[Olitho]

What are the alignment specs you T1 drivers are using for track only applications of your car:

For Hoosiers?

For Kumhos?



Thanks,
Olitho
:usa: :usa: :usa:

 

[dmtnt]

I'd go -2 to -2.5 front, and no more than -1.4 rear assuming you can get that on the stock alignment hardware. Hardbar sells fixed camber plates that work well.

 

[Subdriver]

What are the alignment specs you T1 drivers are using for track only applications of your car:

For Hoosiers?

For Kumhos?



Thanks,
Olitho
:usa: :usa: :usa:

Oli,
There is not one right answer to this question, and if there was, I'm not sure if any of us T1 guys would share it online... :lol:

The answer is dependent on several things including, the track, the tire make and size, driver ability and preference, suspension components, etc.

More specific thoughts:
- Track. I optimize my alignment for each track. Early last year I bought scales, laser level, camber/caster plates, toe plates and taught myself how to align my car. I don't use the same alignment at any track. CW tracks are different from CCW tracks. Fast tracks are different from slow tracks.
- Tires. In SCCA T1 we are allowed to run 17x10 front and 17x11 rear wheels with either 275/40-17 front and 315/35-17 rear, or 315/35-17 all around, but we can go +/- 20mm on any of the above to a max of 315 width... meaning there are a lot of tire options. 275 fronts don't respond the same as 315 fronts.
- Driver. Some drivers like a car that has lots of static understeer ("tight" for circle track terminology), others like a car with some oversteer ("loose").
- Suspension. The lower the car is, the more negative camber you can get. Without T1 leaf springs, you likely won't be able to get as much negative camber as a T1 car. Additionally, the camber plates you use will impact camber in a big way. Many T1 drivers use the GM Performance Parts T1 camber plates which give max negative camber with no adjustment. Others just use the stock concentric bolts and get less camber, but adjustible. Not legal in T1, but the Hardbar camber plates are like the T1 camber plates but available in many different camber settings other than just max. A very nice product.

What you really need to do is set your alignment and go drive on it and take tire temps. Learn to read the tire temps and see what the tire is telling you. Ideally, the inside, center and outside of the tire should be within 20 degrees of each other. When taking tire temps you shouldn't do a cool down lap, and minimize the time in pit lane. You want a snapshot of the tire temp on the track and a long trip down pit lane with lots of negative camber will heat the inside and bias the results. If outside is too hot, increase negative camber. I outside is too cold, lower camber. If center is too low, try a higher pressure.

All that said, here is a rough starting point not knowing what leaf springs you have, whether your car is lowered, and assuming you have R compound tires and assuming you want a track vice auto-x alignment:
Front:
- Camber: Max negative (T1 camber plates will give about -3.0 on a T1 suspension as a data point for you), matched side to side
- Caster: Max positive, matched side to side
- Toe: Very slightly out
Rear:
- Camber: -1.0 to -1.5, matched side to side (T1 plate will give about -1.5 on my LR, but more on my RR)
- Toe: -1/8 to -1/4" in

Hope that gives you something to start with. :cheers:

 

[DJWorm]

Sub,

I'm sure you meant:

If the center tire temp is too low, try a higher pressure
If the center tire temp is too high, try a lower pressure

 

[Subdriver]

Sub,

I'm sure you meant:

If the center tire temp is too low, try a higher pressure
If the center tire temp is too high, try a lower pressure

Oops... :

Fixed, thanks for the catch. :cheers:

 

[fatbillybob]

Sub,

Are bushings open in T-1. If so you can change the front camber off max neg if you want just by making new ones. Also, If you have a probelm rr to lr in negative camber due to non-adjustable plate you may be able to make your own eccentric bushing to compensate. For 400 bucks you can buy the cheapest minilathe and then 50 bucks gets you a 10ft piece of 1.5" diameter delrin. I have cut race bushings for my purposes with great results.

Also, what is the theory for that much toe in for the rear? In midengine or rear engine porsche toe in helps resist the natural over steer and snap oversteer and we use toe-in on the rear as one tool.

Front heavy cars push more and when you do oversteer letting off gas a bit then back on tucks the rear back in right? So rear toe is for???? highspeed stability??? I'm clueless in racing front heavy cars.

