1998 GMC Sonoma Owner's Manual - Page 294

Tire Inspection and Rotation NOTICE: (Continued) If your tires have too much air (overinflation), you can get the following: 0 Unusualwear 0 Badhandling 0 Roughride Needless damage from road hazards. When to Check Check your tires once a month or more. Also, check the tire pressure of the spare tire. Tires should be rotated every 6,000 to 8,000 miles (10 000 to 13 000 km). Any time you notice unusual wear, rotate your tires as soon as possible and check wheel alignment. Also check for damaged tires or wheels. See "When It's Time for New Tires" and "Wheel Replacement" later in this section for more information. The purpose of regular rotation is to achieve more uniform wear for all tires on the vehicle. The first rotation is the most important. See "Scheduled Maintenance Services" in the Index for scheduled rotation intervals. If you have a compact spare tire, it should be at 60 psi (420 Wa). 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.