1993 Chevrolet Lumina Owner's Manual - Page 231

The following information relates the to system developedby the United States National Highway Traffic Safety Administration which grades tires by treadwear, traction and temperature performance. (This applies onlyto vehicles soldin theUnited States.) The temperature grades A (the are highest), B, and C, representing the tire's resistanceto the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor Traction-A, B, C laboratory test wheel. Sustained high The traction grades, from highest to temperature can causethe material of lowest are: A,B, and C. They represent the tire to degenerate and reduce tire Treadwear the tire's abilityto stop on wet life, and excessive temperature can lead a The treadwear grade is comparative pavement as measured under controlled to sudden tire failure. The grade C rating basedon thewear rate of the tire conditions on specified governmenttest corresponds to a levelof performance when tested under controlled surfaces of asphalt and concrete. A tire which all passenger car tires must meet conditions on a specified government marked C may have poor traction under the Federal Motor Vehicle Safety test course. For example, a tire graded performance. Standard No. 109. Grades B and A 150 would wear oneand a half (1%) represent higher levelsof performance times as well on thegovernment course Warning: The traction grade assigned to this tire is basedon braking (straight- on the laboratory test wheel than the as a tire graded100. The relative minimum requiredby law. ahead) traction tests and does not performance of tires dependsupon the include cornering (turning) traction. actual conditions of their use, however, and may depart significantly from the norm due to variations in driving habits, service practicesand differences in road characteristics and climate. Uniform Tire Quality Grading Temperature-A, B, C