Under UTQG, tires are graded by the manufacturers in three areas; tread wear, traction and temperature resistance.
Tread wearThe tread wear 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 1.5 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, and may depart significantly from the norm due to variations in driving habits, vehicle condition, road characteristics, and climate.
TractionThe traction grades from highest to lowest are AA, A, B and C. They represent a tires ability to stop on 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.
TemperatureThe temperature grades are also A, B and C, representing the tires resistance to heat generation 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; excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger tires must meet under Federal safety laws.