DEPARTMENT OF TRANSPORTATION UNIFORM TIRE QUALITY GRADES
The following tire grading categories were established by the National Highway Traffic Safety Administration. The specific grade rating assigned by the tire’s manu- facturer in each category is shown on the sidewall of the tires on your vehicle.
All passenger vehicle tires must conform to Federal safety requirements in addition to these grades.
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 one-half times as well on the government course as a 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 charac- teristics and climate.
The Traction grades, from highest to lowest, are AA, A, B, and C. These grades represent the tire’s ability to stop on wet pavement, as measured under controlled condi- tions on specified government test surfaces of asphalt and concrete. A tire marked C may have poor traction performance.
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 pas- senger vehicle 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 required by law.
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Temperature Grades
The Temperature grades are A (the highest), B, and C, representing the tire’s resistance to the generation of heat and its ability to dissipate heat, when tested under controlled conditions on a specified indoor laboratory test wheel.
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