1995 Pontiac Grand Am Owner's Manual - Page 250

Treadwear The treadwear grade is a comparative rating based on 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 onthe government course asa tire 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. I It's all right to drive with your compact spar though. It was developed for use on Your vehicl Traction A, B, C T e following information relates to the system h States National Highway developed by the- United Traffic Safety Administration which grades tires by treadwear, tractionm d temperature performance.(This applies-onlyto vehicles sold inthe United States-) The traction grades, from highest to lowest A, B, and are: 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 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