UTQG Ratings:

The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction, and temperature resistance. These tests are conducted independently by each manufacturer following government guidelines to assign values that represent a comparison between the tested tire and a control tire. While traction and temperature resistance are specific performance levels, the treadwear ratings are assigned by the manufacturers following field testing and are most accurate when comparing tires of the same brand.

Treadwear:

Treadwear receives a comparative rating based on wear rate of the tire in field testing following a government specified course. For example, a tire grade of 150 wears 1.5 times longer than a tire graded 100. Actual performance of the tire can vary significantly depending on conditions, driving habits, care, road  characteristics, and climate.

Traction:

Straight-a-head wet braking traction has been represented by a grade of A, B, or C with A being the highest. In 1997 a new top rating of "AA" was introduced to indicate even greater wet braking traction. However, due to its newness, this grade will probably be applied initially to new tire lines as they are introduced and later to existing lines which excel in wet braking, but had been limited to the previous top grade of "A". Traction grades do not indicate wet cornering ability.

Temperature:

Temperature resistance is graded A, B, or C. It represents the tire's resistance to the heat generated by running at high speed. Grade C is the minimum level of performance for all passenger car tires as well as set under Federal Motor Vehicle Safety Standards. This grade is established for a tire that is properly inflated and not overloaded.

Note:  UTQG ratings are not required on winter and light truck sized tires.