The Department of Transportation (DOT) and National Highway Traffic Safety Administration (NHTSA) developed the Uniform Tire Quality Grading (UTQG) standard to provide consumers with information to make an informed decision during tire purchase. All tires sold from 1979 are required to have a UTQG marking on the sidewall. UTQG markings are not required for deep-treaded light truck tires, winter/snow tires, temporary spare tires, trailer tires, and tires under 12-inches in diameter. Some other exceptions may exist. The UTQG marking consists of treadwear, traction and temperature.
Treadwear
The treadwear marking demonstrates how long a tire can last. Treadwear has a range between 100-1000, where, for example, an 800 UTQG tire will last twice as long as a 400 UTQG tire. Tire treadwear performance is evaluated on a specific roadway course approximately 400 miles in length, which is established by the NHTSA. The course is designed to produce treadwear rates that are generally representative of those encountered by tires on public roads.
Traction
Traction markings indicate how well a tire will perform in wet conditions. The traction rating can be AA, A, B or C. AA is the highest level of wet traction and C is the lowest. The table below shows the wet traction coefficient on two different surfaces.
Tire traction performance is evaluated on skid pads that are established, and whose severity is monitored by the NHTSA. The test pavements are asphalt and concrete surfaces, constructed in accordance with the specifications for pads. The skid trailer is pulled behind a truck at a speed of 40 mph over test surfaces. The tire's coefficient of friction will be measured when the tire slides.
Temperature
Temperature resistance indicates how a tire mainly performs in high-speed situations. The temperature ratings are A, B and C. Tires with a rating of A will be able to perform at speeds above 115 mph, while tires with a B rating are able to perform at speeds between 100-115 mph. Grade C tires can perform between 85-100 mph. Temperature resistance grading is performed in a laboratory when an inflated tire is tested against a high-speed drum.
