Proper tire PSI

[sdguy]

Hi All,

I recently had my car serviced and noticed that my car rode a bit softer, as if the suspension had changed. Upon checking my tire pressure, I realized that it had been lowered to 32 psi. If I do recall, the reading was previously 40 psi all around, but I could be wrong. Currently I'm running Michellin Pilot Sport 18s.

What's the OEM reccomended psi for these tires? Also, should these ratings be applied differently on front and rear tires? The owner's manual has a large varience in the it's recommendations (32-43). My main concern is longevity of the tires.

Comments are appreciated.

[MarvelPhx]

Start with the sticker on the inside driver's door jamb. The recommendations are based on stock tires and how much load is in the car. So if it's 32-43, then 32 is minimum load, 43 if you are full of people and luggage. Never exceeed the max pressure on the side of the tire, but for general driving, 32-35 is fine. Higher if you drive hard.

[WOSBY]

My experience:

The recommended tire pressures are for tires that are COLD (sitting for at least 4 hours). Once you start driving a car, the friction of the tire against the pavement create's heat. This heat is transferred to the air inside the tire, which in turn increases the tire pressure by an additional 1 to 2 psi. The Dealer/tire manufacterer knows this when recommending the tire pressure! ALSO, for every 10 degree change +/- in air temperature, you tire pressure changes +/- 1 psi.

The problem is, when having your car serviced, they are opperating on limited time, and your tires dont have time to cool off. But they have to check it anyway. Now you've driven to the service department, your tires are warm, so when they check the pressure, it will appear high. So they lower it. You notice this as a softer ride when leaving the dealer.

Solution: Check and adjust your tire pressure yourself on a regular basis. Check them in the morning when they are cold. Your tires will wear more evenly and last longer.

wosby