1998 Buick Regal Owner's Manual - Page 310

When rotating your tires, always use the correct rotation pattern shown here. Don't includethe compact sparetire in your tire rotation. After the tires have been rotated, adjust the front and rear inflation pressures as shown on the Tire-Loading Information label. Make certain that all wheel nuts are properly tightened. See "Wheel Nut Torque" in the Index. When It's Time for New Tires 1 1 One way to tell when it's time for new tires is to check thetreadwear indicators, which will appear when your tires have only 1/16 inch (1.6 mm) or less of tread remaining. Rust or dirton a wheel, or on the parts to which it is fastened, can make wheel nuts become loose after a time. The wheel could comeoff and cause an accident. When you change a wheel, remove any rust or dirt from places where the wheel attaches to the vehicle. In anemergency, you can use a cloth or a paper towel to do this; but be sure to a scraper orwire brush later, if you use need to, to get all the rust or dirt (See off. "Changing a Flat, Tire" in the Index.) You need a new tire if any of the following statements are true: 0 You can see the indicators at three or more places around the tire. You can see cord or fabric showing through the tire's rubber. The tread or sidewall is cracked, cut or snagged deep enough to show cord or fabric. 0 0 6-46