1995 GMC Jimmy Owner's Manual - Page 285

Uniform Tire Quality Grading The following information relates to the system developed by the United States National Highway Traffic Safety Administration which grades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the UnitedStates.) Treadwear The treadwear grade is a comparative rating based on the wear of the rate tire when tested undercontrolled conditions on a specified government test course. For example, atire graded 150 would wear one and a half ( 1 1/ 2 ) times as well on the government course as atire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantly from 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 poortraction 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, ByC The temperature grades are A (the highest), B, and C, representing the tire's resistance to the generation of heat and itsability to dissipate heat when tested under controlled conditions on 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 failure. Thegrade C corresponds to a level of performance which all passenger car tires must meet underthe 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. 6-45