Cold Tire Pressure
Thread Starter
Instructor
Joined: May 2007
Posts: 148
Likes: 0
From: Franklinville New Jersey
Cold Tire Pressure
I haven't looked hard enough at the door sticker that tells the cold tire inflation pressure so if this is answered there, my apologies.
Since the pressure insde a fixed volume is temperature dependent, at what temperature (ideally) should cold tire pressure be measured. Tire pressure measured on a 50 degree morning before sunrise will be different from the pressure measured with the car sitting in an aspalt parking lot or driveway on a sunny 90 degree day (three to five PSIG).
My car seems to be extremely sensitive to tire pressure and I would like to get this close to right
Since the pressure insde a fixed volume is temperature dependent, at what temperature (ideally) should cold tire pressure be measured. Tire pressure measured on a 50 degree morning before sunrise will be different from the pressure measured with the car sitting in an aspalt parking lot or driveway on a sunny 90 degree day (three to five PSIG).
My car seems to be extremely sensitive to tire pressure and I would like to get this close to right
Team Owner
Joined: Apr 2005
Posts: 35,731
Likes: 148
From: Northern NYs Adirondack Mountains,http://www.visitsacandaga.com.
I do mine in the morning aftewr the car has sat all night.OBTW there have been a few threads abou the accuracy of the system.
My system (and a lot of others ) is ALWAYS a couple pounds higher than the good digital gage I use to set tire pressure. Not a problem if you know the difference is there, you just allow for it.
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
i've always taken 'cold' to simply refer to, before the car is used and heat has been built up in the tires from road use.
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 25
From: Austin Texas
"COLD" to Chevy means ambient air temperature. 30#'s if it's 30° or 90°. you have to add air in cold temps and release air in high temps. So far Chevy doesn't have Automatic Tire Air Pressure Regulators.
(and if they did it would be a $1295 option with a $200 a year charge to keep it activated.)
(and if they did it would be a $1295 option with a $200 a year charge to keep it activated.)
Drifting
Joined: Jun 2005
Posts: 1,837
Likes: 4
I use the seasonal mean low temperature for "cold". The National Weather Service publishes that information, but you probably know about how cold it is in the morning where you live anyway.
Around here, its about 30 degrees in the winter and 60 degrees in the summer, I don't bother with finer increments than that. This corresponds to about 3 PSI difference, so I put some air in in the spring and let some out in the fall.
Best thing to do is set them first thing in the morning, before the sun has shone on them. If need be, adjust for the current temperature at a rate of 1 PSI per 10 degrees F - that is to say, if your normal morning low is 60 degrees F but its 50 that morning set them to 1 PSI lower than your nominal value.
Around here, its about 30 degrees in the winter and 60 degrees in the summer, I don't bother with finer increments than that. This corresponds to about 3 PSI difference, so I put some air in in the spring and let some out in the fall.
Best thing to do is set them first thing in the morning, before the sun has shone on them. If need be, adjust for the current temperature at a rate of 1 PSI per 10 degrees F - that is to say, if your normal morning low is 60 degrees F but its 50 that morning set them to 1 PSI lower than your nominal value.
Le Mans Master
Joined: Sep 2004
Posts: 5,707
Likes: 4
From: Los Angeles
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Race Director
Joined: Aug 2000
Posts: 10,649
Likes: 31
From: Central Florida
Getting good mileage from these expensive runflats involves setting the cold psi to 30 and keeping an eye on it. Requires tinkering with seasonal temp fluctuation. I try to keep the normal hot psi at no more than 34.
Remaining in this 30C-34H range requires me to tweak the valve steams a couple times a month.
Hard to find free air at gas stations these days. Only one still has it in my area.
Ranger
Remaining in this 30C-34H range requires me to tweak the valve steams a couple times a month.
Hard to find free air at gas stations these days. Only one still has it in my area.
Ranger
Race Director
Joined: Jun 2002
Posts: 12,198
Likes: 15
From: Columbia MD
Getting good mileage from these expensive runflats involves setting the cold psi to 30 and keeping an eye on it. Requires tinkering with seasonal temp fluctuation. I try to keep the normal hot psi at no more than 34.
Remaining in this 30C-34H range requires me to tweak the valve steams a couple times a month.
Hard to find free air at gas stations these days. Only one still has it in my area.
Ranger
Remaining in this 30C-34H range requires me to tweak the valve steams a couple times a month.
Hard to find free air at gas stations these days. Only one still has it in my area.
Ranger
Set mine at 30psi cold after car has sat overnight, regardless of ambient temp.
Race Director
Joined: Jun 2002
Posts: 12,198
Likes: 15
From: Columbia MD
I haven't looked hard enough at the door sticker that tells the cold tire inflation pressure so if this is answered there, my apologies.
Since the pressure insde a fixed volume is temperature dependent, at what temperature (ideally) should cold tire pressure be measured. Tire pressure measured on a 50 degree morning before sunrise will be different from the pressure measured with the car sitting in an aspalt parking lot or driveway on a sunny 90 degree day (three to five PSIG).
My car seems to be extremely sensitive to tire pressure and I would like to get this close to right
Since the pressure insde a fixed volume is temperature dependent, at what temperature (ideally) should cold tire pressure be measured. Tire pressure measured on a 50 degree morning before sunrise will be different from the pressure measured with the car sitting in an aspalt parking lot or driveway on a sunny 90 degree day (three to five PSIG).
My car seems to be extremely sensitive to tire pressure and I would like to get this close to right
Melting Slicks
Joined: Jun 2006
Posts: 2,208
Likes: 1
I've used 32psi on every car I've owned, and do on the C6. Cold, I see 31 then quickly to 32 on the rr, 32 on the others. Hot, they go to 36-37 when driving, shall we say, quickly. If they go over 37 hot in the summer, I'll lower to 31 cold, otherwise this gets me best tire wear and still excellent handling. 
Burning Brakes
Joined: Aug 1999
Posts: 1,160
Likes: 6
Cruise-In II Veteran
I have kept my run flats at 28 psi cold for years. I have been getting 20,000 - 25,000 miles from my tires. When I kept them at 30 psi, I found the center of the tire wore faster. I remember reading the 28 psi tip on Corvette Forum many years ago. YMMV.
Team Owner
Joined: Oct 2004
Posts: 27,420
Likes: 64
From: San Clemente CA
At 12,000 miles I noticed my rear tires were waring in the center. I have since lowered the rears to 28 and hope it corrects the problem. I had the alignment check and the rear was OK but the fronts were toed in and wearing on the outside.
Le Mans Master
Joined: May 2005
Posts: 6,648
Likes: 808
From: FORT LAUDERDALE FL
i have never had a problem doing this. hot they run up to 31-32 - perfect.
Racer
Joined: Apr 2007
Posts: 279
Likes: 0
A good rule of thumb is 1 psi + or - for every 10 degrees above or below 70 degrees. Example: if it's 80 degrees outside and your cold tire pressure should be 30 psi (cold/70 degrees) then, at 80 degrees it should be reading 31 psi. At 60 degrees outside, 29 psi. Check the pressure when the tires are "cold" meaning not driven on for at least 3 hours and not sitting in the sun. I know everyone has their opinion on how they do it but this is how I do mine. Learned it from a very experienced EVOC instructor who had extensive knowledge about vehicles and tires. I have never had any issues with tire wear or anything else.
Moderator
Joined: Dec 2002
Posts: 40,877
Likes: 4,327
From: Lakewood Ranch, FL
My tpms and digital gage read pretty much the same.
