Many tires are assigned Uniform Tire Quality Grade (UTQG) ratings that indicate the tire's treadwear resistance, wet traction, and temperature resistance capabilities. The UTQG system was developed by the National Highway Traffic Safety Administration (NHTSA) to help consumers make an informed purchase when buying tires.
While NHTSA regulates UTQG standards and testing methods, the manufacturers are responsible for testing and grading their own tires. Each manufacturer's grading scale may vary slightly, so UTQG ratings are more useful when used to compare tires from the same brand, rather than tires from different manufacturers.
Most passenger car tires are required to undergo UTQG testing and grading to be sold in the United States. Dedicated winter tires, trailer tires, and some light truck tires do not require UTQG ratings. A tire's UTQG ratings can be found on its sidewall. As seen below, the Continental PureContact LS 225/50R17 tire is graded 700 in treadwear, A in traction, and A in temperature. This is commonly given as 700AA for convenience.
The treadwear grade refers to how quickly or slowly a tire wears, based on testing under controlled conditions and using a standardized Course Monitoring tire for comparison. Higher treadwear grades indicate that the tire wears slower and lasts longer, while lower grades indicate that the tire wears out faster and has a shorter lifespan. A 100 treadwear rating indicates that the tire wears at the same rate as the control tire. A 200-graded tire wears twice as slowly as the control tire, while a 300-graded tire wears three times as slowly, and so on.
However, the treadwear grade isn't a measure or guarantee of actual tire mileage. Treadwear is affected by a variety of factors, including driving habits, tire rotation schedule, inflation air pressure, road conditions, and climate, so a tire's tread life may vary depending on the driver.
The traction grade refers to a tire's wet traction capabilities, based on braking tests that assess the tire's ability to stop while sliding on wet asphalt and wet concrete. These tests only assess the tire's straight-line braking on wet surfaces, so a traction grade do not account for cornering, acceleration, hydroplaning, or dry braking. Traction grades are rated as C, B, A, or AA depending on how much traction g-force the tire generates as it slides, with AA-graded tires generating the most wet traction and C-graded tires generating the least. Most tires today have a traction grade of A.
The temperature grade refers to a tire's heat resistance and ability to dissipate heat, based on what speeds the tire can sustain while resisting damage from heat buildup. Temperature grades are given as A for tires that can sustain speeds of 115 mph or greater without heat failure, B for tires that can sustain speeds of at least 100 mph but not 115 mph, and C for tires that can sustain at least 85 mph but not 100 mph. All passenger tires in the United States are required to be capable of sustaining at least 85 mph without heat damage.