Alludc

EDIT 2-20-12 im readdressing this alignment. Although I am very happy with this, I have since changed out my shocks and tonite I plan to play around with the ride height a little so Ill be going back in for an adjustment to the above. I am currently autoxing the car on rs3s, and the car goes back on Firestones for daily driving which is only approx 6-8k miles a yr max.

What would you change for the BEST street tire autox performance?



went to an alignment shop today after doing a bit of a drop earlier in the week.
99 FRC on z06 size wheels/tires.
Dropped to 27" front 28" rear. Thats from the ground thru the center of the wheel to the fenderlip (yes I know I should measure to pucks).

Alignment sheet...




very well known local alignment guy. he gets a ton of the drift crowd, autox guys, lowered cars, etc. Asked him his opinions on a street car (that gets about 5-8k miles a yr) that I drive the way it was meant to be driven, and will autox a time or two a month if I can. I wanted agressive street settings and what I got is whats above. Im not so good at reading it though so I value your opinions.

ErnieN85

Alludc

I'll take that as " I got what I asked for? "

ErnieN85

sure did just about what I ran on My Z06

Z06trackman

A couple of comments:
Most folks tracking or autocrssing their cars use between 1.5 and 2X more chamber in fornt than in the rear.
3/8" total toe in the rear is a ton! I think you will seriously wear the insides on the street, and you don't need anywhere near that much. 3/16" total on the rear should be plenty even for autocross. I have found 1/16" good for my driving style on the street. You can adjust this yourself easily with a tape measure, a helper, and some practice.

Alludc

the results at the track were most definitly promising! Huge improvement

As far as the rear toe does anyone else concur with z06 trackman. Although I dont drive a lot on the street, id hate to have significant wear when I do as that was not my intention.

J.R.

3/8" toe in is quite a bit.

Even on a full track car I do not run that much.

Below is a general guide that Pfadt Racing provides:
Pfadt Corvette Alignment Recommendations
These settings are a guide based on the experience and testing of Pfadt Race Engineering. Toe specs listed in inches are intended to be measured using a toe plate with approximately 21-5/8" between notches for tape measures. Negative toe measurements indicate toe-in.
Performance Street
Performance Street - Track Use with Street Tires
Performance Street - Track Use with Race Tires
Dedicated Track Car - DOT Tires, poly bushings
Dedicated Track Car - DOT Tires, Spherical Bearings
Dedicated Track Car - Race Slicks, Spherical Bearings
Front
min
-0.7 7.5 -1/16" (0.17°)
-0.4 -1/16" (0.17°)
max
-0.9 8.5 0 (0°)
-0.6 0 (0°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings will provide good performance and good tire wear
Front
min
-1.1 7.5 -1/16" (0.17°)
-0.7 -1/8" (0.33°)
max
-1.3 8.5 0 (0°)
-0.9 -1/16" (0.17°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings will provide good all around performance. The tires will wear the inside edges in street use and the outside edges on the race track. This is a good dual purpose alignment.
Front
min
-1.6 7.5 -1/16" (0.17°)
-0.9 -1/8" (0.33°)
max
-1.8 8.5 0 (0°)
-1.1 -1/16" (0.17°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings will provide great track performance. The tires will wear the inside edges in street use, and the car may tend to grab the lanes of the road. Race tires will wear well at the track and provide high levels of grip. This alignment is compromised towards track use.
Front
min
-2.8 6.5 -1/16" (0.17°)
-1.5 -1/8" (0.33°)
max
-3.0 7.5 0 (0°)
-1.7 -1/16" (0.17°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings are a good starting point for a car with polyurethane or stock control arm bushings. This alignment requires DOT race tires to function appropriately. This is a starting point only, testing and monitoring tire temperatures and pressures are required to optimize any setup.
Front
min
-2.4 6.5 -1/16" (0.17°)
-1.2 -3/16" (0.50°)
max
-2.6 7.5 0 (0°)
-1.4 -1/8" (0.33°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings are a good starting point for a car with mono-ball or spherical control arm bushings. This alignment requires DOT race tires to function appropriately. This is a starting point only, testing and monitoring tire temperatures and pressures are required to optimize any setup.
Front
min
-3.0 6.5 -1/16" (0.17°)
-2.0 -3/16" (0.50°)
max
-3.2 7.5 0 (0°)
-2.3 -1/8" (0.33°)
Rear
Camber (deg) Caster (deg) Total Toe
Camber (deg) Total Toe
Notes
These settings are a good starting point for a car with mono-ball or spherical control arm bushings. This alignment is designed and tested with race slicks, not DOT tires. This is a starting point only, testing and monitoring tire temperatures and pressures are required to optimize any setup.

