1997 GMC Safari Owner's Manual - Page 303

Mixing tires could cause you to lose control while driving. If you mix tires of different sizes or types (radial andbias-belted tires), the vehicle may not handle properly, and you could havea crash. Using tires of different sizes may also cause damage toyour-vehicle.Be sure touse the same size and type tires onall wheels. It's all right to drive your compact spare, with though. It was developedfor use on your vehicle. car tires. The Uniform Tire Quality Grading sysrem does not apply to deep tread, winter-type snow tires, space-saver ortemporary use spare tires, tires with nominal rim diametersof 10 to 12 inches(25 to 30 cm), or tosome limited-production tires. While the tires available General Motors passenger on cars and light trucks may vary withrespect to these grades, they must also conform to Federalsafety requirements and additional General Motors Tire Performance Criteria (TPC) standards. 'beadwear The treadwear grade is a comparative rating based on the wear rate of the tirewhen tested under controlled conditions on a specified government test course. For example, atire graded 150 would wear one and a half (1 1/2) times as well on the government course as a tire graded 100. The relativeperformance of tires depends upon the actual conditionsof their use, however, and may depart significantly fromthe norm due to variations in driving habits, service practices and differences in road characteristics and climate. Uniform Tire Quality Grading The following information relates the system to developed by the United States NationalHighway Traffic Safety Administration, which grades tiresby treadwear, traction and temperature performance.(This applies only to vehicles sold in the United States.) The grades aremolded on the sidewallsof most passenger 6-47