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Old 09-16-2012, 08:41 PM   #1
rocketman 12
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First Autocross next Sunday

I was wondering if anybody here would have some advice on where I should set my tire pressure, or if it should be changed from normal at all? I still have the original Pirelli's and have stock suspension.....for now.
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Old 09-16-2012, 11:55 PM   #2
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I've been playing with pressures right around stock 33-36psi the car with the ZL1 sways likes it around 33psi but the 23rd of this month is the next autocross since I aligned the car so we will see if that changes anything front camber is at -1.3 and I set the rear at -1.1 im hoping to kill this dang understeer
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Old 09-17-2012, 12:06 AM   #3
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The car seems to get very loose as the tires gain pressure from each run I readjust and set my pressures after each run
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Old 09-17-2012, 02:47 PM   #4
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Cool, thanks for the info!
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Old 09-17-2012, 05:47 PM   #5
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Originally Posted by ICTsccaCamaro View Post
The car seems to get very loose as the tires gain pressure from each run I readjust and set my pressures after each run
No reason you have to keep all four tires at the same pressure.

A little more than sticker up front helps turn-in, and a few psi less in the rear than up front can sometimes put a little more slip angle out back (less understeer). Less rear pressure tends to improve mechanical grip back there, which makes the car a little more resistant to throttle-on oversteer on corner exit.

I don't think I've ever set all four tires to the same pressure on any car that called for all four to be inflated the same even for purely street driving.


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Last edited by Norm Peterson; 09-18-2012 at 06:33 AM. Reason: bad splng
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Old 09-17-2012, 09:03 PM   #6
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i just ran my first one at the ls fest a few weeks ago. i also run the fronts higher than the rears by a couple of pounds. the pzeros will probably be fine at 36 front 32-34 rear. my invos like a few more pounds.
i normally do the hpdes and you run lower pressures there because your on track long enough to build up a lot of pressure,
my suggestion is run it with it in comp mode(two quick presses of TC button) and just learn the course the first few runs, i was turning in good times and not over driving like a lot of the high dollar cars.

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Old 09-18-2012, 06:02 PM   #7
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Can people post up some of there HOT tire pressures they are running front and rear just for a reference point?
Mabe add if your running large sways or a agressive alignment (ie. more than -1* camber) this may help also.
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Old 09-18-2012, 06:22 PM   #8
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What most everyone here is saying is technically correct, different tire pressure, alignment, and suspension settings will help shave time at the track.

But, given that this is your first time ever (i.e. you're not a serious autocrosser, at least not yet), you'd probably be better off just showing up stock and getting a general feel for limit driving and a basic sense of how the car behaves. Changing settings on the car will shave a little time once you have more experience and are up to driving consistently at the very limit, but at this point, it probably won't be worth it, particularly if you are just a casual autocrosser who drives on the road 99+% of the time and only once in a while autocrosses.
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Old 09-18-2012, 08:08 PM   #9
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good question about hot pressures. im no expert but i track with a lot of guys who have tons of real world race experience. hot pressure is what matters. all tires are different im learning. the invos like about 39 or 40 hot in the front and about 36 to 38 rear hot.
thats after two 25 minute sessions at a 4 mile track like vir. everything is smoking hot. when they cool off over night those same tires will read 32 front 30 rear. this is a little low for the invos so i need to pump them up a few pounds. i found this out the hard way a few months ago at VIR. i started the tires the second morning without adding any air. it was cool over night and my tires didnt feal right until the secong session.
for autocross you pump them up because you dont have time to build any heat in the tires in 46 seconds.
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Old 09-19-2012, 06:55 AM   #10
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Maybe not 6 - 8 psi from a single autocross run, but I've seen 2 psi on each of the first two . . .


