1998 GMC Safari Owner's Manual - Page 309

Uniform Tire Quality Grading Tkeadwear The treadwear grade is comparative rating based on a The following information relates the system to the wear rate of the tire when tested under controlled developed by the United States National Highway conditions ona specified government test course. For Traffic Safety Administration, which grades by tires example, a tire graded 150 would wear one anda half treadwear, traction and temperature performance.(This (1 1/2) times as well the government course a tire on as applies onlyto vehicles soldin the United States.) The graded 100. The relative performance of tires depends grades are molded on the sidewalls of most passenger of car tires. The Uniform Tire Quality Grading system does upon the actual conditions their use, however, and may depart significantly from the norm due to variation not apply to deep tread, winter-type snow tires, in driving habits, service practices and differences in space-saver or temporary use spare tires, tires with road characteristics and climate. nominal rim diametersof 10 to 12 inches (25 to30 cm), or to some limited-production tires. lkaction A, B, C While the tires availableon General Motors passenger The traction grades, from highest to lowest, are A, B, cars andlight trucks may vary with respect to these and C, and they represent the tire's ability to stop on wet grades, they must also conform to Federal safety pavement as measured under controlled conditions on requirements and additional General Motors Tire specified government test surfaces asphalt and concrete. of Performance Criteria (TPC) standards. A tire marked C may have poor traction performance. Warning: The traction grade assigned this tire is based to on braking (straight ahead) traction tests and does not include cornering (turning) traction. -- 6-47