Tires are graded by tire manufacturers in controlled tests that meet the U.S. Department of Transportation (DOT) and National Highway Traffic Safety Administration (NHTSA) specific standards of performance including: tread wear, traction and temperature tolerance. These “grades” are molded on the tire sidewall. You can also find the UTOG ratings printed on the delivery stickers attached to your new tires.
The tread wear grade is a comparative rating based on the wear rate of the tire evaluated under government-controlled conditions on a test course.
For example, a tire graded 240 would wear twice as fast as a tire with a 480 tread wear rating. Actual tire performance depends on “real’’ conditions and may depart significantly from the standardized test environment. The tread wear rating can be used as a guide, but should not be viewed as an absolute. Manufacturers tread warranties can be viewed as a similar guide.
The traction grade – AA, A, B and C – represents a tire's ability to stop on wet pavement as measured under controlled conditions on test surfaces of asphalt and concrete. For comparison a tire with a traction grade of AA has better traction performance than a tire graded C.
Note: The traction grade assigned to each tire is based on straight-ahead braking tests. It does not include acceleration, cornering, resistance to hydroplaning or other peak traction characteristics.
The temperature grades (A – the highest, B and C) represent the tire's resistance to heat when tested under controlled conditions on laboratory test-wheel. Sustained high temperature can create deterioration and reduced tread life. Excessive temperature can lead to sudden tire failure.
All passenger tires must meet the minimum heat resistance standard of a C – Federal Motor Vehicle Safety Standard No. 109. Grades A and B represent higher levels of performance than what the law requires.
Note: Even a superior temperature grade will not prevent damage to or failure of a tire improperly inflated, overloaded or exposed to excessive speed.