Just wondering what happens if you check the tire pressure when the car is not completely cold. Will the tires blow up or something? My husband checked mine after the car had been sitting for about 45 minutes tonight. All the tires were at 25 psi. He added air to the door panel's recommendation of 35 psi. My Mini has 15 inch wheels with Contis on it. When I set out tomorrow will the tire pressure sensor come on? Will the tires all go flat because the car wasn't completely warm? You guys have me scared to death.

 

You'll be fine - the tires just might need a little more air. If he filled them to 35 psi when they were slightly warm, then they will be a lower pressure when cold. After 45 minutes, though, the tires should be cooling off pretty well.

You may want to reset the tire pressure monitoring system. After you've started the car, press and hold the tire pressure monitoring system button until the tire pressure light comes on. Then, drive normally and the system will reset itself and the light will go off.

Don't worry - you'll be OK!

 

They should be dormant for 4 hours -the heat from rolling makes your "cold pressure" falsely high. Check them tomorrow before your drive, and you'll see what I mean.

If you have to move the car to add air, just take the pressures cold - as add the amount of pounds to the warm tire it would have taken to be @ pressue cold.

Aka 35 PSI required - Cold you have 31, you need to Add 4 lbs - You can add it when ever you want. Just check the pressure before adding, add the 4# you need .

Alex

 

My garage is usually about 10-15F warmer than outside in the cooler/cold
months (vise versa for warmer months) so it is never perfectly accurate.
i pump or let out air in them when I note the difference in temps between
inside the garage and outside.

It's good to have a thermometer in the garage and compare with
ambient outside temps from weatherchannel.

For every 10F of difference, I add/subtract 1psi of air.

Also when temps are in the 25-35F range, tires do not warm up
like it does in the summer time...so i also compensate by adding
even more air when its in the sub-zero temps. Basically, my
target hot pressure is about 38-40psi depending on what type of
driving I plan to do.

for my daily driver that sit outside, i just put in 33psi in the morning.
if the sun is out and shining on one side of the car, i usually notice
a 1-2psi difference between one side of the car and the other that is
shaded, so i compensate for that difference as well. pretty tricky
if you get picky.

 

wait-wait your supposed to check them cold. I've been checking them hot all these years.

Really, cold. Who would have guessed it. I thought you check them hot cuz thats the way you drive it.

 

Track rats look at hot pressures, and pressure uniformity across the tread. But these are typically in the 40s or so. But Kenchan, you should do your temp compensation with absolute temps. For a temp of 70 F, your at about 300 K. If you use 30 psi to make the math easy, that's 10 C per PSI, or 18 F.

Matt