 

[Subdriver]

fatbillybob,
Agree with all of what you've said... but none of it legal in SCCA T1.

We must use either stock bushings or GM Performance Parts T1 bushings which are just harder rubber. We must use either stock concentric bolts or GM Performance Parts T1 camber plates.

I'm not an expert, but am learning. My understanding of rear toe is much as you stated. With more rear toe in, the car has more static understeer, which it already has enough of to start with. But, the rear toe in counters power on oversteer allowing you to put the power down earlier or more aggressively. I've read of auto-x'ers on this forum using as much as 1/2" rear toe in.
I use less for faster tracks, more for point and shoot type tracks. :cheers:

 

[Mafia]

understeer

I read about the inherent understeer in the C5 Z06, but after taking it to the track I didn't really found there to be any. Car turned in very nicely and actually felt pretty well balanced. I'm using 275/305 Toyos and have -1.7*/-1.2* camber f/r, 0 toe f/r. Everything else is stock.

Now that whole leaf spring bisness is a different issue. On some of the bumpy corners it felt as if someone was tugging on the inside front wheel. Quite a weird feeling after driving a car with double A-arms & coil springs in each corner.

Drew

 

[fatbillybob]

fatbillybob,
But, the rear toe in counters power on oversteer allowing you to put the power down earlier or more aggressively. I've read of auto-x'ers on this forum using as much as 1/2" rear toe in.
I use less for faster tracks, more for point and shoot type tracks. :cheers:

Cool...I just learned something. Thanks for sharing.

 

[fatbillybob]

Now that whole leaf spring bisness is a different issue. On some of the bumpy corners it felt as if someone was tugging on the inside front wheel. Quite a weird feeling after driving a car with double A-arms & coil springs in each corner.

Drew

Drew,

Can you explain this? The vette leaf are tied down to the frame in such a way that by the pictures it appears that there is no crosstalk between the left and right side of the spring like you would expect in say a sway bar that intentionally talks to the over side. Am I not reading you or are you implying that there is crosstalk unlike with coilovers?

 

[DJWorm]

Rear Toe IN accopmplishes a number of things.

Under hard acceleration and cornering the rear will squat and cause the rear wheels to Toe OUT. If the wheels are set with the appropriate amount of Toe IN to start under herd acceleration they will Toe Out to Neutral.

There is cross talk across the composite spring.

When cornering with IRS, Rear Toe IN allows the wheels to follow and track the turn better......ie the car will turn easier and quicker with less understeer.

 

[ghoffman]

Another thing is you cannot use a delrin bushing that is configured in a cylindrical bushing on a C5. That would work on the uppers but both front and rear lower a-arms need either a compliant bushing (i.e. rubber or urethane) or a spherical bushing because of the way the pivots are not both co-axial and parallel due to the way the car is aglined.

 

[Mafia]

Drew,

Can you explain this? The vette leaf are tied down to the frame in such a way that by the pictures it appears that there is no crosstalk between the left and right side of the spring like you would expect in say a sway bar that intentionally talks to the over side. Am I not reading you or are you implying that there is crosstalk unlike with coilovers?

It definitely felt like crosstalk, but only under 3 conditions:

* bumpy corner
* sticky tires
* decent speed

It wasn't bad in a sense of upsetting the car, it was just an odd feeling. Car is fast, no doubt - it just gets there in a different way than most modern performance cars.

 

[WhosUrDaddy]

It definitely felt like crosstalk, but only under 3 conditions:

* bumpy corner
* sticky tires
* decent speed

It wasn't bad in a sense of upsetting the car, it was just an odd feeling. Car is fast, no doubt - it just gets there in a different way than most modern performance cars.

Agree with that. Compared to my '01 M5, the Z gets it done via its relatively low weight, low ride height and wide stance. The Z has a penchant for getting upset at high speed under high G's as well as willingness to rotate (some is good, too much is scary). This is similar to Viper's I've driven on a track.

In contrast, my M5 and 911 (German) track experiences have given me earlier confidence at the limit. My ability to trail brake easily in an M5 vs "no trail braking allowed" in my Z is evidence.

I'm guessing that a Z "REALLY" would benefit from a coilover set up but likely won't spend the dough.