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Can anyone recommend a tire pressure for my 2009 Cayman S. I'll be taking it on the track for a few laps later this week. Should I go with what the door says, or is another pressure preferred for track use?

FYI, the car has the stock 19" wheels (with stock size Michelin Pilot Sport 2 Tires).

Thanks for your help.
 

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What type of track event and what is your experience? If you're a novice at a DE suggest go with the door label- should be 31psi I think for 19s. As you gain experience, check pressure after a session and adjust as needed. For PS2s I found they would feel greasy at pressures of 38psi and above hot.
 

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The recommended door sticker pressure for the 19" of 32psi front and 34psi rear always gets my rear tires to 40psi on spirited drives so I am now running them at 31psi front and 32psi rear when cold. Gets them up to 37 or 38 psi.
 

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37 psi at full hot works for me on 19s. I run door jamb for first session, then check them after first run and I'm usually over 40. I bleed out down to 37 on all four and that seems to work ok. The best? Dunno. Better than 40, that's for sure.
 

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Start the tires at 27 psi cold on all four corners. Check pressure as soon as you come in and look for no more that 34 hot. If higher, then wait for the tires to cool and bleed the pressure down by 2/3 of the overage (i.e., if they were at 37 bring them down by 2 pounds once cool). Repeat. Door pressures are for mileage and street safety and have no relation to what is correct on track.

Don't bleed hot or you will not know what your proper starting pressure should be.

Cheers,
 

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Start the tires at 27 psi cold on all four corners. Check pressure as soon as you come in and look for no more that 34 hot. If higher, then wait for the tires to cool and bleed the pressure down by 2/3 of the overage (i.e., if they were at 37 bring them down by 2 pounds once cool). Repeat. Door pressures are for mileage and street safety and have no relation to what is correct on track.

Don't bleed hot or you will not know what your proper starting pressure should be.

Cheers,
Krok:

Sorry, I'm not seeing that as a viable way to do track days. When exactly does the tire ever cool down? I see what you're trying to do, but you're fighting hot vs cold pressure all the time. Cold means COLD. Most of the time, the engine and the brakes keep my tires hot for an hour or more after a run.

36 or 37 HOT right after a run for all 4 tires is a good target for me and for most people. When most summer tires get to 40 psi HOT, they start to feel greasy and don't work well. The best way is to start out with door pressure or a little less, do a few laps, come in to hot pits and check air...let some air out...down to 36 on all 4 corners, go out and finish the run. Check again after the run. Set them at 36 HOT again. Now leave them alone until the next run. Doesn't matter what the cold pressure is. A pocket sized tire gage is really a good thing to have.

As the track warms up during the day and as the driver warms up to the track and starts putting more heat into the tires, the pressures keep going up, so keep checking those hot pressures and setting them at 36.

At the end of the first day, I usually put 5 psi into each tire. This is enough air to get me to motel and to dinner etc driving like a normal person. Don't push the car with low pressures. Next morning, go out on that pressure and heat up the tires again. Aim for 36 HOT again. If it comes out 35 HOT after 1st run or first few laps, that's OK. If it's 32 or lower, you should add air.

I just don't use cold pressures until the event is over and I'm packed and ready for the drive home. Then and only then do I think about cold pressures. What's the point of using cold pressures at the track? They really don't matter.

This is not a race situation where you need perfect pressure for that track and have to fill tires cold to reach the right hot pressure. Every track is going to heat tires differently and each corner of the car gets different amount of work and heat for each track...so trying to set perfect cold pressures for track use is really an arduous task. People who are at all new at this stuff have a lot better things to think about than all that computation. You just need a starting point first thing in the morning. Door pressure is OK. A little less is OK. Then set all 4 tires while they're hot.

If you want to know what "proper starting pressure should be", you can check pressures at the end of the day after the car has sat A LONG time, but in my experience, it's not really accurate because temps change all the time and so does the illusive "proper starting pressure". Ignore cold pressures and work with hot pressures only during track events. It just works better and is simple and easy.

36 all 4 corners hot off the track works for Nitto NT01 and Hankook Ventus and MPSS on my car. Starting pressure of what you drove the car to the track on is OK for a couple laps until tires are sufficiently hot.

:cheers:
 

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I try to maintain the 'door pressures' once up to temperature. Make sure you re-inflate them before the drive home though.:)

Trev:

Door pressure is recommended COLD PRESSURE. That anticipates that the pressures will rise as you drive the car normally. It's for setting the tires before you start off in the morning... ON THE STREET.

