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.