In running Sebring and similar tracks, does anyone out here with experience road racing have a suggestion on cold air pressure, front and rear, for road racing?
31F/28R...but it really depends on how much camber you run and what the tire temps are where you go from there.
I also strongly suggest that you invest in some race wheels like CCW or Kodiak and shod them with either DOT Hoosiers or Kuhmos or some R Goodyears rather than wearing out expensive OEM tires that are sub par performers on the track, and risking damaging an OEM wheel when you could be running with stronger and lighter wheels.
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I have some Hoosier slicks on Stock Z06 rims that came with the car, but I didn't want to run them because the wife and I were splitting time in the car and she isn't ready for a slick yet.
You say that you can wreck the rim, how would that happen?
Not a stock Z06 wheel, but this should demonstrate what DJ was talking about. This may be an extreme case and you and your wife may not use the car nearly has hard as the car in this case was: BROKEN RIM - Texas World Speedway
I used the stock tires on the track a few times and was going to say something like 31-32F, 28-30R. At least a couple lbs higher in the front than the rear. Check them hot and see how they are doing. Somewhere around 40 hot is about right if you are driving hard. If you check them hot and let out a pound or so, the cold temps will have to be adjusted accordingly. As a note, depending on how far apart your sessions are, you can't assume they will have fully cooled between sessions so I wouldn't bleed them again.
Example, you set them 31F, 28R cold.
Hot they come out to 41F, 39R. Pretty good.
You check them 30 minutes later right before you go out and they are 35F, 33R. If you bleed them down to 31F, 28R they will be too low as they are still warm and won't heat up as much as they did the first time. My guess would be you would only get them up to about 37F, 35R in this case.
Jesus, I have never seen a rim come apart like that. I surmise that most of the posts there were accurate. The rims were aftermarket copies, which are always questionable, and were used, so noone knows the history. I am hoping that the Z06 stock rims will never have that happen. We do not run the car terribly hard, but if the wheel gets tossed, Chevy is going to hear from me.
Thanks for the air pressure thoughts, I know exactly what you are talking about.
I am hoping that the Z06 stock rims will never have that happen.
I haven't heard of Z06 stock rims breaking under normal use (i.e. excluding off roading adventures ), however the reproduction chrome Z06 wheels have failed numerous times on the track. Wheel hub fractures usually. I saw a Z06 with chrome repos break a wheel when I was at Willow Springs - did a bit of damage to the underbody, exhaust, and quarter panel.
BTW, Subdriver's recommendations on tire pressure is perfect.
__________________ '02 Z06 , Electron Blue, Vortex intake, Magnaflow X-pipe, Corsa Indy, Stainless Works LT headers, LS1 Edit, TB bypass, Hurst, MGW Gripper, Born 2/20/02 380 rwhp / 363 rwtq
I have personally seen 2 catastrophic wheel hub failures of OEM Z06 rims, one was a forged '01 and the other a spun cast '02. One was on a road course the other was during a National Tour AutoX. Both road course and AutoX induce high side loads, something that these wheels were not really engineered for. Note that even though streets can be much rougher the side loads are not as great.
In addition I have seen a number of OEM wheels damaged
1. cosmeticly,
2. enough to need repair and
3. beyond repair
from off course excursions ("failure to negotiate") and even from flat tires on a road course.
That is the reason(s) I highly recommend NOT using them for road course work or AutoX with one exception.
1. Why not save the expensive HP street tires and OEM wheels for the street?
2. Why not use lighter and stronger and sometimes cheaper race wheels for the track?
3. 3 piece race wheels are more easily repaired such as changing out a damaged half barrel only, for instance.
The only exception is that I keep my OEM wheels with the GY F1 SC's as back up Intermediate rain tires. The GY F1 SC's actually function quite well on a damp track with NO standing water. In this situation you are driving at 85-90% and are not experiencing the excessive side loads.
So what are the recommendatins for good, lightweight, strong race wheels? Of the things I don't want to happen, breaking a wheel in turn 17 at Sebring at big speed is right up there with the best of them.
Most SCCA T1 cars use CCWs, who I believe is a supporting vendor. John at CCW is extremely knowledgable about proper offsets, etc. I have two sets of 17x10 front, 17x11 rear CCWs which are the required size for SCCA T1.
Kodiak is also a popular choice, but the front Kodiak wheels require longer than stock studs which is sort of a pain...
I recommend CCW's, Kodiak wheels or Circle Wheels as a first choice,
Jongbloeds are the next step up with Magnesium centers and anodized and heat treated Aluminum rims
If you want to spend a lot of money for even lighter wheels the OZ's or BBS are top of the line. You can get these in Magnesium centers in either 5 lug or single center lug.
I disagree with your statement that your wife is not ready for slicks. In my experience I believe that it is best to learn on slicks. Once they are warmed up they offer more grip and better stability than a street tire. The problem with using street tires on the track is that the learning curve needs to start all over again when you switch to slicks. Novice drivers come up to speed much faster when starting out on just slicks.
I recommend CCW's, Kodiak wheels or Circle Wheels as a first choice,
Jongbloeds are the next step up with Magnesium centers and anodized and heat treated Aluminum rims
If you want to spend a lot of money for even lighter wheels the OZ's or BBS are top of the line. You can get these in Magnesium centers in either 5 lug or single center lug.
I disagree with your statement that your wife is not ready for slicks. In my experience I believe that it is best to learn on slicks. Once they are warmed up they offer more grip and better stability than a street tire. The problem with using street tires on the track is that the learning curve needs to start all over again when you switch to slicks. Novice drivers come up to speed much faster when starting out on just slicks.
One caveat--slicks typically give very little notice when they break away; street tires squeal and give you some notice before letting go. Some novices find that reassuring.
I went CCW's and did 18x10.5 front and 18x11.5 rear shod with Nitto 555R2's 285 front 305 rear (Street driven)
The change to 18" front made a big difference (to me) in how the car responds to steering input. Much more immediate turn in, and with the increased grip from the sticky rubber she does not understeer.
I strongly believe that any wheel that is not "formed" to final shape (forged or spun) has no buisness being on my vette period.
Castings are so much more susceptable to fatigue and catastrophic failure that It's not worth the risk to me. And I run my Excursion on Forged rims as well.
By the way, I cannot find any links or info on the CCW's, and I searched the site for a bit. Any help please? What is a set of 4 going to run? How much are 4 stock Z06 rims in perfect shape likely to bring?
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), however the reproduction chrome Z06 wheels have failed numerous times on the track. Wheel hub fractures usually. I saw a Z06 with chrome repos break a wheel when I was at Willow Springs - did a bit of damage to the underbody, exhaust, and quarter panel.
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