Tire Pressure

"A suburban mother's role is to deliver children obstetrically once, and by car forever after."~Peter De Vries

Last night as I was driving home I thought, “I should really check my tire pressure.” My wife’s car is newer and the dashboard has a warning light for low tire pressure. My car is not so smart and it’s been awhile since the pressure was checked.

Next to the brakes, the tires are the most important safety devices on a car. Incorrect tire pressure will compromise cornering, braking and stability, and lead to tire failure (i.e. a blow-out). Incorrect tire pressure also will affect your comfort, fuel economy and tire life.

If tire pressure is too high, then less of the tire touches the ground and your car will have more road bounce, have less traction and a longer stopping distance. If tire pressure is too low, then too much of the tire touches the ground, which increases friction, lowers your gas mileage, wears tires prematurely, and overheats tires leading to tread separation.

Tire pressure should be checked at least monthly (some say weekly). It’s not unusual to lose 1 psi per month. Even if there is no leak, the pressure will change with air temperature. Tire pressure decreases by about 1 pound per square inch (psi) for every 10-degree drop in outside air temperature. If your tire was just right in July at 80 degrees outside, it could be dangerously 10 pounds under inflated in January at minus 20 degrees.

The psi number listed on the tire itself is the maximum allowable air pressure. Don’t use this! Instead look on the edge of the driver’s door for the recommended pressure for your car. If there’s no sticker on the door, you can usually find the specs in the owner’s manual. Most passenger cars will recommend 32 to 35 psi.

Bottom Line

Check your tire pressure monthly. Check all four tires and your spare while the tires are cool, that means after driving only a few miles to reach a gas station, not after hours of driving.

Web Resources

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1
http://www.michelinman.com/tire-care/tire-saving-tips/air-pressure-tips/
http://cars.cartalk.com/content/advice/tirepressure.html