1995 Oldsmobile Silhouette Owner's Manual - Page 299

Treadwear The treadwear grade a comparative rating based on is the wear rate of the tire when tested under controlled conditions on 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 as a tire graded 100. The relativeperformance of tires depends upon the actual conditions of their use, however, and may depart significantlyfrom the norm due tovariations in driving habits, service practices differences in and road characteristics and climate. 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 to dissipateheat when tested under controlled conditionson a specified indoorlaboratory test wheel. Sustainedhigh temperature can cause the material of the tire to degenerate reduce tirelife, and and excessive temperaturecan lead to sudden tire failure. The gradeC corresponds toa level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety StandardNo. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. Warning: The temperature grade for tire is this established fora tire that is properly inflated and not overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure. These grades are molded on the sidewalls of passenger car tires. - Traction A, B, C The traction grades, from highest to lowest are: B, A, and C . They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfacesof 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. - 6-39