1996 Pontiac Grand Prix Owner's Manual - Page 280

Uniform Tire Quality Grading The following information relates to the system developed by the United States National Highway Traffic Safety Administration, whichgrades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.)The grades are molded on the sidewalls ofmost passenger car tires. The Uniform Tire Quality Grading system does not apply to deep tread, winter-type snow tires, space-saver or temporaryuse spare tires, tires with nominal rim diameters of10 to 12 inches (25 to 30 cm), or to limited-production some tires. I . Treadwear The treadwear grade is a comparative rating based on the wear rateof the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and a half (1 1/2) times as well on the-governmentcourse as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantlyfrom the norm due to variations in driving habits, service practices and differences in road characteristics andclimate. 1