Don't try to maintain door pressures on hot laps. It's not enough air. Also, the car will work better with all 4 tires at the same pressure HOT. Most tires are designed to work best at around 35-36 psi HOT.

HOT pressures are great because the tire doing the most work will heat up more and gain more pressure as you do your hot laps. It still will work best at 36psi. The corner that does the least work will rise the least amount...but it also will stick best around 36 psi.

If you keep really low hot pressures, the sidewalls will roll over and you'll get really bad tire life. The front tires especially will wear out on the outside edges.

:cheers:
 

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Trev:

Door pressure is recommended COLD PRESSURE. That anticipates that the pressures will rise as you drive the car normally. It's for setting the tires before you start off in the morning... ON THE STREET.

Don't try to maintain door pressures on hot laps. It's not enough air. Also, the car will work better with all 4 tires at the same pressure HOT. Most tires are designed to work best at around 35-36 psi HOT.

HOT pressures are great because the tire doing the most work will heat up more and gain more pressure as you do your hot laps. It still will work best at 36psi. The corner that does the least work will rise the least amount...but it also will stick best around 36 psi.

If you keep really low hot pressures, the sidewalls will roll over and you'll get really bad tire life. The front tires especially will wear out on the outside edges.

:cheers:


Thanks Sixisenuff. I don't take my CS on track more than about a couple of times a year due to owning a dedicated track car as well, but next time I do I shall take your advice.
 

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Krok:

Sorry, I'm not seeing that as a viable way to do track days. When exactly does the tire ever cool down? I see what you're trying to do, but you're fighting hot vs cold pressure all the time. Cold means COLD. Most of the time, the engine and the brakes keep my tires hot for an hour or more after a run.

36 or 37 HOT right after a run for all 4 tires is a good target for me and for most people. When most summer tires get to 40 psi HOT, they start to feel greasy and don't work well. The best way is to start out with door pressure or a little less, do a few laps, come in to hot pits and check air...let some air out...down to 36 on all 4 corners, go out and finish the run. Check again after the run. Set them at 36 HOT again. Now leave them alone until the next run. Doesn't matter what the cold pressure is. A pocket sized tire gage is really a good thing to have.

As the track warms up during the day and as the driver warms up to the track and starts putting more heat into the tires, the pressures keep going up, so keep checking those hot pressures and setting them at 36.

At the end of the first day, I usually put 5 psi into each tire. This is enough air to get me to motel and to dinner etc driving like a normal person. Don't push the car with low pressures. Next morning, go out on that pressure and heat up the tires again. Aim for 36 HOT again. If it comes out 35 HOT after 1st run or first few laps, that's OK. If it's 32 or lower, you should add air.

I just don't use cold pressures until the event is over and I'm packed and ready for the drive home. Then and only then do I think about cold pressures. What's the point of using cold pressures at the track? They really don't matter.

This is not a race situation where you need perfect pressure for that track and have to fill tires cold to reach the right hot pressure. Every track is going to heat tires differently and each corner of the car gets different amount of work and heat for each track...so trying to set perfect cold pressures for track use is really an arduous task. People who are at all new at this stuff have a lot better things to think about than all that computation. You just need a starting point first thing in the morning. Door pressure is OK. A little less is OK. Then set all 4 tires while they're hot.

If you want to know what "proper starting pressure should be", you can check pressures at the end of the day after the car has sat A LONG time, but in my experience, it's not really accurate because temps change all the time and so does the illusive "proper starting pressure". Ignore cold pressures and work with hot pressures only during track events. It just works better and is simple and easy.

36 all 4 corners hot off the track works for Nitto NT01 and Hankook Ventus and MPSS on my car. Starting pressure of what you drove the car to the track on is OK for a couple laps until tires are sufficiently hot.

:cheers:
He asked for advice and I am telling him to do what I know works - and believe is quite viable - and how I coach students. It works very, very well once they start to listen. YMMV.

I never said let the tire get back to the original cold pressure, I said let it cool (please re-read my post). The tire may have only cooled from 37 to 31, but now you bleed to 29 just before the next session (up from the starting 27). This sets the intra-session reference point for the rest of the day (tire pressure movement between sessions) and allows for more accurate pressure/temperature control. If you bleed hot you need to check/adjust again to know the starting pressure and gain in the next session. For DE temp control is not about ultimate traction it is about predictability and protecting the tire. Most street tires start to delaminate at the temperature equivalent of 36 hot when driven hard - more so with less than optimal camber.

