1994 Pontiac Firebird Owner's Manual - Page 220

Uniform Tire Quality Grading The following information relates the to system developed by the United States National Highway Traffic Safety Administration which grades tiresby treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.) Treadwear The treadwear gradeis a comparative rating based on the wear rate the tire of when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would indoor laboratory test wheel. Sustained wear one and a half ( 1 1/2) times as well high temperature can cause the material on the government course as a tire graded of the tire to degenerate and reduce tire 100. The relative performance of tires life, and excessive temperature can lead depends upon the actual conditions of to sudden tire failure. The grade C their use, however, andmay depart corresponds to a level of performance significantly from the norm due to which all passenger car tires must meet variations in driving habits, service under the Federal Motor Vehicle Safety practices and differences in road Standard No. 109. Grades B and A characteristics and climate. represent higher levelsof performance on the laboratory test wheel than the Traction -A, B,C minimum required by law. The traction grades, from highest to Warning: The temperature grade for lowest are: A, B, and C. They represent this tire is established for a tire that is the tire's ability to stop on wet pavement properly inflated and notoverloaded. as measured under controlled conditions Excessive speed, underinflation, or on specified government test surfaces of excessive loading, either separately,,or asphalt and concrete. A tire marked C in combination, can cause heat buildup may have poor traction performance. and possible tire failure. Warning: The traction grade assigned to Those grades are molded on the sidewalls this tire is based on braking of passenger car tires. (straight-ahead) traction tests and does While the tires available as standard or not include cornering (turning) traction. optional equipment on General Motors vehicles may vary with respect to these Temperature -A, B, C grades, all such tires meet General Motors The temperature grades are A (the performance standards and have been highest), B, and C, representing the tire's approved for use on General Motors resistance to the generation of heat and its vehicles. All passengertype (P Metric) 3bility to dissipate heat when tested under tires must conformto Federal safety :ontrolled conditions on a specified requirements in addition to these grades. I 219 ...