Pfadt Racing

Looks like you ended up with a little more rear toe than we would like. The car probably feels much better because you actually got some camber put into the system while Zeroing out the toe in the front. We've found that a little bit of Toe In really does stabilize the car at high speeds.

You may want to take it to a qualified race shop in the area and have them take a look at it. Try contacting your local SCCA or NASA region as there may be another option in your area. Overall the alignment doesn't look awful like it did when it went in, but it may be worth keeping a close eye out on rear tire wear:

Thanks for the post JR. Here is a copy of our alignment guide in a form that's a bit easier to read. You can print this guide and have your guy set the car up to our specs: Pfadt Race Engineering Alignment Guide

Alludc

right on. thx all

acrace

Since in another thread you had questions about A-Stock autocrossing, here are some thoughts from an autocross perspective on your alignment.

For front camber, most folks at the National level run between -2.0 to -2.5 deg. Some of the top guys run more negative camber for more cornering grip, while another group believes that going much over -2.0 affects braking performance.

With zero toe, I would suggest marking the toe links. It becomes really easy then to adjust front toe to see what you like. Many autocrossers will run a touch of toe-out to enhance turn-in characteristics.

With the factory bars, I ran a ton of rear toe-in. I ran a touch more than 3/16" per side on my C5 Z06. I'm not the best at throttle modulation and there is a ton of deflection in the rear. When I went to a larger front bar, I was able to go to a touch less than 1/8" per side. I'd suggest marking the rear links and playing with the adjustment and see what works for you.

For rear camber, if you're autocrossing in Stock category trim, you're going to be limited to what's in the car. Most folks with a C5 are in the -1.2 to -1.4 deg range.

Note - my comments are for a car used primarily for autocrossing and running the sticky DOT R-compounds (Hoosier A6s in my case).

acrace

By the way, I should mention that some of the top folks in the autocrossing sport also play with rake as a way to adjust the understeer/oversteer balance, although I haven't really fiddled in that arena.

Alludc

im readdressing this alignment. Although I am very happy with this, I have since changed out my shocks and tonite I plan to play around with the ride height a little so Ill be going back in for an adjustment to the above. I am currently autoxing the car on rs3s, and the car goes back on Firestones for daily driving which is only approx 6-8k miles a yr max.

What would you change for the BEST street tire autox performance?

Solofast

You are really into unknown territory with street tires. Most folks running serious alignments are running DoT rubber.

What you need to do is take the car to a test session and measure tire temps across the tread, inner, mid and outer, and tune your camber and tires pressures accordingly.

With more negative camber, you can run lower pressures, which increases footprint and grip, and also gets your tires hotter, faster, both of which are important to you.

Shoot for even temps and adjust accordingly. Camber will effect the inside and outside relative to the middle, and higher pressure will lower the temp in the middle of the tire and also will increase rollover to increase the outside temp...

Since ST class tires are pretty darn good, you probably should be starting somewhere near -2 in the front and -1.5 in the back anyway.

Post what you ended up with for camber and pressures...

Alludc

I was considering bumping the camber .5 f/r from where it is now as I realized it would be hard to find a real solid answer on this relatively unknown situation. Will do on the temps, hopefully this wkd.

sperkins

Was race weight simulated? If not, the rear will toe out when you're in the car. I run at least that much rear toe and don't have bad wear issues.

Alludc

race weight wasnt simulated, and with my weight in the car its distributed like so... 113lbs goes to the left rear, 47 to the right rear and the rest is pushed up front.

I have not noticed any significant wear on the inside rears on my dd tires, or my hankooks.

justkickin

It will take quite a few miles to see differences in wear.

I would be inclined to dial in more front camber, and dial out some rear toe, even on streets.

Toe is going to cause more tire wear than camber, not that camber won't cause any on the street. By reducing to, you will decrease wear but you will need to modulate throttle more.

With all that caster you may not need toe up front. See how turn in feels at the next event and go from there.

Gordy M

The last 8 years I have had a C5 FRC and I agree with Al on the Hoosier set up for autocrossing and for HPDE/TT I used a little less rear toe. For autocrossing on street tires I found -1.8 front camber and 1/16 toe out and balance the caster as High as I could. The rears are -1.0 camber (thats the max I can get in the rear after moving the cradle) with 1/8 toe in. I haven't run HPDE/TT on street tires in 7 years and can't remember what I set them at.

After you finalize on a new alignment you will also need to do some testing for tire pressures. I found street tires have a wider variation in temp settings than Hoosiers when I made alignment changes.