[midnight1ss]

I did an autocross event this past weekend and I lowered the psi on my tires a bit too much which cost me some time.

I am running the stock 1LE supercar 3 tires.

Question for you guys.. what tire pressure are you running?

[Callaway SC630]

Autocross is rarely, if ever, just an outright stab of the pedal. Trying to stay away from tire roll, 35 to 37 rear and 40 to 42 front.

Check the tires scrub line after a couple of runs and see if you need to adjust.

[midnight1ss]

Originally Posted by Callaway SC630

Autocross is rarely, if ever, just an outright stab of the pedal. Trying to stay away from tire roll, 35 to 37 rear and 40 to 42 front.

Check the tires scrub line after a couple of runs and see if you need to adjust.

Wow! That’s higher than I thought! Do you spin? I see you have a callaway camaro but I’m curious lol

[Callaway SC630]

No spinning. It is about maintaining momentum. People that go into a turn too hard use the great brakes we have to slow down and they take off too much speed. Then, as you might guess, they floor it coming out of the maneuver (and before they get it straightened out) and there is your spin.

A tip to help with that and what lines to take, look forward to the end of the turn and to the next point of interest while entering a turn. Hands follow the eyes and the car follows the hands.

[Christian1LE]

On a road course I start at 24 to 26 and aim for 32 hot.

[N Camarolina]

Originally Posted by Christian1LE

On a road course I start at 24 to 26 and aim for 32 hot.

Do you find that the tire (SC3) rolls over the sidewall at those low starting temps?

I was having that happen to me. Spoke with the guy that ran the business renting Camaros (at VIR). For avoiding excess tire wear on the shoulder, he found it's better to start the day at 30 and target 35, letting air out after each session, than to start the day at 24 or 26 and have it take most of the day to eventually get up to 35.

[VR Baron]

You’re talking autocross not road course correct?. On a 1le guys seem to use 32/34 front and 30/32 rear warm. Play with it in those ranges and see what you think. If with your softer std SS that has softer roll bars and softer mrc shocks you may find you like a bit more psi. Chalk the sidewalls at the flying shoe marking and don’t go lower than the top of it. If you find it understeers raise rear or lower front. Takes some trial and error to get it where you like it

[midnight1ss]

Yes I’m talking autox. I started at 30 hot but noticed that it went a bit higher when I left the car parked in the heat (thanks Florida).. so I lowered the pressure more in the front and rear by about psi since the current hot temperature was back at around 34 front and 31 rear. This completely made me understeer and when I got home I noticed I was using a tiny bit of sidewall in the front tires which of course explains the time lost and the understeer. I’ll leave it a bit more aired up next time around and I’ll use the chalk to measure since I’ve seen a few guys use that and you also mentioned it

[VR Baron]

Originally Posted by midnight1ss

Yes I’m talking autox. I started at 30 hot but noticed that it went a bit higher when I left the car parked in the heat (thanks Florida).. so I lowered the pressure more in the front and rear by about psi since the current hot temperature was back at around 34 front and 31 rear. This completely made me understeer and when I got home I noticed I was using a tiny bit of sidewall in the front tires which of course explains the time lost and the understeer. I’ll leave it a bit more aired up next time around and I’ll use the chalk to measure since I’ve seen a few guys use that and you also mentioned it

Cool. Try raising rear 2 psi and see how that does. What I have seen is you gain about 1psi per 45-60 second lap. In autocross you start out with cold psi and aim for your hot target. You can start out at your hot target and bleed back down after each lap, or start 2-3 psi low and just let tires go to the desired psi. It’s all up to you and what your tires are doing, course, temps that day etc.

[Christian1LE]

Originally Posted by N Camarolina

Do you find that the tire (SC3) rolls over the sidewall at those low starting temps?

I was having that happen to me. Spoke with the guy that ran the business renting Camaros (at VIR). For avoiding excess tire wear on the shoulder, he found it's better to start the day at 30 and target 35, letting air out after each session, than to start the day at 24 or 26 and have it take most of the day to eventually get up to 35.

Maybe, it takes me about 3 laps to get up to 30psi.(usually the fastest lap) My tire wear is good I think. I got 1100 track miles out of my last set and they had not corded yet. Had to replace them because of my yearly inspection. Probably had another 80 to 100 miles. That was with -2.5 camber and 0 toe.

The guy at VIR is renting cars to customers so lap times are not a priority. It's certainly likely higher pressures will make them last longer.

[N Camarolina]

Originally Posted by Christian1LE

Maybe, it takes me about 3 laps to get up to 30psi.(usually the fastest lap) My tire wear is good I think. I got 1100 track miles out of my last set and they had not corded yet. Had to replace them because of my yearly inspection. Probably had another 80 to 100 miles. That was with -2.5 camber and 0 toe.

The guy at VIR is renting cars to customers so lap times are not a priority. It's certainly likely higher pressures will make them last longer.

Well there's no doubt you are doing fast laps at VIR (you are crushing my speeds through the uphill esses!). The stated target temps in GM's HP supplement guide are something like 36-37 front and 36-38 rear. Maybe that's supposed to balance traction with tire longevity. I'm generally targeting 35-36 and am matching your speed and G loads in several turns with 2.0 front camber, but there are a few corners where you are faster and pulling higher than 1.3G, which is normally my max. Tire wear has been great though (1100 track miles so far and still a lot of tread left)

Have you tried 35-36 psi targets?

[Christian1LE]

Originally Posted by N Camarolina

Well there's no doubt you are doing fast laps at VIR (you are crushing my speeds through the uphill esses!). The stated target temps in GM's HP supplement guide are something like 36-37 front and 36-38 rear. Maybe that's supposed to balance traction with tire longevity. I'm generally targeting 35-36 and am matching your speed and G loads in several turns with 2.0 front camber, but there are a few corners where you are faster and pulling higher than 1.3G, which is normally my max. Tire wear has been great though (1100 track miles so far and still a lot of tread left)

Have you tried 35-36 psi targets?

I have, i started with 36 psi hot when i first got the car. I think the lower pressures give a bit better grip. Tire companies always advertise higher pressures because it's a safer pressure range for tires. Ie Hoosier will tell you to run like 42psi on their tires(for our cars) but competitive people believe run them at 30 to 32 psi.i don't think 35psi loses that much time(maybe 3 tenths?), I haven't tried to verify it in any way scientifically though. Track conditions change so much that i think it would take a real racing team to gather correct data on that. I know some racing series will force a minimum psi because lower pressure usually increases grip but you're stressing the tire more which could cause a catastrophic failure, especially on banked ovals.

I'm not any tire wizard though, I need more miles and more testing to have a better idea of what to do. All trial and error and talking to fast experienced drivers or engineers who you trust.