1995 GMC Sonoma Owner's Manual - Page 261

When it's Time for New Tires Tread Wear Indicators One way to tell when it's time for new tires is to check the treadwear indicators, which will appear when your tires have only 1/16 inch (1.6 mm) or less of tread remaining. You need a new tire if You can see the indicatorsat three or more places around the tire. 0 0 You can see cord or fabric showing through the tire's rubber. The tread or sidewall is cracked, cut or snagged deep enough toshow cord or fabric. The tire has a bump, bulge or split. The tire has a puncture, cut,or other damagethat can't be repaired well because of the size or location of the damage. Buying New Tires To find out what kind and size of tires you need, look at the Certificationflire label. The tires installed on your vehicle when it was new had a Tire Performance Criteria Specification (TPC Spec) number on each tire's sidewall. When you get new tires, get ones with that same TPC Spec number. That way, your vehicle will continue to havetires that are designedto give proper endurance, handling, speed rating, traction, ride and other things during normal service on your vehicle. If your tires have an all-season tread design, the TPC number will be followed by an "MS" (for mud and snow). If you ever replace yourtires with those not having a TPC Spec number, make sure they are the same size, load range, speed rating and construction type (bias, bias-belted or radial) asyour original tires. 6-43