DE Event Tire Pressure....
03-09-2011, 10:14 PM
#16
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tire pressures on street tires at HPDE's
Bob I think Steamboats response is the most accurate the only way to tell the right pressure for that car, that tire, that day, and that set up is with tire temps. we are all talking hot temps. Bluntly I do not trust most, not all but most of the MFG recommendations on pressure for street vehicles on street tires because there considerations for tire pressure has to do with ride, and comfort. Not all the time but much of the time. Porsche might be excluded. but if this is a general discussion then I would caution about relying on the MFG recommendations.
I would have to see the tire temp between the 38- 40 range you mention and the 45 I suggested on a pure street tire, that would be interesting. I never ran street tires on my GT3 so i can not comment on my experience with streets only what I have been told.
I would have to see the tire temp between the 38- 40 range you mention and the 45 I suggested on a pure street tire, that would be interesting. I never ran street tires on my GT3 so i can not comment on my experience with streets only what I have been told.
Hope to see you at Mid Ohio in April. Regards, Ray
03-10-2011, 10:50 AM
#17
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Starting last year I began to gather tire data, including cold pressure, hot pressure and temperature across inside, center and outside of the tread. Ambient temp and temp of track is good data to collect from AM to PM. This year I plan adding hardness data with a durometer.
What I've learned thus far in my 1.5 ton 3.2 liter 911 Carrera after many 20 to 30 minute sessions:
Tires: NT01's 215 45 17 front and 255 40 17 rear
Ambient Temp: +/- 75 f.
Tire PSI Cold: 36 rear / 29 front
Tire PSI Hot: 41 rear / 33 front
Tire Temperatures: Ranges from 160 to 170 degrees F across face of tread.*
*Tire temperature falls off due to cool down lap at the end of a session plus pit-in and drive to
paddock slip. Even with that, I figure the rate of cool down is roughly consistent each time I come in.
What I think I know is the higher hot pressure adds stability to my set-up by making a relatively stiff side wall NT01 even stiffer. I feel higher pressure, as opposed to lower pressure, is adding tread contact patch strength and stability, particularly slip angle firmness under load. Tire temperature contributes as well.
What I've learned thus far in my 1.5 ton 3.2 liter 911 Carrera after many 20 to 30 minute sessions:
Tires: NT01's 215 45 17 front and 255 40 17 rear
Ambient Temp: +/- 75 f.
Tire PSI Cold: 36 rear / 29 front
Tire PSI Hot: 41 rear / 33 front
Tire Temperatures: Ranges from 160 to 170 degrees F across face of tread.*
*Tire temperature falls off due to cool down lap at the end of a session plus pit-in and drive to
paddock slip. Even with that, I figure the rate of cool down is roughly consistent each time I come in.
What I think I know is the higher hot pressure adds stability to my set-up by making a relatively stiff side wall NT01 even stiffer. I feel higher pressure, as opposed to lower pressure, is adding tread contact patch strength and stability, particularly slip angle firmness under load. Tire temperature contributes as well.
03-10-2011, 11:39 AM
#18
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imho when rear end goes above 38-39 psi car get much more unstable than it may be acceptable. and when close to 45 it is just not right at all.
again, exact split between front and rear pressure depends of quite many factors of overall car setup but usually 4 psi works best for me. 33f 41r is quite a much, I would definitely try 32f 36r hot first and then would increase it if tire wear will be visibly wrong or temperature will be very uneven. if one does not have a pyrometer and no friends to borrow one - just use your own hand with caution, if tire heats up extremely uneven you will be able to feel it, with a bit of practice hand picks up those temperature differences quite well.
and if we speak of street tires on cold spring morning - start at 30f 32r, do 2-4 laps to warm them up, then do a quick stop and check for how much your pressure got changed, bleed if needed and memorize how much did you bleed. also try not to start on tires having less than 28psi in them, it will damage tires too much during warmup laps. at AX maintaining proper rubber temperature is a whole freaking circus, at DE it is much simpler overall but still same applies - you can drive out to service roads before your group is called, drive and brake hard a bit of times to warm up rims as much as you can to raise pressure a bit so your wheels would not be dead cold like ambient 40-50 something degrees before you go on a track. but street tires are not r-comps and they will not change their pressure as dramatically, so, you probably will be fine anyway, there is no reason to freak out about that, just be aware that tires pressure is something you should not forget about.
again, exact split between front and rear pressure depends of quite many factors of overall car setup but usually 4 psi works best for me. 33f 41r is quite a much, I would definitely try 32f 36r hot first and then would increase it if tire wear will be visibly wrong or temperature will be very uneven. if one does not have a pyrometer and no friends to borrow one - just use your own hand with caution, if tire heats up extremely uneven you will be able to feel it, with a bit of practice hand picks up those temperature differences quite well.
and if we speak of street tires on cold spring morning - start at 30f 32r, do 2-4 laps to warm them up, then do a quick stop and check for how much your pressure got changed, bleed if needed and memorize how much did you bleed. also try not to start on tires having less than 28psi in them, it will damage tires too much during warmup laps. at AX maintaining proper rubber temperature is a whole freaking circus, at DE it is much simpler overall but still same applies - you can drive out to service roads before your group is called, drive and brake hard a bit of times to warm up rims as much as you can to raise pressure a bit so your wheels would not be dead cold like ambient 40-50 something degrees before you go on a track. but street tires are not r-comps and they will not change their pressure as dramatically, so, you probably will be fine anyway, there is no reason to freak out about that, just be aware that tires pressure is something you should not forget about.
