Uniform Tire Quality Grading is a relative comparison system. Tires are graded by manufacturers in three areas: treadwear, traction and temperature.
The treadwear grade is a comparative rating based on the wear of a tire when tested carefully under controlled conditions. For example, a tire graded 400 should have its useful tread last twice as long as a tire graded 200. Treadwear grades are only valid for comparisons within a manufacturer's product line.
Traction grades represent the tire's ability to stop on wet pavement as measured under controlled conditions on asphalt and concrete test surfaces. As of 1997, the traction grades from highest to lowest are "AA","A","B" and "C". The grades do not take into consideration the cornering or turning performance of a tire.
Temperature grades represent a tire's resistance to heat and its ability to dissipate heat when tested under controlled laboratory test conditions. The grades from highest to lowest are "A","B" and "C" . The grade "C" corresponds to the minimum performance required by federal safety standard.