How is a treadwear rating calculated?
The U.S. Department of Transportation (DOT) National Highway Traffic Safety Administration’s (NHTSA) Uniform Tire Quality Grade Standards (UTQG) were designed to help consumers purchase tires using standardized ratings. The treadwear rating relates to the tire’s expected treadwear, traction and temperature capabilities. The rating applies to passenger car tires sold in the United States, but it is not required for deep treaded light truck tires, winter/snow tires, temporary spare tires, trailer tires, tires under 12″ in diameter and other select tires.
The treadwear rating is based on actual testing done on a Course Monitoring Tire (CMT) and the manufacturer’s tire and run on a test track for a 400 mile test loop for a total of 7,200 miles. The tire’s air pressure is checked and the tires rotated every 800 miles during the test. At the conclusion of the test, the tread on both tires are measured and a grade of 100 is assigned to the CMT tire. The manufacturer assigns a grade based on the remaining tread compared to the remaining tread on the CMT tire. A rating of 200 means the manufacturer’s tire is estimated to last twice and long as the CMT tire.
Is the treadwear rating accurate?
Not really. That’s because the rating is based on the tires being run for only 7,200 miles. Tire wear is not always linear. As tread wears down, the tread may wear out faster or slower, depending on the rolling resistance of the tire. So the treadwear rating is an EXTRAPOLATION from the tire manufacturer and is based on their own, sometimes very optimistic, formulas.
Can you compare treadwear ratings between tire manufacturers?
Absolutely not. Each manufacturer is allowed to use their own extrapolation formula to come up with their treadwear rating, so it’s meaningless to compare treadwear ratings between manufacturers. However, you can compare treadwear ratings between a single tire manufacturers different model tires.
©, 2018 Rick MuscoplatPosted on by Rick Muscoplat