Each type of tire is tested under controlled conditions on a government test course and assigned a treadwear grade which theoretically indicates the useful life of the tread. It's important to remember that this is a theoretical figure and cannot be linked to projected tire mileage, as factors like road surface quality, driving habits, inflation, wheel alignment and rotation come into play. Treadwear grades typically range from 60 to 620 in 20 point increments. The higher the grade, the longer the tread life as measured under government conditions. Traction grades indicate a tire's braking performance.
Traction is tested in a straight ahead motion on wet pavement.
Temperature grades represent a tire's ability to withstand heat under test conditions. Since tires are made of rubber and other materials which are degraded by high levels of heat, determining their ability to withstand heat is very important. Temperature grades are also assigned A-C with A signifying the most resistance to heat. For passenger tires, the maximum load and maximum inflation markings indicate the maximum load that can be carried at the maximum pressure. For light truck tires, it is stated in direct relationship to the maximum laod capacity and inflation pressure.