Correct tire pressure adjustment


#1

my car recommmend 32psi for all 4 tires, and 60 psi for the doughnut spare. currently where i live there can be a 50 degree difference between day and night temperatures. it can range from 45-50 lows to 95-100 highs. tire temperature goes up and down about 1 psi for every 10 degrees. what is the correct temperature to set these tires for. if i set them at 32 psi at 100, then they should only be 27 psi at 50. if i set them at 32 psi at 50 they should be 37 at 100.


#2

There is no great harm being done to overinflate your tires a little, but underinflation is bad, bad, bad! Heat buildup!! Heat is the tire killer.

So inflate at 32 psi at 50 and live with 37 at 100.


#3

That is certainly the way I would go too. But this can be tricky, and I have wondered about this kind of problem myself. E.g. what if the those tires are rated for 35psi max cold. Then they are beyond the tire’s max rating. What is the operating definition of “cold” for setting max pressures?

Here’s another e.g. - my van calls for 35psi all around. Like many passenger tires mine are rated for 35psi max cold. If I set them at 35psi in the morning at 50 degrees, then that afternoon it gets to 90, I am leaving my driveway with the tires at 39psi or so - which exceeds the tire’s max. How much room for error do you suppose goes into the manufacturer’s max pressure designations?


#4

That is a tough one. Your range is beyond what many people will find. I think I would go with the recommended 32psi adjusted to about 60 degrees. I would also tend to take it easy the first few miles in the morning as they tyres will be a little under inflated but they will be a little over by the afternoon. Don’t worry about the temperature in the tyres as that will be above the air temperature once you start driving and that is figured in to that original recommendation.

It might be interesting to contact the manufacturer ( Not the dealer ) and see what they say. Like everyone else here, we are doing some guessing SWAG maybe, but it is still guessing.


#5

There are many sources of this information, here’s one- http://www.tirerack.com/tires/tiretech/tirespecskey.jsp

Most sources cite the reference cold temp as around 60-65 deg F. The manufacturer has already accounted for the pressure rise due to temperature. If you set your tire pressure first thing in the morning, before any heating from driving or solar radiation for example, you should be all set.


#6

Set the pressure in the morning. The air dissipates throught the tire but it will take more than overnight to drop it that far IMOO.


#7

The car maker’s recommended pressure is 32 PSI, but I’d bet the tires can actually handle quite a bit more than that. Besides, the recommended pressure is cold, so what else can you do? They’ll pump up a bit during the day, but should be none the worse for wear.


#8

You’ll have to take my word for it, but many passenger car tires that say “Max pressure 35 psi” could easily have said “Max pressure 44 psi”. It’s a tire standards thing and the way different tire manufacturers read the government regulation. Interestingly the Michelin group (Michelin, Goodrich, Uniroyal) and a couple of asian manufacturers are the only ones who use 35 psi for S and T rated passenger car tires. Everyone else uses 44 psi. (BTW, this is the one of the few exceptions to the “Don’t exceed the max pressure on the sidewall” warnings.)


#9

i bought tires at sears 18 months ago. they were putting 35psi in when it called for thirty.they wore in the middle.if u over inflate your tires this will happen.they put new tires on .that was the problem.their computer was telling them 35psi.the manager agreedit was from overinflation.2002 montecarlo ss