaps one could use this to selectively induce more under/oversteer if, for exhample, you were to radically altered the tire demensions.

Increasing the rear rake (as suggested by the Forum) from nearly flat to 1/2 inch higher in back really did cause the car to pitch a little when getting off the throttle, and did predictably started the car to rotate, nicely without any real snap.

Adjusting the front toe-in from 1/8 inch to zero made the car very happy to turn in (but, of course it will be hunting on the straights).

I'll report back after the track day this weekend. It should be a sloppy wet on Saturday as a winter storm is on it's way to Oregon. It looks like I'll be mounting up my rains. At least when its a wet track you aren't going as fast when you spin!

I'll report back to the Forum if my suspension settings are bogus, misdirected or otherwise evil. sj

 

Speedjohnson,
you mentioned that you were experimenting with toe settings. We like zero to 1/16 total toe in on the front too. Have you ever tired zero to 1/8 total toe out on the rear? It works for us :yesnod:

 

What does rear toe out feel/ drive like? Does it turn in better? is it "whippy" on the straights? What about under acceleration? thx sj

 

:confused: