[iburke]

After coming back from my first road course experience at Spring Mountain. I find my rear tires are worn more on the outside 1/2 than the inside. about 1 or 2/32's difference. Is this normal, do I have an alignment problem, or is tire pressure incorrect for the track? I had a 4 wheel alignment before we went, and I was running about 38 lbs pressure cold.

This stuff is a lot different than 1/4 mile raceing...

 

[iburke]

Any one out there track your vettes? Other than us newbes

 

[wburke]

:huh:

 

[AaronPfadt]

Ivan,

That is normal. The issue is that under track conditions, the car has body roll (a lot the way you drive :laughing and that roll angles the outside wheel out at the top. In effect it gives you car some positive camber, which is not only bad for tire wear, but for grip as well. With positive camber, the tire is riding on the outside half.

Your stock Z06 alignment is good for moderate street driving and long tire wear. If you are going to hit the track with the car, it is advisable to get a more 'aggressive' alignment. Essentially, you add negative camber to the wheels (tip the top in) to counteract the positive camber you get from cornering. Tire flex also plays a roll in the wear patterns you see, but it is easiest to think about in terms of camber.

The downside to this added camber is that you will wear the inside edges of the tires more than the outside during street driving. The alignment of a car that is used for track and street use is always a compromise.

Here is my basic C5/C6 track setup. For street tires and moderately stiff suspension (Z06, Z51, Pfadt coil overs, T1 etc...).

Front Camber: -1.3 to -1.5 deg
Rear Camber: -.1.0 to -1.2 deg

Toe: straight in front and rear

This will work nicely at the track and on the street. It isn't optimum for either. We used approximately those settings on the C6Z we ran in the One Lap of America and had good tire wear over 8 track days and 4500 miles of driving. We were starting to wipe out the outer edges of the rear tires due to not quite enough negative camber (we were at -.9 in the rear). We were on street tires and didn't want to compromise straight line acceleration too much (over 600 hp). The more negative camber you put in, the less grip you get when the car is going straight. There are always tradeoffs.

Hope this helps. So just add a little more negative camber and that will even out your wear some and add grip for the next time you head to the track. You should definitely head down to Hallet in Tulsa. It is a really cool track. I think you would like it a lot.

good luck,
Aaron

 

[Dan85Vette]

Dang that's some great info Aaron!

the car has body roll (a lot the way you drive :laughing

Yea you about covered it there, I still wake up in the morning with my head tilted at a 45* angle.

 

[iburke]

Thanks Aaron I was hoping some one out there knew what I was asking.

Hey Dan the next time we will drive back wards that should get your head on straight...

So my best bet would have the alignment reset befor I go to the track...and then set it back after I'm back..

 

[RKT ROY]

Welcome to road course racing

Ivan,
Welcome to running on tracks where you have to use your brakes and turn. As Aaron says, wearing out the outside of your tires is normal with this kind of driving. I've always been wearing out the outside shoulders of my tires even at the max factory camber settings. So I just installed a set of Aaron's camber plates. I went with a pretty agressive setting of -1.75 in front and -1.5 in the back (had to use the 6 notch plates in back). I'm headed to the Streets of Willow Springs tomorrow morning for a track event and I'll see how much better my grip is and what my wear pattern is.:thumbsup:
Have fun!
Roy.

 

[iburke]

Ivan,
Welcome to running on tracks where you have to use your brakes and turn. As Aaron says, wearing out the outside of your tires is normal with this kind of driving. I've always been wearing out the outside shoulders of my tires even at the max factory camber settings. So I just installed a set of Aaron's camber plates. I went with a pretty agressive setting of -1.75 in front and -1.5 in the back (had to use the 6 notch plates in back). I'm headed to the Streets of Willow Springs tomorrow morning for a track event and I'll see how much better my grip is and what my wear pattern is.:thumbsup:
Have fun!
Roy.

Hey let us know how it works out Roy. This bug has me bad. I have one of Aarons Chassis Stiffening Bars on the way. Picking up a K&N 63 Series Aircharger Kits Tuesday. All I need now is some time off from work and my business so I can go wear out some rubber...:laughing:

 

[bahnzii]

Ivan,
Welcome to running on tracks where you have to use your brakes and turn. As Aaron says, wearing out the outside of your tires is normal with this kind of driving. I've always been wearing out the outside shoulders of my tires even at the max factory camber settings. So I just installed a set of Aaron's camber plates. I went with a pretty agressive setting of -1.75 in front and -1.5 in the back (had to use the 6 notch plates in back). I'm headed to the Streets of Willow Springs tomorrow morning for a track event and I'll see how much better my grip is and what my wear pattern is.:thumbsup:
Have fun!
Roy.

Let us know how you like Streets of Willow. I have always wanted to run there :thumbsup:
Oh and post some data from your driftbox when you have a chance, I am seriously thinking of getting there road race version:
http://vboxusa.com/performancedrift/

Ivan, I am so with you - after Spring Mtn, I have the road racing bug BAD!!!

 

[RKT ROY]

So my best bet would have the alignment reset befor I go to the track...and then set it back after I'm back..

Ivan,
You should just get Aaron's camber plates and set up for an agressive camber and leave it that way. Just do more track driving to even out your wear!:laughing:

Here is what my right front tire looked like after Streets of Willow yesterday (after 8 track days, I have replacements waiting in the shed):

This is what the Pilot Sport Cups look like when new:

Here is my right rear tire after 6 days (good for one more weekend). I rotate my tires around after each track day to even out my wear, so my left tires look much the same as the right tires.

The Streets of Willow is a fun track, hard on brakes and tires, plus I saw oil temps up to 298 degrees. I have a Lingenfelter oil cooler on order. This track rewards handling so light nimble cars do very well (Corvette horsepower is not a big advantage here).
The Pfadt camber plates really helped with tire wear (believe it or not). I was able to nurse that front right tire through the day, which surprised me. I did notice that with the rear camber, I had a little more trouble getting the power down at the exit of the corners.

P.S. Ivan, This is why the outer shoulders wear out. At Buttonwillow my right rear was lifting a little. You can see an orange cone in the daylight under my tire:

 

[bahnzii]

Nice!!

That last shot where you can see some daylight under your right rear is sweet :thumbsup:

You mentioned rotating, I gather the Cups are not directional, just asymetric?

 

[Patrick]

Great pics Roy!!!

 

[iburke]

Thanks for the info and a great picture Roy...:thumbsup: