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M2 Technical Topics > Track / Autocross / Dragstrip > MPS4S Tire PSI and Temp?

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      03-11-2024, 09:55 PM   #1
boba7523
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MPS4S Tire PSI and Temp?

Hi all,

Will be attending my first track event soon and would like to know what is the ideal PSI and temp to run these at for hot lapping? I recall seeing that anywhere from 35psi to perhaps 37psi hot is good for these tires and won't risk rolling over as they have a harder sidewall? I have a pyrometer that I'll be measuring during warm up to dial temp in as well.

OR, instead of a hard rule, should I be using tire temp to adjust PSI accordingly instead?

My camber is follows: -2.4F, -1.8R.

Appreciate the pointers!
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      03-11-2024, 11:32 PM   #2
ZM2
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I wouldn’t worry about a pyrometer or tire temps, and just focus on driving and keeping 4S psi’s 35-37psi hot.
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      03-12-2024, 11:43 AM   #3
ThreeStripes
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Agree. First event, car setup is not the focus, the driver is. Drink double the water you think you should. Focus on giving good points, your line, and the instruction you’re getting. If/when you get hung up behind a train don’t be afraid to pull into the hot pits and wait for space. The marshals can help.

Keep the TPMS screen up and you’ll see grip fall of as the tires crest 38psi and temps climb north of 140* but as ZM2 mentioned I’d leave the pyrometer at home for now.
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      03-13-2024, 01:32 AM   #4
boba7523
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Quote:
Originally Posted by ZM2 View Post
I wouldn’t worry about a pyrometer or tire temps, and just focus on driving and keeping 4S psi’s 35-37psi hot.
Quote:
Originally Posted by ThreeStripes View Post
Agree. First event, car setup is not the focus, the driver is. Drink double the water you think you should. Focus on giving good points, your line, and the instruction you’re getting. If/when you get hung up behind a train don’t be afraid to pull into the hot pits and wait for space. The marshals can help.

Keep the TPMS screen up and you’ll see grip fall of as the tires crest 38psi and temps climb north of 140* but as ZM2 mentioned I’d leave the pyrometer at home for now.

Thank you. What tire temp should I be aiming for during hot lap, and if it exceeds that, should I just exit to the pit lane to cool off and also release some psi?

Edit: I just did some more searching and it sounds like I can get about 3-4 hot laps on ~2mile track before tires get greasy. Can I do a cooldown lap any time I want during hot laps without getting any authorization? I'll be in beginner group...
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      03-13-2024, 10:10 AM   #5
ThreeStripes
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Quote:
Originally Posted by boba7523 View Post
Thank you. What tire temp should I be aiming for during hot lap, and if it exceeds that, should I just exit to the pit lane to cool off and also release some psi?

Edit: I just did some more searching and it sounds like I can get about 3-4 hot laps on ~2mile track before tires get greasy. Can I do a cooldown lap any time I want during hot laps without getting any authorization? I'll be in beginner group...
Talk with your instructor about how to manage tires during a 25min session but my advice is not to overthink it. My advice would be to set pressures to 32psi for your first morning session. Stay in tune with the grip the tires are communicating but don’t do “cool down” laps on hot track as a beginner. After the first session immediately after coming in and parking check pressures (which will be about 40psi give or take) and bleed down to 36. Rinse and repeat for session two. All you care about are hot pressures. Don’t sweat tire temps, just focus on listening to what the tires are telling you as they get greasy.

If/when your cold pressures dip below 28psi after sitting for 2hr the car may throw a warning and lock you into comfort. Don’t trip. Just reset the TPMS via iDrive just before going back out. While it’s resetting, it will allow you back into Sport/Sport+ and your tires will likely be back up above 28psi before it’s done resetting at which point you’re golden.

Your objective here is to get comfortable on track, managing traffic, and getting seat time. Car setup like alignment, tire temps and wear come later.

Last edited by ThreeStripes; 03-13-2024 at 11:08 AM..
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      03-13-2024, 05:14 PM   #6
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I run on street tires, and I'd suggest start at 32, then keep track of the dash pressures (you'll likely be talking w/ your instructor and they will cool down some after the session). Figure out how much they gained, and take almost that out, so that when hot you would be at 34 (i.e. if at 40 for end of session, pull 6# out). Same thing for after second session, but usualy only pulling 1-3#, and they will stay stable at that point unless you have a real long lunch break. Don't go out too low expecting them to fill out (I bring them back up to about 30 as my lowest). And remember that at the end of the day you want to fill them back up to about 40 for the drive home, or you will end up running too low and then needing to dig your pump out of the trunk at the roadside.

No way around it, you will eat your outside edges in front, but you can swap L-R each day to even it out a little. I go thru 2x the front tires to rears (now starting to trial the Conti extremes, and finding them to wear better despite being 200's).
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      03-13-2024, 09:56 PM   #7
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After your first day, reflect on the experience in a positive and try to begin committing to memory what you’ve gained from each session. It will be a humbling experience, trust it was that way for all of us starting.

Stay level headed as bad habits will try to form, key is learning not to cave to them but learn what to do to avoid the temptations.

Lastly, hope you enjoy it and it doesn’t turn out to be a one and done.
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