Ok. My Daddy always told me to check tire pressure when the tires are cold. Just driving a half mile to the gas station air pump will raise the pressure. Yesterday I took the pressure in the driveway before starting off for work. 28 PSI all around. Then when I got to work (10 mile trip) they were at 32 PSI. I've read we are supposed to run 32 PSI, but should that be cold temp. or actual running temp? S 02's by the way, 18 degrees last night on my commute home. I'm not having a problem with them. Don't understand all the posts saying under 40 degrees they are deadly. The car does feel a little "light" though nowadays up on the highway on a cold night. Best Winter tires are Blizzaks?

 

Always check and adjust your tyre pressures when cold.
For this reason I always use a foot pump at home and my own calibrated gauge.

 

32psi cold is the recommendation. However, I will adjust to operating pressures of about 36 if I can and also tune for events like autocrosses and track...

 

When I used to run BFG R1s at autoXes, the company rep told me that the tire pressure recommendations are all based on cold temperatures. IOW, if your desired pressure is 32# and you measured your tires at 28# "cold", then noticed a jump to 32# when you arrived at the nearest air tank, you'd want to pump in an additional 4# (i.e., 32# + 4# = 36# "hot"). Theoretically, when you next check your tires cold (assuming no air loss) you'd notice that they are now 32# "cold." When in doubt, contact a tire rep at the factory or web site for the "official" line.

 

Hmmm, not sure if the heating is a linear function (i.e., 32# + 4# = 36# "hot") but is prolly close enough.

 

I'm no chemist, but Boyle's Law states that Pressure x Volume = a constant (assuming that temperature remains the same) and Charle's Law says that as temperature increases, volume increases. Ergo, I think that there may be a linear relationship between increasing temperatures and a relatively fixed volume (i.e., the tire), but what do I know?!?! Any chemists in the house???

 

Well, I've been know to muddy the water myself. Two substances on Earth that do now follow all others re:reaction to heat exist. All other materials expand when heated, and contract when cooled. Water expands with both heat and cold (ice), and rubber contracts with both (hold a match to a rubber and watch it shrivel). I'd call it Sir Loadstone's Law if I thought it would add some weight. Anyway, thanks to all. I bought a pump with attached guage and will be putting 32lbs. in it cold from now on.

 

LOL. nothing like over analyzing. Good solution.