2007 Saab 9-3 Owner's Manual - Page 243

Car care certain that all wheel nuts are properly tightened. See page 258. 243 Flat spotting All tires get hot, especially on long journeys or when the car is driven hard. After the car has been parked with hot tires and the tires have cooled down, a flat spot can form in the tire, where it is in contact with the ground. The same can occur if the car has not been moved for a long time. Flat spots can cause vibration that can be felt through the steering wheel, similar to that experienced when the wheels need balancing. Flat spots of this type disappear once the tires get hot again, usually after 10-15 miles (20-25 km) of driving at cruising speed. If the outdoor temperature is low it takes a longer distance. When It Is Time for New 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. You need a new tire if any of the following statements are true: • 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. • 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 or location of the damage. WARNING Rust or dirt on a wheel, or on the parts to 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 the vehicle. In an emergency, you can use a cloth or a paper towel to do this; but be sure to use a scraper or wire brush later, if you need to, to get all the rust or dirt off. See "Changing a tire" on page 257.