1996 Chevrolet Astro Owner's Manual - Page 253

Uniform Tire Quality Grading The following information relates to the system developed by the United States NationalHighway Traffic Safety Administration which grades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.) Treadwear The treadwear grade a comparative rating based on the wear rate of the is tire when tested under controlled conditionson a specified government test course. For example, a tire graded 150 would wear one and a half (1 112) times as wellon the government course as a tire graded 100. The relative of performance of tires depends upon the actual conditions their use, however, and may depart significantlyfrom the norm due to variationsin 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 stopon 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 isbased on braking (straight-ahead) traction tests and does not include cornering (turning) traction. Temperature - A, 9, C The temperature grades are (the highest),B, and C, representing the tire's A resistance to the generation heat and its ability to dissipate heatwhen of tested under controlled conditionson a specified indoor laboratory test wheel. Sustainedhigh temperature can cause thematerial of the tire to degenerate and reduce tire life, excessive temperaturecan lead to and 6-45