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      09-02-2020, 12:45 AM   #1
asciimike
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Track Tire Pressures

Hey folks,

While prepping for a track day next weekend, the local chapter says the following about tire pressures, "For the performance driving you will be doing, you should inflate your tire to pressures above those normally used on the highway. With higher pressures, the tires will be able to generate higher cornering forces and will not roll onto their sidewalls during cornering. Recommended cold tire pressures are 38-40 psi in the front and 36-38 psi in the rear."

This seems pretty high: I'm running like 33 psi hot on Firehawk Indy 500's all around when autocrossing and seem to get plenty of grip, and a little higher on the street, where I can definitely feel less grip (then again, the tires aren't nearly as warm).

Thoughts? I know a lot of it comes down to personal preference, but just wondering what others are running and what people think make sense.
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      09-02-2020, 04:42 AM   #2
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I think that's a bit high as well, but it depends on tire. I aim for 33-35 hot in general, and they will warm up a lot more during a track day than AutoX. Keep an eye on them, and if you feel them start getting greasy drop a few PSI.
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      09-06-2020, 06:38 PM   #3
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I just did a day at Thunderhill 3-mile on Toyo R888Rs and started the day at 30 psi and after my first session all the tires were at 42-44psi. Dropped that down to 37-38 and went out again an hour later and they were up at 38-40.

If this is HDPE, your tires will likely pick up several psi while on track. By the end of the day my TPMS was yelling at me because I would go out on track with 28 psi but would come back at 38psi which is well within spec.

As a basic rule I've always taken tire pressure readings immediately once I'm back in the paddock and drop the psi down to whatever the recommended level is for that tire. Over the course of the day this should require little or no adjustment beyond the second session.
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      09-06-2020, 09:28 PM   #4
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Quote:
Originally Posted by dmf View Post
I just did a day at Thunderhill 3-mile on Toyo R888Rs and started the day at 30 psi and after my first session all the tires were at 42-44psi. Dropped that down to 37-38 and went out again an hour later and they were up at 38-40.

If this is HDPE, your tires will likely pick up several psi while on track. By the end of the day my TPMS was yelling at me because I would go out on track with 28 psi but would come back at 38psi which is well within spec.

As a basic rule I've always taken tire pressure readings immediately once I'm back in the paddock and drop the psi down to whatever the recommended level is for that tire. Over the course of the day this should require little or no adjustment beyond the second session.
Yes. I've found that upper 20's cold will heat up to 35-40 during a session. If you ran 35-40 cold, those would go to 50psi no problem. I think that is too much. But I'll stand to be corrected. I constantly check tire pressures during the day and am always changing to keep traction to a max. Track temps change. Outside day temps go up. It's rarely a set it and forget it if you want max performance.
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      09-07-2020, 06:35 PM   #5
asciimike
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I was running 33-34 hot on the track, which I think was a bit low (at least on the fronts, as the sidewall is pretty worn down). Definitely had them heat up to 40 or so which was wayyyyy too high and I was losing traction. Fairly certain their instructions are just off (unless people's normal tires really like it this high), and I let them know.

The other thing I ran into was the TMPS "low" warning putting the car into comfort mode with the temps that low. I had to go into "reset" mode (after stopping in the hot pits...) to get the car back into sport+. Seems like there are a few threads on disabling TMPS entirely (which is likely the "right" long term solution), but I'm curious if anyone has thoughts on how to keep it around but allow the warning pressures lower (e.g. allow like 28 to be considered fine when cold).
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      09-07-2020, 06:42 PM   #6
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How much your pressure you gain on hot tires are going to be affected by 3 things

1) tire compound
2) driving style/aggressiveness
3) ambient temperature

With that being said, what your starting psi should be set to depends on all these factors, and will change from person to person, in addition to day to day.

I generally start at 28 or 29psi and go from there. Aiming for around 35 or 36 hot temp after sessions.
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      09-16-2020, 12:00 PM   #7
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Quote:
Originally Posted by asciimike View Post
Seems like there are a few threads on disabling TMPS entirely (which is likely the "right" long term solution), but I'm curious if anyone has thoughts on how to keep it around but allow the warning pressures lower (e.g. allow like 28 to be considered fine when cold).
I set my cold tire pressure to 28psi, and then reset the TPMS (plan ahead because you'll need to drive a bit for the reset to work). On your first two hot laps, go easy to let the tires come up to temp gradually. This should keep you from rolling the tires on turns (and wearing the shoulders excessively). After a couple of laps, my tires are in the 34-36psi range and work pretty well.
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