2001 Chevrolet Tracker Owner's Manual - Page 282

Uniform Tire Quality Grading The following information relates to system the developed bythe United States National Highway Traffic Safety Administration, which grades by tires 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 car tires. The Uniform Tire Quality Grading system does not apply to deep tread, winter-type snow tires, tires space-saver or temporary use spare tires, with nominal rim diameters of10 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 Federal safety to requirements and additional General Motors Tire Performance Criteria ( P C ) standards. Treadwear The treadwear gradeis a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded would wear one and 150 a half (1112) times as well on the government course as a tire graded100. The relative performanceof tires depends upon actual conditionsof their use, the however, and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics and climate. Traction -- A, B, C The traction grades, from highest tolowest, are A,B, and C, and they representthe tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces asphalt of and concrete.A tire marked C may have poor traction performance. Warning: The traction grade assigned to this is based tire on braking (straight ahead) traction tests and does not include cornering (turning) traction. 6-45