Understanding U.T.Q.G. rates

The Federal Government Uniform Tire Quality Grading Standards apply to passenger car tires only (but excludes deep tread, winter-type snow tires, temporary use spare tires, and tires with nominal rim diameters of twelve inches or less). Tires subject to the standards are required to be graded on the performance factors of treadwear, traction, and temperature. The grades are molded on the tire sidewall, and, in addition for replacement tires, a label affixed to the tread lists and explains these grades. Tire characteristics defined in the Standards are as follows:

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 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 characteristics and climate.

Traction
The traction grades, from highest to lowest, are AA, A, B, and C. Those grades represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. AA being the best, where a tire marked C may have poor traction performance. WARNING: The traction grade assigned o each tire is based on straight-ahead braking traction tests, and does not include acceleration, cornering, hydroplaning, or peak traction characteristics.

Temperature
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 which all passenger car 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 then the minimum required by law. WARNING: The temperature grade for each 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 buildup and possibly tire failure.
 

Examples based on 245/45 r16 Z or W rating, highest available: