09-01-2020, 11:45 PM | #1 |
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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. |
09-02-2020, 03:42 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, 05:38 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, 08:28 PM | #4 | |
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09-07-2020, 05:35 PM | #5 |
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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, 05:42 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, 11:00 AM | #7 | |
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10-12-2021, 08:07 PM | #8 | |
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Took me a while to figure that out. Falken 660's M2 base - track built - Porsche Killa |
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10-14-2021, 05:58 PM | #9 | |
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these pressures are normal for stock standard street tires. the assumption is that you have stock street tires. they need to be higher as their sidewalls are not as stiff as semi slicks and will roll and flex off the rim if the pressures are too low ideal pressures you should be running HOT Street tires is 40 PSI (300 TW) High Performance but not semi slicks 36-37 (200 TW) these tires include Michelin Cup2, RE71Rs etc etc Actual PROPER semi slicks AO50s, Z221, DZ03g, RE11s, 888R etc 32-34 (100 TW or less) Falken 660, Firehawk Indy 500 etc are NOT actual semi slicks and running them at such a low PSI on a high speed track is not recommended. there is a reason why its recommended for 38-40. Last edited by Robbyjai; 10-14-2021 at 06:10 PM.. |
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10-14-2021, 06:12 PM | #10 | |
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you are introducing a hell of a lot of issues under inflating the tires incorrectly. Issues you will experience - side wall flexing - rolling on rims - reduced grip due to rolling on rims - bowing of your tires where the centre contact patch bows upwards and only the sides are in contact resulting in very reduced grip there are a number of factors you need to take into consideration You need to consider the weight of the car the lighter your car the lower PSI you can run. the heavier your car the higher PSI you NEED to run context. ive spent 13 years on the race tracks and ive seen street tires roll off the rims from under inflation and all sorts of issues. The local chaper who gave this advice "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." is 100% bang on working on the assumption that people are driving 300TW tires Last edited by Robbyjai; 10-14-2021 at 06:36 PM.. |
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10-14-2021, 06:38 PM | #11 | |
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google it sorry if it sounds harsh but incorrect information could lead to someone misunderstanding applying your generic one size fits all rules and then ends up spearing into a wall or another car or having a tire blow out and flipping the car |
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10-14-2021, 06:47 PM | #12 |
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10-15-2021, 03:32 PM | #13 | |
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I've found starting around 35 psi cold leads to a good first session of the day (ending at 38-40) and adjust down from there if end-of session psi is greater than 40-42. Above 42 psi is noticeable loss of grip. If you drop them a lot during the day, be sure to add back before the drive home. PS with much heavier cars than the M2C, I've run low 40s no problem. PPS I definitely disagree with super low starting pressures. Way too much heat buildup occurs, which does get the tires to proper psi but at a cost of grip and tire wear.
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10-16-2021, 08:03 PM | #15 |
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Been targeting 36-38 hot on the front for my M2C with stock PSS. Seems to be pretty happy around this range. Anything lower and the car felt sloppy.
Might be able to go a little lower in the rear, since those are little wider. |
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12-29-2021, 10:31 AM | #16 |
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I target 35psi hot on track days so usually start around 30 and go from there. I do have front tire outside excessive wear but I just assume that's because of no camber plates.
That is really interesting to run up around 40. |
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02-06-2022, 01:19 PM | #17 | |
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I’m far from an expert track driver, which I would argue makes this approach even more dangerous. My experience with this tire is that it grips up and is happy between 33-37psi and above that it falls off quickly and can get squirrelly. I don’t have any fancy white papers to back me up, but it’s worth mentioning that some times real life and what you read on the internet don’t always line up. In this case, 40psi on a 300tw PSS on a M2 is absolutely not the PSI the tire performs at best in my experience and is actually quite sketchy. Last edited by Wolfman’s Brother; 02-06-2022 at 01:28 PM.. |
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02-07-2022, 02:03 PM | #18 | |
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Targeting 40psi hot with a 300tw Michelin PSS is a sure fire way to have a shitty time and is in no way the ideal pressure to run in my experience, or the experience of many others on this forum. The fact that I followed this logic in the name of safety to the opposite intended effect is absolutely hilarious since there was no impact to life/property. How I’m the only one speaking up on this, puzzles the heck out of me. |
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02-07-2022, 03:27 PM | #19 |
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I ran the PS4s for almost two years and over 30 track days and anything over 38 PSI hot will result in the tires greasing up. Start at 32-33 and monitor your tire pressures. Pull into the pits to let some air out midway through your first session when you are going to see the most pressure gain since you will start in cold tires and in colder weather.
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02-07-2022, 06:45 PM | #20 | |
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Sorry for beating the dead horse here but, given the irony of the situation I just can’t let it go. |
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02-07-2022, 09:13 PM | #21 | |
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Start at a reasonable cold pressure (start with door sticker?), get them up to temp, bleed down to pressure of choosing (33-38 seems decent for this car stock, based on previous responses?), turn some laps . That isn't always practical for most HPDE environments I've been too sadly, so there is a compromise somewhere. Random hypothesis: 35 is the recommended cold pressure and usually tires minimally heat up on the street (couple psi increase). That would have you land at ~38 hot, which seems to be inline with previous things I've read for "street tires" from Michelin, on a relatively under-tired car no less. Let me see if I can find the reference. Edit: Found the source regarding PS4S. Read further down the article. There is mention that Sport Cup 2s and PS4S take to pressures pretty similarly. "Hot pressures should roughly be similar to the recommended cold pressures for the street. Just make sure to change back to the road pressure settings before you leave the track. The PS4S and the Pilot Sport Cup 2 both have a similar theory on track pressures. It's preference and driving style, but in general mid-30s psi (hot) is recommended." https://www.google.com/amp/s/www.mot...-sport-4s/amp/ |
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02-10-2022, 08:19 AM | #22 |
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My 2 cents. This starts out OK but...
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. This is wrong.... Recommended cold tire pressures are 38-40 psi in the front and 36-38 psi in the rear. That is the ideal hot pressures I've found for the M2C on PSS. Also what Michelin tire experts agree. Anything over 40psi starts to loose grip. Although when tracking heavier 5 series cars, I aimed for 40-42 max and suffered greasy feeling at the end of the sessions. In order to achieve 38 psi max, I've started sessions as low as 32. I hate starting below that and may finish a session above the 38. I bleed off a bit and the next session is ideal.
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