How to: Read tire quality ratings

[MMamdouh]

NHTSA rates the quality of tires based on three criteria: temperature, traction and treadwear.

TEMPERATURE

Letter grades are used to rank tires for heat resistance, graded "A" (highest); "B," or "C" (lowest).

A "C" grade represents the minimum performance standard required by Federal regulation.

Currently, 27 percent of tires are rated "A;" 59 percent are rated "B;" and 14 percent are rated "C."

A tire?s ability to resist heat is an important safety factor. Tires driven long distances in hot weather can deteriorate, leading to rare instances of tread separation and blowouts.

TRACTION

Also rated with letter grades. A tire that carries a higher grade should allow a car to stop on a wet road in a shorter distance than a tire with a lower grade.

Traction is graded "AA" (highest); "A;" "B," or "C" (lowest). A "C" grade can indicate poor performance. Currently, 3 percent of tires are rated "AA;" 75 percent are "A;" and 22 percent are "B." There is only one "C" rated line of tires.

TREADWEAR

A control tire is assigned a grade of 100. A tire with a grade of 200 can be expected to last twice as long as the control tire, while a tire with a grade of 80 is normally less durable.

Currently, the highest reported treadwear
rating is 700; 98 percent of tires rank 600 or below; 92 percent rank 500 or
below; 72 percent rank 400 or below; 40 percent rank 300 or below; and 5
percent rank 200 or below.

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Tread Wear: This number comes from testing the tire in controlled conditions on a government test track. The higher the number, the longer you can expect the tread to last.

Since no one will drive his or her car on exactly the same surfaces and at the same speeds as the government test track, the number is not an accurate indicator of how long your tread will actually last. It's a good relative measure, however: You can expect a tire with a larger number to last longer than one with a smaller number.

Traction: Tire traction is rated AA, A, B or C, with AA at the top of the scale. This rating is based on the tire's ability to stop a car on wet concrete and asphalt.

It does not indicate the tire's cornering ability. According to this NHTSA page, the Firestone Wilderness AT and Radial ATX II tires that have been in the news have a traction rating of B.

Temperature: The tire temperature ratings are A, B or C. The rating is a measure of how well the tire dissipates heat and how well it handles the buildup of heat. The temperature grade applies to a properly inflated tire that is not overloaded.

Underinflation, overloading or excessive speed can lead to more heat buildup.Excessive heat buildup can cause tires to wear out faster, or could even lead to tire failure. According to this NHTSA page, the Firestone Wilderness AT and Radial ATX II tires have a temperature rating of C.

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