1993 Cadillac Seville Owner's Manual - Page 326

Deadwear The treadwear grade is a comparative rating based on wear rate of the the tirewhen tested under controlled conditionson a specified government test course. For example,a tire graded 150 would wear one and a half (1 1/2) times as well on the government course asa tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however,and may depart significantly fromthe 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 abilityto stop on wet pavement as measured under controlled conditions on specified governmenttest surfaces of asphalt and concrete. A tire marked C may havepoor traction performance. Warning: The traction grade assigned to this tire is based on braking (straight-ahead) traction tests and does not includecornering (turning) traction. - Temperature A, B, C The temperaturegrades are A (the highest), B, and C, representing the tire's resistanceto thegeneration of heat and its abilityto dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can causethe material of the tire to degenerate and reduce tire life, and excessive temperature can leadto sudden tire failure. The grade C corresponds to a level of performance which all passenger tires must meet under the Federal Motor Vehicle car Safety Standard No. 109. Grades B and A represent higher levelsof performance on thelaboratory test wheel than the minimum required by law. Warning: The temperature grade for this tire is established for a tire that is properly inflated and overloaded. Excessivespeed, underinflation, not or excessive loading,either separately or in combination, can cause heat buildup and possible tire failure. Those grades are molded on the sidewalls of passenger car tires. - 312