1998 Pontiac Bonneville Owner's Manual - Page 297

Treadwear The treadwear grade is a comparative rating based on the wear rate the tire when tested under controlled of conditions on a specified government test course. For example, a tire graded 150 would wear and a one half (1 1/2) times as well on the government course as a tire graded The relative performance tires 100. of of depends upon the actual conditions their use, however, and may depart significantly from the norm due to variations in driving habits, service practices and differencesin road characteristics and climate. Traction Temperature -- A, B, C The temperature grades are (the highest),B, and C, A representing the tire's resistance to the generation of heat and its ability dissipate heat when tested under to controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tireto degenerate and reduce tire life, and excessive temperature can lead sudden tire failure. to The gradeC corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard 109. Grades No. B and A represent higher levels of performance the on laboratory test wheel than the minimum required by law. Warning: The temperature grade for tire is this established for a tire thatproperly inflated and not is overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure. -- A,B,C The traction grades, from highest lowest, areA, B, to and C, and they represent the tire's ability to stop on wet pavementas measured under controlled conditions on specified government test surfaces of asphalt and concrete.A tire markedC 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. 6-46