03-10-2011, 01:45 PM
#22
Race Car
Thread Starter
Thanks to all who posted information. My DE event went well and the car was great as long as I kept the pressures in the 36 to 40 psi range.
I found this thread to be quite informative and hope others did as well.
Scott
I found this thread to be quite informative and hope others did as well.
Scott
03-10-2011, 01:45 PM
#23
Rennlist Member
it is a pretty typical sample of a response here - people who do this stuff for 10+ years have their own interests in pretty different areas and get easily annoyed when stuff they have no interest in gets repeatedly surfaced up by people who only start on their hobbies. as I lurk around those forums for last 3 years there is hardly any principally new topic one could find here, most of all this stuff is the same and it is quite understandable why.
In the future you may find that asking simpler level questions on 997/GT3 forum do work out better. still, there are a lot of great people here on this forum whose input is pretty invaluable on many topics, so, as usual in life - there are no perfection in anything.
you just got to grow a pretty thick skin and try not to take most of all this stuff too seriously/personal.
In the future you may find that asking simpler level questions on 997/GT3 forum do work out better. still, there are a lot of great people here on this forum whose input is pretty invaluable on many topics, so, as usual in life - there are no perfection in anything.
you just got to grow a pretty thick skin and try not to take most of all this stuff too seriously/personal.
03-10-2011, 01:54 PM
#24
Race Car
Thread Starter
it is a pretty typical sample of a response here - people who do this stuff for 10+ years have their own interests in pretty different areas and get easily annoyed when stuff they have no interest in gets repeatedly surfaced up by people who only start on their hobbies. as I lurk around those forums for last 3 years there is hardly any principally new topic one could find here, most of all this stuff is the same and it is quite understandable why.
In the future you may find that asking simpler level questions on 997/GT3 forum do work out better. still, there are a lot of great people here on this forum whose input is pretty invaluable on many topics, so, as usual in life - there are no perfection in anything. you just got to grow a pretty thick skin and try not to take most of all this stuff too seriously/personal.
In the future you may find that asking simpler level questions on 997/GT3 forum do work out better. still, there are a lot of great people here on this forum whose input is pretty invaluable on many topics, so, as usual in life - there are no perfection in anything.
you just got to grow a pretty thick skin and try not to take most of all this stuff too seriously/personal.I did a search looking for information on tire pressures for ContiSport 3 tires and found nothing.
I have a very thick skin. I just don't suffer fools gladly......
Scott
03-10-2011, 05:55 PM
#26
Race Car
Thread Starter
Scott
03-10-2011, 06:29 PM
#27
[QUOTE=Bob Rouleau;8342615]Aim for 36 lbs F, 38 lbs Rear when HOT. Start at 32 F 34 R cold and check when you hit the pits after the session. You will probably have to bleed out some air to hit the target pressure. Never let the rears get over 40 - the rear of the car will be loose.
This is the short answer and it is the same as mine. Bob is experienced
and correct. hot 37-38 rear 36-37 front try for 2lbs less in front. The amount of pressure that one gains from cold tires to hot tires is different for each driving style or driver.
If you want to run 42-44 hot rear and 38-41 hot front then the tires and handling will feel fantastic and crisp. But it will also be slower and very greasy if you push the limits of grip to (slidding a little.)
This is the short answer and it is the same as mine. Bob is experienced
and correct. hot 37-38 rear 36-37 front try for 2lbs less in front. The amount of pressure that one gains from cold tires to hot tires is different for each driving style or driver.
If you want to run 42-44 hot rear and 38-41 hot front then the tires and handling will feel fantastic and crisp. But it will also be slower and very greasy if you push the limits of grip to (slidding a little.)
03-10-2011, 07:37 PM
#28
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......"it makes much sense to sample the collective wisdom to help establish parameters and possibly obtain a reasonable place to start"......winders.
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It sure does. And I hope I didn't leave the impression I thought otherwise. Besides which, riffling through all the information is what I have most fun with.
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It sure does. And I hope I didn't leave the impression I thought otherwise. Besides which, riffling through all the information is what I have most fun with.
03-10-2011, 07:48 PM
#29
This is my experience, too. I always try to stay below 40
