Federal Register - August 5, 2021
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Source: Federal Register
Federal Register / Vol. 86, No. 148 / Thursday, August 5, 2021 / Proposed Rules candidate tire in the convoy, using the average tread depth measurements obtained in accordance with paragraphs e2vi and e2viiiF of this section and the corresponding mileages as data points, determine the slope m of the tires wear in mils of tread depth per 1,000 miles by the following formula:
m
= 1000
Yl -Yo Xl _ Xo
Where:
Yo = average tread depth after break-in, mils.
p
=
Y1 = average tread depth after 16 circuits approximately 6,400 miles, mils.
Xo = 0 miles after break-in.
X1 = Total mileage of travel after 16 circuits approximately 6,400 miles.
ii This slope m will be negative in value. The tires wear rate is defined as the slope m expressed in mils per 1,000 miles.
C
Note to paragraph e2ixC: The base wear rate for the course monitoring tires CMTs will be obtained by the Government by running the tire specified in ASTM F2493
incorporated by reference, see 575.3
42775
course monitoring tires for 16 circuits over the San Angelo, Texas, UTQGS test route 4
times per year, then using the average wear rate from the last 4 quarterly CMT tests for the base course wear rate calculation. Each new base course wear rate will be published in Docket No. NHTSA20019395. The course monitoring tires used in a test convoy must be no more than one-year-old at the commencement of the test and must be used within four months after removal from storage.
F Compute the grade P of the of the NHTSA nominal treadwear value for each candidate tire by using the following formula:
Projected mileage x base course wear raten 304
Where base course wear raten = new base course wear rate, i.e., average treadwear of the last 4 quarterly course monitoring tire tests conducted by NHTSA.
Round off the percentage to the nearest lower 20-point increment.
Issued in Washington, DC, under authority delegated in 49 CFR 1.95 and 501.8.
Steven S. Cliff, Acting Administrator.
FR Doc. 202115361 Filed 8421; 8:45 am
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