1st track day Saturday.... tire pressure question
09-05-2014, 09:22 AM
#16
Drifting
Thanks for the tips. Follow up question: How long does it usually take for the tires to reach optimal temps? i.e. how many miles, given a typical road track layout?
Before that happens I'm assuming I should be driving a bit off of top cornering speeds because they haven't warmed yet?
Before that happens I'm assuming I should be driving a bit off of top cornering speeds because they haven't warmed yet?
09-05-2014, 09:30 AM
#17
Nordschleife Master
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Thanks for the tips. Follow up question: How long does it usually take for the tires to reach optimal temps? i.e. how many miles, given a typical road track layout?
Before that happens I'm assuming I should be driving a bit off of top cornering speeds because they haven't warmed yet?
Before that happens I'm assuming I should be driving a bit off of top cornering speeds because they haven't warmed yet?
Spend your current energy learning the track and insuring that you have fresh brake fluid and decent pads.
Start your first session at whatever cold pressures you currently have and bleed down to whatever you feel is correct given the comments above.
Continue to bleed down after each session.
You won't be able to determine "perfect" hot pressures during your first weekend anyway, but the above will keep you in the ballpark.
Go have fun.
09-05-2014, 09:34 AM
#18
Drifting
Don't worry about it. You have plenty to do anyway and will not be pushing the car that hard.
Spend your current energy learning the track and insuring that you have fresh brake fluid and decent pads.
Start your first session at whatever cold pressures you currently have and bleed down to whatever you feel is correct given the comments above.
Continue to bleed down after each session.
You won't be able to determine "perfect" hot pressures during your first weekend anyway, but the above will keep you in the ballpark.
Go have fun.
Spend your current energy learning the track and insuring that you have fresh brake fluid and decent pads.
Start your first session at whatever cold pressures you currently have and bleed down to whatever you feel is correct given the comments above.
Continue to bleed down after each session.
You won't be able to determine "perfect" hot pressures during your first weekend anyway, but the above will keep you in the ballpark.
Go have fun.
Great thanks!
09-05-2014, 11:35 AM
#19
Rennlist Member
Thread Starter
http://www.motorsportreg.com/index.c...E#.VAnJv_ldV8F
I'll be in good company and we'll figure out how these cars are supposed to go around this track together.
Porsche Day at AMP.
I'll be in good company and we'll figure out how these cars are supposed to go around this track together.
Porsche Day at AMP.
09-05-2014, 07:33 PM
#20
My first ever DE, I was so overwhelmed that I forgot to check my tires until late in the day. I'd started at 34F/37R. When I finally checked them in the afternoon (a warm, sunny day in Southern California) my rear tires were around 52 psi! Lesson learned. Notice - that was an increase of about 15 psi over the course of the day. Moral: tire pressures can really increase during a DE!
The conventional wisdom, with which I agree, is that most street tires start getting slippery as they go over 40 psi. I try to keep my hot pressures around 35F/38R or thereabouts. It's worth mentioning that all 911's understeer, even the 991's. keeping the pressure differential F/R down to just 2 or 3 psi helps a little.
I follow the advice given above, start out at my normal 34/37. The first track session is never going to be run at top speed. The tires will warm up, but not excessively. With each successive run session, as the day gets warmer, the track gets warmer, and you get faster, you'll see pressures continuing to increase. So, as said previously, you'll end up letting out air after just about every session. In my experience, it's the 4th or 5th session of the day before the pressures have really stabilized and I can stop bleeding them.
Which means, after I've let out 10 psi or more over the course of the day -- when the tires cool off there isn't much air left in them. I usually bring a portable compressor to air up for the drive home. But if I forget to bring it I'll drive very carefully to the closest gas station to reinflate them.
Although tire pressures aren't the biggest deal at your first DE, it's always a good idea to get into good habits as quickly as possible. I always talk about tire pressures with every student that I instruct on the track.
DMoore
'13 991S
'13 970 GTS
The conventional wisdom, with which I agree, is that most street tires start getting slippery as they go over 40 psi. I try to keep my hot pressures around 35F/38R or thereabouts. It's worth mentioning that all 911's understeer, even the 991's. keeping the pressure differential F/R down to just 2 or 3 psi helps a little.
I follow the advice given above, start out at my normal 34/37. The first track session is never going to be run at top speed. The tires will warm up, but not excessively. With each successive run session, as the day gets warmer, the track gets warmer, and you get faster, you'll see pressures continuing to increase. So, as said previously, you'll end up letting out air after just about every session. In my experience, it's the 4th or 5th session of the day before the pressures have really stabilized and I can stop bleeding them.
Which means, after I've let out 10 psi or more over the course of the day -- when the tires cool off there isn't much air left in them. I usually bring a portable compressor to air up for the drive home. But if I forget to bring it I'll drive very carefully to the closest gas station to reinflate them.
Although tire pressures aren't the biggest deal at your first DE, it's always a good idea to get into good habits as quickly as possible. I always talk about tire pressures with every student that I instruct on the track.
DMoore
'13 991S
'13 970 GTS
09-07-2014, 10:41 AM
#21
Rennlist Member
Thread Starter
Had a great time. Wore off a little rubber and learned a little bit about car control.
From my original question I just left my tire pressure where I normally keep it on comfort settings (as suggested) and the tires performed quite well. Absolutely no evidence of rolling the side wall which surprised me some. Michelin Pilot Super Sports are fantastic.
V V V V V All cleaned up.
Last edited by CSK 911 C4S; 09-08-2014 at 10:30 AM.
09-07-2014, 01:38 PM
#22
You'll see the tread shoulder getting scrubbed some but never anything on the sidewalls unless you're severely underinflated. That kind of thing happened with some of the early high-aspect radials from the 70's but should be unheard of today. Yes today's tires are fantastic! Not all that many years ago only race cars with slicks were pulling 1 g. Now you got more than that on a car with street tires. Incredible!
09-07-2014, 02:39 PM
#23
Rennlist Member
A simple and effective way to find the appropriate tire pressure is with white shoe cleaner.
Put it on as instructed in the video below before you first session. Check its wear when you return to the pits after your session and adjust your tire pressure accordingly.
You need to repeat the entire process with each run. Track temp/ambient temp changes throughout the day. You familiarity with the track will also result in more aggressive driving which translates to more heat in the tires. More heat = higher tire pressure.
Put it on as instructed in the video below before you first session. Check its wear when you return to the pits after your session and adjust your tire pressure accordingly.
You need to repeat the entire process with each run. Track temp/ambient temp changes throughout the day. You familiarity with the track will also result in more aggressive driving which translates to more heat in the tires. More heat = higher tire pressure.
