1996 Pontiac Firebird Owner's Manual - Page 291

Uniform TireQuality Grading The following information relates 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 car tires. The Uniform Tire Quality Grading system does not apply todeep 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 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. Traction -- A, B,C The traction grades, from highest to lowest,are A, B, and C, and they represent the tire's ability to stop on wet pavement as measured under controlled conditionson specified government test surfaces of asphalt and concrete. A tire marked C may have poor traction,performance. Warning: The traction grade assigned to this tire is based on braking (straightahead) traction tests and does not include cornering (turning) traction. Temperature -- A, B,C The temperature grades are A (the highest), B, and C, I , The treadwear grade is a comparative rating based on the wearrate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and a h l af (1 112) times as well on the government course as a tire graded 100. The relative performance of tires depends representing the tire's resistance to thegeneration of heat and its ability to dissipate heat when tested under controlled co'nditionson a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performame which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. 6-50