whosurdaddy

There is much material on this forum about alignment spec's, though I'd like to confirm my thoughts for my C6 Z06 with you guys who generally know way more than I do.

I am an intermediate/advanced driver running 2.14's at VIR Full, 2.13's Watkins Glen and 1.21's at Summit Point (re-paved) Raceway. I run with PS2's and track pads - currently Carbotech XP8's because 10's overpower the street rubber.

The current alignment is:
- Lowered to the bottom of stock bolts
- Front -1.7* camber, Max Caster, 0* Toe
- Rear -1.2* camber, 3* Toe In

- While my rears tires are fairly new 345's, my fronts are 1/2 done 295's.
- I drive my car a good bit on the street, though its still a 3rd car.

I'd like to dial out some understeer, while I realize I'll be living with some as my fronts are a bit older. I recently looked at video of David Farmer driving his Z06 around VIR, and compared his 2.11 lap side by side one of my 2.14's. I did notice that he puts in less steering input at some of the places I am most unhappy with understeer (T1 & T5 for example).

I am sure that some of this is skill (syncronization of steering input with throttle & brake), but I'm also betting that some of it is set up related.

So I am thinking that its time to put some Toe Out up front. Any recommendations to my current setup? How many degrees of Toe Out do I go for? I hear 1/8" per wheel, but don't know what that translates to in degrees.

Thanks in advance for suggestions and commentary.

WNDOPDLR

Why not contact David and have him set up your car. I think it is dirt cheap for the job he does.

Solofast

Chasing setup with known bad tires is a really bad idea. Get proper tires on all four corners and then work your setup. If you start dorking with the setup to get the car balanced on bad tires, then when you get good tires on the front you are going to be looking out the side windows at where you are going. You will likely spend a full day getting it back to right. Stretching tires like you are doing is a false economy.

The toe change will only help on turn in, not address the understeer issue. You are shy a bit on front negative camber, and that is more likey why you have some push (in addition to the tires). Suggest -2 degrees in the front for serious track work (and if you are looking at times then you are getting serious).

Also you can soften the front bar with a alignment shim between the frame and the sway bar bracket (assuming that you still have front rubber bushings in there). That is a relatively minor change in front roll stiffness and if you just have a little bit of push after you address the tires and front camber issue (not likely) you can go back to bar stiffness.

TedDBere

Some of the C6 Z06 guys I've spoken with have had a hard time getting a good balanced car with the stock sway bars. Either the car pushes a little when the back is planted or the back gets loose when the front is planted. They seem to think the rear bar needs to be stiffened a tad. FWIW. Good luck.

whosurdaddy

Interesting tidbit on the shim for the front sway bar. How does a shim soften it?

Also, I'm not so much stretching my fronts as I am using them for their useful life. They've got about 6 track days left on them from what I can tell. I just can't keep the fronts and the rears syncronized - the rears go faster ........... no idea why?????

C6400hp

One if you are lowered all the way on stock bolts, you are probably too low.

Two, 3* toe in back seems a bit extreme. I have less than .10 in on back.

I would raise all the height adjustments to the lower end of the recommended spec.

Go to something like .15 toe in on back and .10 toe out on front.

davidfarmer

if you are a low as you can go symetrically on the stock adjusters, you are fine. Ours is all the way down, and it isn't low at all compared to some of the C5's I see. You could always add more camber in the front, but since your rear is pretty conservative, I wouldn't think you'd need it.

I would suggest a little toe out in the front, 1/16" or so (.2deg) and slow down the hands. I really try to be as efficient as possible in the turns, and use the least steering input that will keep me on the track.

I wish I had some better video for you, as the Z06 will do 2:04's pretty easily on a clear track. The NCM video was a balance of old tire, running on brake backing plates, and now we've developed an engine miss to boot.

Solofast

The bars these cars are stiff relative to the bushings. The total sway bar spring rate is the rate of the bar AND the bushings, so softening the bushings will result in less front roll stiffness. It doesn't take much since the bars are so stiff, there is a good bit of motion in the bushings. If you reduce the preload a bit you are doing the same thing as softening the bar. If you go too loose (more than a couple of 1/16th of an inch shims) you will be in trouble, but taking a little bit of preload out can "fine tune" the front bar. Just like putting in poly bushings can result in more front stiffness, softening the bushings does the same thing in reverse.

I put a set of studs into the frame and put a washer and a nylock nut to do the clamping. I can dive under the car between autocross runs and crank in a half a turn + or - to dial in the car to the surface....