Consumer Information Regulations: Uniform Tire Quality Grading Test Procedures

This final rule amends the treadwear testing procedures under the Uniform Tire Quality Grading Standards (UTQGS). To ensure the consistency of the treadwear grades from one year to the next, the agency monitors the changing roughness of the test course, periodically calculates a base course wear rate (BCWR), and uses it to adjust the measured wear rates of tires driven over the course. To monitor the test course, the agency uses special tires designated as course monitoring tires (CMTs). The agency is amending the UTQGS to change the computation of the BCWR used in calculating the treadwear grade of passenger car tires. These amendments establish a direct comparison of the wear rates of CMTs used as the control standard with the wear rates of the candidate tires, i.e., the tires being tested for the purposes of grading. This direct comparison will result in more consistent treadwear ratings by compensating for any changes or variations in CMT characteristics. NHTSA will measure the wear rate of CMTs 4 times per year and use the average wear rate from the last 4 quarterly CMT tests as a basis for the BCWR. NHTSA is further requiring that CMTs used to determine wear rate be not more than 1 year old at the commencement of the test and that the CMTs used in the test must be used within 2 months after removal from storage.