Treadwear grade

How to read it

The treadwear grade is one of three Uniform Tire Quality Grading Standards grades (49 CFR 575.104), moulded on the sidewall with traction and temperature. The word TREADWEAR is followed by a two- or three-digit number, a percentage of NHTSA’s nominal treadwear value, in multiples of 20. The number comes from a convoy test of about 10,300 km (6,400 miles): 16 circuits of a course of about 640 km (400 miles) near San Angelo, Texas, with the candidate tires’ wear corrected against course monitoring tires run in the same convoy. The regulation’s own explanation says actual wear may depart significantly from the norm with driving habits, service practices, road characteristics and climate.

Also searched as: treadwear rating, UTQG treadwear.

Who assigns the grade

575.104 puts the grading on the tire’s manufacturer or, for tires sold under a brand name, the brand name owner, and says each tire must be able to achieve the performance its grades represent. NHTSA’s tire page describes the grades as a rating by the U.S. Government. Replacement tires also carry a label on the tread that lists and explains the grades, USTMA says.

How grades are spread

NHTSA’s tire page gives the spread across current tires: 15% below 200, 25% from 201 to 300, 32% from 301 to 400, 20% from 401 to 500, 6% from 501 to 600 and 2% above 600.

Tires without a grade

575.104 covers new passenger car tires. It does not apply to deep tread, winter-type snow tires, space-saver or temporary use spare tires, tires for rims of 12 inches or less, or limited production tires. In 1986 NHTSA explained that all-season tires do not count as deep tread, winter-type snow tires, so an M+S all-season tire is still graded.

TREADWEAR or TWI?

The TWI marking at the shoulder is a different thing: it shows where the tread wear bars are, not a grade.