1998 Chevrolet Cavalier Owner's Manual - Page 303

Uniform Tire Quality 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 to deep tread, winter-type snow tires, space-saver or temporary use spare tires, tires with nominal rim diameters of 10 to inches 12 (25 to 30 cm), or to some limited-production tires. While the tires available General Motors passenger on 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. in driving habits, service practices and differences in road characteristics and climate. Traction -- A, B, C The traction grades, from highest to lowest, are B, and A, C, and they represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces asphalt and concrete. of A tire markedC may have poor traction performance. Warning: The traction grade assigned to this tire based is on braking (straight ahead) traction tests and does not include cornering (turning) traction. Temperature -- A, B, C Treadwear The treadwear grade is comparative rating based a on the wear rateof the tire when tested under controlled conditions on a specified government test course. For example, a tire graded would wear one anda half 150 (1 1/2) times as well on the government course as a tire graded 100. The relative performance tires depends of upon the actual conditionsof their use, however, and may depart significantly from the norm to variations due The temperature grades are (the highest),B, and C, A representing the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions ona 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 levelperformance of which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard 109. Grades No. B and A represent higher levels performance on the of laboratory test wheel than the minimum required by law. 6-45