2003 GMC Sonoma Owner's Manual - Page 328

Inflation -- Tire Pressure The CertificationlTire label, which is on the driver's door edge, above the door latch, shows the correct inflation pressures fur your tires when they're cold. "Cold" means your vehicle has been sitting for at least three hours or driven no more than 1 mile (1.6 km). When to Check Check your tires once a month or more. Also, check the tire pressure of the spare tire. If you have a compact spare tire, it should be at 60 psi (420 kPa). Notice: Don't let anyone tell you that underinflation or overinflation is all right. It's not. If your tires don't have enough air (underinflation), you can get the following: Too much flexing 0 How to Check Use a good quality pocket-type gage to check tire pressure. You can't tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they're underinflated. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. Too much heat Tireoverloading 0 Bad wear Bad handling 0 Bad fuel economy If your tires have too much air (overinflation), you can get the following: 0 Unusual wear Badhandling Roughride 0 Needless damage from road hazards 5-65