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Old 09-19-2012, 01:15 PM   #11
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yeah as the day warms up and you get back to your parking spot and get out a pressure gauge it will show some change. it doesnt change during the run enough to make any difference at all. your right that it will climb over the day so a good tip from that point would be to check them before each run once you learn what you like.
the main thing is check them often to see what you have and then you are learning what your car/tires like. another reason they say to run them higher by a few pounds on the autocross is because lower pressure with those tight turns could damage the sidewall or roll a tire off the rim even at extremes.
for a first time the main thing is like the other guy said, dont get trick with it, just take you time and learn. shoot the bull with other guys and just get some seat time. its way easier than i thought it was going to be. i still like the tracks much better, but its cheap and fun.
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Old 09-19-2012, 02:10 PM   #12
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Adding some pressure for your autox runs helps prevent you from damaging the sidewalls and/or your rims. Definitely a good move.

Getting more involved in selecting the right tire pressures will require you to also get a tire pyrometer (and not the IR ones). When you come in from a run at the track, immediately get the inner, middle and outer tire temps. The temp profile across the tire can help you make the proper adjustments to tire pressure. Generally speaking, if the center temp is below the avg of the inner and outer temps, add air. If it's greater than the avg, let air out. The absolute values in the profile can help you identify any needed changes to the suspension, etc. There's a lot of info out in the interworld that can help you get the proper tire pressure setup for tracking your car. And adjusting tire pressures is one of the few things you can do to the car during a day at the track to help you go faster.
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Old 09-20-2012, 10:24 AM   #13
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Thanks for ALL the help, guys! I think for the 2-3 races I can get to yet this season, I'll just go with the recommended psi all the way around and check it after each run. I think I might also keep a notebook with pressures and air temps for future reference. If I go full-time next year(VERY likely), then I'll start playing around with different psi front to rear.

Doubleblank, were you at the Fest this year? That car looks familiar....
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Old 09-20-2012, 08:46 PM   #14
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I have done one autocross so far and was surprised at how hard you have to drive the car to post a competitive time. You will find the limit of your car and your driving skills quickly. My best time came with a mix of agressive/controlled driving. Don't over drive it into the corner or you will have severe oversteer. Quickly getting the car settled as you enter the corner then controlled acceleration at mid corner followed by hard acceleration between corners dropped my times. I still have a lot to learn but thats what I got out of one event. Oh and it was a total blast for me and my 14 year old co-pilot.
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Old 09-22-2012, 09:29 AM   #15
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I have done one autocross so far and was surprised at how hard you have to drive the car to post a competitive time.
That's because there is nothing in normal driving that compares in terms of the intensity and duration of a 45 second autocross run. You may briefly approach autocross intensity dodging the remains of a truck tire on the highway or during similar evasive maneuvers, but they're over and done with in a couple of seconds (think "start, three cone slalom, finish line, done"). In any other street driving, you're leaving more margin against losing control because the consequences are far more severe.


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Old 09-22-2012, 10:49 AM   #16
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That's because there is nothing in normal driving that compares in terms of the intensity and duration of a 45 second autocross run. You may briefly approach autocross intensity dodging the remains of a truck tire on the highway or during similar evasive maneuvers, but they're over and done with in a couple of seconds (think "start, three cone slalom, finish line, done"). In any other street driving, you're leaving more margin against losing control because the consequences are far more severe.


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Agree, on the street you can do spirited or agressive driving, but only a fool would test the limits of the car on public roads, especially here in the mountains where I live. On the autocross track, spirited or agressive driving isn't competitive. When some pretty weak cars are out running you by a few seconds, your shamed into finding your limits. Once your able to identify the car and driver limits you begin to work on technique at the limit. Its very challenging and fun. I encourage anyone that hasn't autocrossed to give it a try.
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Old 09-22-2012, 11:51 PM   #17
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Hey guys, what autocross class is the new 1LE SS going to be in? I am thinking of taking my 1LE once it arrives to an autcross at least, if I can't catch a track day just to experience how it handles at the limits etc.

Would appreciate the feedback?
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