1998 Chevrolet Venture Owner's Manual - Page 380

Treadwear The treadwear grade is acomparative rating based on the wear rate of the tire when tested under controlled conditions on a specifiedgovernment 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 relative performance of tires depends upon the actual conditionsof 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. Temperature -- A, B, C The temperature grades are A (the highest),B, and C, representing the tire's resistance to the generationof heat andits ability 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. 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 requiredby law. Warning: The temperature grade for this tire is established for a 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. Traction -- A, B, C The traction grades, from highest to lowest, are A, B, and C, and they represent the tire's ability to stop on wet pavement as measured under controlled conditions on specifiedgovernment test surfacesof 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 anddoes not include cornering (turning) traction. 6-45