After doing this a few times a driver can learn to nail the hot pressure right out of the box based on ambient and not have to adjust much if any all day (unless it gets much warmer or colder). I can tell you the pressure gain within a pound for my race tires based on ambient. And by starting all of the tires at the same temp you learn very quickly how the car is handling by comparing temp/pressure gain.

NT-01s will turn their fastest lap on the third lap out at 32 (29 staring pressure) and a Hoosier R6 (assume R7?) want to be at 30 and will do its fastest lap on the second or third lap our depending on the pace of the out lap - but both will overpressure on the fourth to fifth lap hence the reason for 27 starting for a full session. A Yoko slick likes 29-30 and is quickest on it second to third lap if medium compound and third to fourth lap if hard compound. We start them at 21 for qual and 19-20 for the race depending on track and ambient. We did quite a bit of testing to learn this.

Frankly, for most folks where we are trying to keep it simple I just tell them to set the pressures at 27 F/R and go have fun and not worry about it for the rest of the day. This is enough pressure to support the tire and provide good grip, but no so much that it will ever really overpressure - especially with a newer driver.

Cheers,
 

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As a base for tire pressure, I would start around 30 psi and CHALK the tires at the little triangles on the edge of the tire. Check the roll over of the tire after the first run. You should be rolling over to just above the limit triangles (little triangles at the edge of the tire near the sidewall that mark the max roll over of your tire. Didn't know you had them or what they were for, did you?).

If you are rolled over too much, add air. If you are rolled over too little then let air out. I would go 2psi at a time until you get consistent temps/roll over.
 

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As a base for tire pressure, I would start around 30 psi and CHALK the tires at the little triangles on the edge of the tire. Check the roll over of the tire after the first run. You should be rolling over to just above the limit triangles (little triangles at the edge of the tire near the sidewall that mark the max roll over of your tire. Didn't know you had them or what they were for, did you?).

If you are rolled over too much, add air. If you are rolled over too little then let air out. I would go 2psi at a time until you get consistent temps/roll over.
San:

Chalking the tires is a good trick for autocross or DE, HOWEVER:

1. Chalking the tires before they're warmed up isn't advisable. It's going to give false readings. If you fill tires to 30 psi cold, the tire will go pretty far on their sidewalls until they warm up. Better to do this after the tires are hot. That's when you want to have the tires just right, not while they're cold at 30 psi. Once the chalk is gone from the cold tires lap, it can't tell you anything that's true. You'll be putting too much air in the tires.

2. The structure of most DEs doesn't allow time for that sort of stuff during sessions. To do it right, you'd have to do a couple good hot laps and have tires up to temp, then pull into hot pits and then get out of the car and mark all 4 tires. If you can arrange it, fine. For beginners, there are far bigger fish to fry like learning the track, learning what an apex even is, what the difference between early and late is. yadayadayada. So, if I were the instructor, I'd have to have pretty high confidence in the student. Then I'd want him to talk over his plan with me prior to the run. To do this in a valid way, the tires must be at full temp before you mark them....Then go out and do your laps, then read the chalk marks.

3. That said, I'm not opposed to starting the first session with 30 psi in each corner. After a few hot laps, most tires will increase in pressure 4 to 10 psi depending on if it's the corner doing the most work or the one doing the least work. For front wheel drive cars, the fronts do almost all the work, so the delta of pressure increase can be even more.

You check the tires hot at the end of these laps, or at the end of the session. If you then set your hot pressures at 34 to 36 psi, (all the same pressure but which exact pressure depends on the tire used, the amount of negative camber, the accuracy of your tire gage etc.)

My car with MPSS or Hankooks, my camber settings and my tire gage works well at 36. Much higher and the tires start to slip around too much. Too low and they'll blister from too much heat. I've noticed, when they get up to about 39psi, they start to feel greasy and the car is difficult to drive quickly.

What I'm trying to say here is that all these sorts of methods have their place at some point in learning your car and your tires, but that for the infrequent adventurer or the new guy, a lot of complicated procedures is too distracting from the business at hand. Keep it simple, get in the ball-park. Get your laps feeling good. If I can get two perfect sessions, where the car and I are in synch and I get all the turns as intended, smooth, connected, fast and right at the limit out of a weekend, I feel pretty good.

