1995 Chevrolet Lumina Owner's Manual - Page 237

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 anda half (1 1/2) times as well on government course asa tire the graded 100. The relative performance tires depends of upon the actual conditions their use, however, and of 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 - 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 the United States.) in The traction grades, from highest to lowest are: A, B, and C. They represent the tire's ability to stop wet on pavement as measured under controlled conditions on specified governmenttest surfaces of asphalt and concrete. A tire marked C may have poor traction performance. to Warning: The traction grade assigned this tire is based on braking (straight-ahead) traction tests and does not include cornering (turning) traction. 6-39