Tire Pressure
Drifting
Joined: Sep 2019
Posts: 1,913
Likes: 1,957
From: Colo Spgs, CO
It's hard to get around PV=nRT. Dropping cold tire pressure a couple of psi will mitigate the rise, without any appreciable risk to the tires. Another option is to inflate with nitrogen, which provides more stable pressure over time/temp.
Drifting
Joined: Sep 2019
Posts: 1,355
Likes: 635
From: St. Louis
Nitrogen is subject to the same PV=nRT physics as air (which is mostly nitrogen anyway) so nitrogen is not actually a solution to this problem.
Drifting
Joined: Sep 2019
Posts: 1,913
Likes: 1,957
From: Colo Spgs, CO
According to NHTSA, air escapes tires more quickly than nitrogen, meaning more frequent adjustment is required. Nitrogen used to inflate tires is delivered "dry," meaning it contains less water vapor than air from a run-of-the-mill compressor. The presence of water vapor in a tire increases its pressure variance with temperature over that of one filled with "dry" gas. All of this points to nitrogen providing more stable tire pressures, requiring less adjustment, over time. Nitrogen is, however, no substitute for regular/proactive tire care/maintenance nor will it eliminate the problem. The question is whether nitrogen's arguably marginal benefits are worth its cost, which is a case of YMMV.
Melting Slicks
Joined: May 2005
Posts: 3,461
Likes: 161
From: Las Vegas Nevada
St. Jude Donor '08
With these low profile & next to no rubber between road & wheel, less air in tire means less stiff rubber to absorb some of the shock going over expansion joints, potholes, etc. Rubber with less air pressure will allow tire to flex more which COULD lead to sidewall cracking also. JMO
Le Mans Master
Joined: Dec 2000
Posts: 5,348
Likes: 3,319
The tire is part of the suspension. A softer tire absorbs a bit more of the bumps, just like a softer spring.
But, as a practical matter, tire pressures within 10% of each other are going to be very similar.
But, as a practical matter, tire pressures within 10% of each other are going to be very similar.
Drifting
Joined: Sep 2019
Posts: 1,913
Likes: 1,957
From: Colo Spgs, CO
It's unlikely a <10% pressure reduction in a tire that's designed to handle ZERO PRESSURE (i.e., RUN-FLAT) conditions will cause any serious problems. Tires are rubber that's supposed to be flexible and pressures increase as the tires warm-up.
Last edited by NortonCO; Aug 12, 2020 at 11:31 PM.
Race Director
Joined: Jun 2005
Posts: 10,909
Likes: 2,701
From: Phila Suburbs 2023 C8 & 2013 650ix
I hate repeating myself but i've got around 80,000 miles of experience with the tires on the base C6 & C7 combined. The tires on the base cars are the same size. And I keep records of tread depth across the width of the tire as mileage accumulates. My experience says that 30 hot is the best pressure for even wear across the width of the tire. So whatever cold pressure gives me 30 psi when hot, is what I use. This is so easy to monitor with the TPS system that we have.
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Safety Car
Joined: May 2000
Posts: 4,827
Likes: 351
From: Albuquerque NM
GM's suggested 30 PSI cold is a good starting point for most folks. The "best" air pressure is like the "best" suspension settings, it varies with the driver and his style. It sounds like Walt White Coupe's driving style matches what the designer's had in mind. More agressive cornering (or less) or harder launches may work better with higher or lower starting pressures. Find what works best for you. FWIW I don't think 2 to 3 PSI changes will make much difference on the street.
Intermediate
Joined: Sep 2019
Posts: 46
Likes: 32
From: Naples, FL
I live in Vegas also and was wondering the same thing. I'm sure you've noticed that our excessive summer heat makes tires hard as rocks after around 5 years. So I wonder if it would be a bad idea to run lower pressure for fear of sidewall cracking.
I just replaced tires on my 2015 Honda (only had 17000 miles on them) and the difference in ride is remarkable. I knew they were getting hard by the lack of traction. I don't know how old your tires are but I think the stiffness once they harden will be the real danger to your wheels.
I just replaced tires on my 2015 Honda (only had 17000 miles on them) and the difference in ride is remarkable. I knew they were getting hard by the lack of traction. I don't know how old your tires are but I think the stiffness once they harden will be the real danger to your wheels.
Safety Car
Joined: Oct 2015
Posts: 4,128
Likes: 616
From: St Louis Area IL
I was wondering about lower than 30psi. I live in Las Vegas, and it sure gets hot here in the summer. With the tire pressure set at 30psi cold, after driving in this heat, the pressure can go up to 35psi. I have a GS, and know about the wide body wheel problems. I was thinking about setting the cold pressure at 28psi, so it will go up to about 32 or 33psi while driving. What do you people think?
The only place you need to play with the psi is when you are doing a trackday, or racing. Then it is personal preference where you like it for a certain feel while on the track. I would just set it for 30 psi when cold and leave it at that. Your choice of course.
Melting Slicks
Joined: Jul 2011
Posts: 2,055
Likes: 864
From: So Cal
We keep our Z06 in Palm Desert and the temps lately have been averaging 108F to 114F. One day was 121F. We use 30 psi cold. However, if the OAT is 110F, your “cold” tire pressure will likely indicate 32F or even 33F if the tires were inflated on a more normal day where the OAT was maybe 80F or less.
On big airplanes the tire pressure is set cold and never increased or decreased when flying in Alaska at -30F or in Arizona at 120F. I tend to think that all these tire engineers have this kinda figured out for street use.
On big airplanes the tire pressure is set cold and never increased or decreased when flying in Alaska at -30F or in Arizona at 120F. I tend to think that all these tire engineers have this kinda figured out for street use.
Last edited by B747VET; Aug 13, 2020 at 10:32 PM.
Team Owner
Joined: Sep 2000
Posts: 25,015
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From: Far NW 'burbs of Chicago
St. Jude Donor '13
Last edited by Gearhead Jim; Aug 14, 2020 at 02:40 PM.
Safety Car
Joined: Oct 2015
Posts: 4,128
Likes: 616
From: St Louis Area IL
Burning Brakes
Joined: Oct 2017
Posts: 1,230
Likes: 467
From: Colorado
Hey High-Altitude guys - remember where you're at. Significant changes in altitude affects tire pressures. I'm at 6100' and @Discount Tire pumps me to 33psi warm. (Just chiming in...carry on)
Drifting
Joined: Sep 2019
Posts: 1,355
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From: St. Louis