1997 Chevrolet Astro Owner's Manual - Page 303

1 /r\ CAUTION: Mixing tires could cause to lose control while you driving. If you mix tires of different sizes or types (radial and bias-belted tires), the vehicle may not handle properly, and could have a crash. you Using tires of different sizes may also cause damage to your vehicle. Be sure to use the all same size and type tires on wheels. It's all right to drive with your compact spare, vehicle. though. It was developed for use on your car tires. The Uniform Tire Quality Grading system does not apply to deep tread, winter-type snow tires, space-saver or temporary use spare tires, tires with nominal rim diameters of 10 to 12 inches(25 to 30 cm), or to some limited-production tires. While the tires available on General Motors passenger cars and light trucks may vary with respect to these grades, they must also conform to Federal safety requirements and additional General Motors Tire Performance Criteria (TPC) standards. Treadwear The treadwear grade is acomparative rating based on the wear rate of the tire when tested under controlled conditions on a specifiedgovernment test course. For example, a tire graded 150 would wear one and a half (1 1/2) times as well on the government course as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics and climate. Uniform TireQuality Grading The following informationrelates to the system developed by the United States National Highway Traffic Safety Administration,which grades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.) The grades are molded on the sidewalls of most passenger 6-47