1996 GMC Savana Van Owner's Manual - Page 268

A CAUTION: Rust or dirt a wheel, or on the parts to on which it is fastened, can make wheel nuts become loose after a time. The wheel could come off and cause an accident. When you change a wheel, remove any rust or dirt from places where the wheel attaches to thevehicle. In an emergency, can you use a cloth or a paper towel to do this; but be sure touse a scraper or wire brush later, if you rust or dirt (See off. need to, to get all the "Changing a Flat Tire" in the Index.) When It's Time forNew Tires 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. Some commercial truck tires may not have treadwear indicators. You need a new tire if any of the following statements are true: 0 0 0 0 You can see the indicators at three or more places around the tire. You can see cord or fabricshowing through the tire's rubber. The tread or sidewall is cracked, cut or snagged deep enough to show cord or fdbric. The tire has a bump, bulge or split. The tire has a puncture, cut or other damage that can't be repaired well because of the size orlocation of the damage. 6-44