So here it is again...simple:

1. Set all tires at 30 psi (this part isn't critical...read on to see why)

2. Do two or three pretty hard laps. They don't have to be prize winners but you have to push sufficiently hard to get the tires up to temp. That's not possible for Novice group guys...So you newbies, just set all 4 at maybe 32 psi and do nothing but learn the other stuff for two sessions....then start adjusting for hot pressures..

3. When you feel you've got the tires hot, pull off the track to a safe place (hot pits or wherever the officials tell you), turn off the car...DO NOT put on the hand brake. Put the car in gear with engine off. Get out of the car, pull out your handy pocket sized tire gage, check the left front. Drop psi to 35. Check left rear. Drop psi to 35.
Check right rear. Drop psi to 35. Check right front. Drop psi to 35. Get back in the car and go back out for the remainder of the session. The car should feel a lot more dialed in.

4. After the session, Check them again. Drop pressure as needed down to 35psi. Hopefully, you won't have to add because that's inconvenient!

5. Let the car and tires cool down. DO NOT RECHECK THE PRESSURES. Re-torque the lug-bolts if you're looking for something to do.

6. Go back out and run your next session. If the car starts to feel slippery again, go back to the safe place and drop the hot pressures to 35 again. This often happens because a. When the tires feel good, you go faster and that heats them up more. b. As the day goes on, usually the track and ambient temp goes up and that heats the tires. If you heat them enough so they're approaching 40 psi, they're probably going to feel slippery.

7. If it rains or becomes cold, you may need to add air. It's good to have a compressor so you don't have to stand in line for track air. You can guesstimate the change in air pressure, but then when you come in, check your guesses.

Here's an example of that scenario: I'm in B Group. After lunch, A Group went out in a light rain. It's still cloudy but not raining anymore. I know the track has cooled. The temp is 10 degrees lower than before.

Check the cold pressure of each tire. Add 3 psi to each one, wherever it is, before you go out. At the end of your session, check hot pressures again and adjust as needed.

8. Make a note, mental or physical, of the HOT pressures when the car works the best. That should be your target pressure for all 4 tires next time.

9. Don't think about cold pressures until the day/weekend is done and you're going home. If you're driving on the tires you ran, you'll want to let them get as cold as possible while you pack up, then put something near your normal cold street pressures in them. If they're still a bit hot, you can use a lower pressure ...~1 psi for each 10 degrees that the tire/wheel is hotter than ambient. You'll have to guess. When you get home, check set them when they're really cold before you drive on them again.

10. Monitor your tire wear. If the track is clockwise, the left side will be doing more work. Generally, the fronts are the ones that get the most wear. Consider rotating the front tires or both tires from side to side. It's good to buy non-directional tires for this reason.

This system isn't perfect, but it gets you close enough to do good solid laps, feel a connection to the track and the car and have a good time without spending your whole day on tires. There's a lot of other things to do and learn.

If you ever go to a free-lapping day where the track is open for the day, you can play with chalk and tire pyrometers and all other sorts of fun toys, but when you're learning how to drive the car, try and just learn how to drive the car and not distract yourself with the pursuit of the perfect tire pressure. Likewise, if you go racing and you manage to have a pit crew, you can put them to work an all sorts of good stuff. There are many books on this. Most guys have a system and it's good to have a system. I've tried a lot of them. In the end, at a track day when you're not racing, this will get you close without a lot of pain.

:cheers:
 

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You guys seem like real tire pressure freaks so let me ask you a question about adjusting pressure for handling. Every "cheat sheet" I've ever seen says to RAISE rear pressure to decrease oversteer but now I've heard from someone who should know that that is just the opposite. You should LOWER rear pressure. Is that right? And, if so, why does everyone (e.g. Tire Rack) have it wrong? Thanks.
 

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It depends entirely as to whether your pressures are too low or too high to start. For every tire, there is a pressure that will give you the maximum grip level. If you reduce pressure below that, it will decrease grip. If you increase above that, it will decrease grip. Generally speaking, the loss of grip when running too low (tire deformation) is worse than the loss of grip from running too high (smaller contact patch).

For a typical consumer who runs pressures well below maximum grip in order to balance grip during competition and tire life during daily driving, increasing pressure will increase grip. For a racer whose pressures are already optimal, any change at all to rear pressure will cause an increase in oversteer, not a decrease. The only time it helps is if pressures are set too high, which is not uncommon as higher pressures help increase responsiveness in transitions.
 
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