Uniform Tire Quality Grading

The following information relates to the tire grading system developed by the National Highway Traffic Safety Administration (NHTSA), which will grade tires by tread wear, traction and temperature performance.

Note: Tires that have deep tread, and winter tires, are exempt from these marking requirements.

Quality grades, where applicable, can be found on the tire sidewall between the tread shoulder and maximum section width. For example:


TREADWEAR 180	TRACTION AA	TEMPERATURE A

In addition to the marking requirements, passenger car tires must conform to Federal Safety Requirements.

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 times as well on a government test course as a tire graded 100. The relative performance of tires depends on 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 both road characteristics and climate.

Traction

Note: The traction grade assigned to this tire is based on straight-ahead braking tests, and does not include acceleration, cornering, hydroplaning, or peak traction characteristics.

The traction grades, from highest to lowest, are: AA, A, B, and C. These grades represent a tire’s ability to stop on a 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.

Temperature

Warning: The temperature grade for this tire is established for a tire that is properly inflated and not overloaded. Excessive speed, under-inflation, or excessive loading, either separately or in combination, can cause heat build-up and possible tire failure.

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.

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 that all passenger car tires must meet under the Federal Motor Safety Standard No. 109.

Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law.