ZoomOn43

Ok so question... you're to check and fill the tires at "while cold", I understand that. What I am trying to figure out is how do you compensate for ambient air temperature differences. If I check in the summer in the AM and say it is 75 deg out and set at 30psi. That would be different if it was 45 deg out and I set them to 30 psi right? Or does it matter as long as the tires are cold.

stevebz06

Just set the tire pressure and don't worry about the ambient temperature. Maybe an argument can be made for changing it depending on conditions, but I've never heard anybody make that claim. And the same for atmospheric pressure. The ambient pressure changes all the time also.

owc6

The party line is whatever the label inside the driver's door says as cold psi (for the vast majority of us that is 30 psi). That means before you go anywhere in the morning regardless of ambient temp: set them to that number. That's good advice which will yield good results.

In real life, as you have more miles on the car, you can use that as a gauge for what you really like them to be. I like them to be a little "overinflated", which means 33# to start. For me, that gives the handling I prefer, and perfectly even wear. I've never heard of anyone preferring "under inflating."

TEXHAWK0

No need to adjust them daily, but I do adjust my pressures for seasonal temperature changes.
As summer ends and the weather cools, if I see pressures starting to be 2 or 3 psi less than I normally run, I will adjust them back to the 30 psi target.
Better to be a little high, than consistently running lower pressure.

I have noticed that the front tires seem to run a pound or so higher due to engine temp, more braking, etc. so I have actually set the fronts to be a pound or two lower so when they come up to operating temperature, the fronts and rears are the same.

Foosh

The recommended inflation pressures are the same whether it's 90º or 20º. If you inflate to 30 psi in the summer, you'll find the pressures will drop usually about 10% or more once it gets cold. You'll need to add air to stay at 30 psi, and that's how you compensate for ambient temp.

DogTag-C7R

For daily driving I ALWAYS start at 32. Obviously not a good number at the track.

Patman

I like to check the tire pressures in all of my cars about once a month so as the weather cools off, I do need to add air in order to keep it at the correct pressure. Once it gets into the late fall I usually add an extra couple of psi as well since I know it'll get much colder in the winter and I want to make sure they aren't under inflated. (I agree with Texhawk, I'd rather be slightly high than too low)

Vetteman Jack

Just get the tires to 30 psi cold and you’ll be OK.

JerryU

Hmm, lots of comments but no direct answer! For every 10 degree F change the tire pressure changes ~1 psi!

It does take a while for the tire (air) to cool, which is why it's recommended to check first thing in the morning before driving. Remember the tires heat from internal and road friction when driving and those aluminum wheels are close to very hot brakes!

AORoads

You're right, Zoom, there is a difference in setting it at 45 or 75. But 30 is 30 at both temps, and that's what is listed as the pressure to use. As said above by others, if you set the pressure at 30 in 75 degree weather and drove the car somewhere and the ambient was 45, then a few of the posts above like Jerry's are correct, too: you would "lose" approx 1 lb. of pressure for each 10 degree drop in ambient. Not the tire's fault. So, at 45 ambient, your tire pressure would be about 27 cold (if you waited to check it when cold). That is also why several posts like Tex above say, when seasons change you need to adjust tire pressure accordingly (winter=increase; summer=decrease. both using a gauge, not a guess-timate).

shakinrock

The only add I have is even if you have not driven your car for hours, make sure the tires are not in direct sunlight. The set to whatever.

rmorin1249

Still curious why GM raised the recommended pressures in 2016 for the base cars to 35 psi(cold). Same tires as previous years. Some have said it was to try and increase mileage. What say you? I run 32 in mine.

CP

Blame this guy: Gay-Lussac

Harry2

I had the same problem yesterday, my Minneapolis temp was down to the mid fifties in the morning, I checked my OnStar app and found my vette tire pressures were down to 28 PSI which I confirmed with my digital pressure gauge. I took my Specialized bike pump out and it took 30 pumps to fill each wide GS tire back up to 30 PSI, after being driven they went back up to 33 PSI. In November when my vette goes into hibernation, I fill the pressure up to 35 PSI to cover the winter period when my attached garage will get down to about 30 degrees.

Fireeagle

Being from the Northeast, ambient temps do impact tire pressure. In the cold weather, you will lose 3 to 5 lbs, so i look for a cold morning in fall to bump them back up to 30 PSI. Get a good gauge also. I've found so many of the non-digital gauges to be off but my digitals will match the tire pressure reading inside the vette.

rodney123456

i have found i use the my chev app on phone first time and i update it the first time too i check the tire pressure it is up to 37 cold then when i update the pressure again in the app it is down to 35 on all tires anybody else having this

Custom Corvette Accessories

Inflate in the Winter
Deflate in the Summer

Regards
Chip

Widgeon5

And the same for atmospheric pressure. The ambient pressure changes all the time also.[/QUOTE]

Atmospheric pressure changes are all but negligible as they affect tire pressure; 1/4 psi most of the time and occasionally up to 1/2 psi.

The math: Sea level pressure is about 14.7 psi or 30.00 inches of mercury. Barometric pressure is seldom outside the range of 29.60 to 30.60 unless its a hurricane situation. 1.00 inch of mercury is about 1/2 psi.

davepl

He's the biggest proponent of filling your tires with nitrogen I take it?

Walt White Coupe

Gay-Lussac's Law is an ideal gas law where at constant volume, the pressure of an ideal gas is directly proportional to its absolute temperature. In other words, Gay-Lussac's Law states that the pressure of a fixed amount of gas at fixed volume is directly proportional to its temperature in kelvins.