1995 Chevrolet Suburban Owner's Manual - Page 336

Uniform lire Qualify Grading The following information relates to the system developed by the United States National Highway Traffic Safety Administration which grades tires only to by treadwear, traction and temperature performance. (This applies vehicles sold in the United States.) Treadwear The treadwear gradeis a comparative rating based on the wear rate of the tire when tested under controlled conditionson a specified government test course. For example, a tire graded 150 would wear one and a half ( I 1/2) times as well on the government course as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantlyfrom 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. They represent the tire's ability to stop on wet pavement as measured under controlled conditions on 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 (straight-ahead) traction tests and does not include cornering (turning) traction. Temperature - A, 6, C The temperature grades are A (the highest), B, and C, representing the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditionson 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 fdilure. The grade C corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. 6-59