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Old 07-22-2021, 11:04 PM   #1
Frmr2019WRX
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Default Tire Pressures for Track

I have Pilot Sport 4S tires with -2 deg camber all around and stock coilovers on my 2019 WRX. The tires are 245/40-18s. I want to know what tire pressures to run on track days (not autocross). It seems I get a lot of heat on the outside tread when running 32 psi. I don't want to change my cambers or suspension. Thoughts and recommendations appreciated!!
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Old 07-23-2021, 11:24 AM   #2
subydude
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Bump the pressure by 5-8 psi hot. You'll wear through the outer shoulder no matter what you do on track without more camber, but if you're unwilling to change it, just accept it and run higher tire pressure.
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Old 07-23-2021, 02:13 PM   #3
Frmr2019WRX
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Default Track Day Tire Pressure and Camber

Thanks subydude... I hope you don't mind clarifying... I should have stated the tire pressures were 32psi cold. So I should start with 37-40psi cold? Or, start with 32psi cold then check them when they're hot and add another 5-8psi. I think both should get me in the same neighborhood. For Camber... I have Whiteline offset (fixed) tophats. Could I mark my camber bolts where they are with -2 deg then adjust them to (say -2.5 to -3 deg) for track days then move them back for street (using magnetic camber tool). Would this throw off my toe? Or, should this be done by a professional?
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Old 07-23-2021, 02:19 PM   #4
subydude
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32 cold will end up around 37-38 hot on track since the usual pressure gain is roughly 5-6 psi. I'd bump the starting pressure up 3ish psi and that should be fine.

You can mark the camber bolts and move them. It will affect toe when you move camber, and an alignment shop or someone local to you can show you how to fix that on your own with simple tools. There's a lot of guys that adjust their camber at track events then adjust back when they get home. -3 up front will help a lot for tire shoulder wear/heat.
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Old 07-23-2021, 02:36 PM   #5
Frmr2019WRX
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Thanks!
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Old 07-23-2021, 06:13 PM   #6
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I've always chalked and checked, starting at 45 front, 40 rear. To do this, mark the about an inch of outside tread, then down the sidewall maybe an inch. You can use actual chalk or paint or whatever you have. After a run, look at how much of the marking has been worn off. If you've still got marking on the actual tread, drop 3-5 pounds and run again. When you have nearly no rollover, you're good.

Your ending pressure can be different based on outside temp, what the track is like and such.
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Old 07-23-2021, 07:50 PM   #7
Frmr2019WRX
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I'll try increasing pressure. I didn't get any wear on the sides - only on the tread. But, with more pressure I may move some heat/wear away from the edge and into the center.
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Old 08-04-2021, 07:29 PM   #8
Jack
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You'd ideally want a little over the edge of the tread, starting on the sidewall. I wouldn't add air if you don't see wear going down the sidewall at all. Expect to see maybe 1/16th inch on the sidewall if it's perfect.

Now, you can go away from perfect to get the car to handle the way you want it to. If you add air to a perfect rear, you'll get less rear contact patch and thus more rotation (oversteer). Cheaper than suspension parts.
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Old 08-05-2021, 09:43 AM   #9
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I would definitely recommend chalking the tires or use tire crayons (if you don't care that it won't wash off easily). Those little triangles on the sidewall of the tire are wear indicators if you don't have chalk or forget it. The tip of the triangle is usually pretty close to where you want the rollover to be in my experience.

You don't want to over-inflate or you'll sacrifice traction, but start higher cold and bump them down as you get a feel for how much pressure will increase with the heat and how much the tire is rolling over.

Jack is very much correct that pumping up the rears will make the car rotate. You can really get the car to handle the way you want with just tire pressures alone.

Hope that helps a bit.
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Old 08-14-2021, 06:55 PM   #10
whmcmillan
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Thank you for the information!
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Old 09-20-2021, 08:51 PM   #11
GRBrad
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Started auto crossing my car and was blown away but how just adjusting a few pounds front and rear got the car to handle so much differently. Upped the rear tires to about 38 cold and the car really started to rotate for me. Need to bring a pump next time and really mess around with the pressures
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