575.104—Uniform tire quality grading standards.

Tire design is the combination of general structural characteristics, materials, and tread pattern, but does include cosmetic, identifying or other minor variations among tires.
(B) Each tire manufactured on and after the effective date of these amendments, other than a tire sold as original equipment on a new vehicle, shall have affixed to its tread surface so as not to be easily removable a label or labels containing its grades and other information in the form illustrated in Figure 2, Parts I and II. The treadwear grade attributed to the tire shall be either imprinted or indelibly stamped on the label containing the material in Part I of Figure 2, directly to the right of or below the word “TREADWEAR.” The traction grade attributed to the tire shall be indelibly circled in an array of the potential grade letters AA, A, B, or C, directly to the right of or below the word “TRACTION” in Part I of Figure 2. The temperature resistance grade attributed to the tire shall be indelibly circled in an array of the potential grade letters A, B, or C, directly to the right of or below the word “TEMPERATURE” in Part I of Figure 2. The words “TREADWEAR,” “TRACTION,” AND “TEMPERATURE,” in that order, may be laid out vertically or horizontally. The text of Part II of Figure 2 may be printed in capital letters. The text of Part I and the text of Part II of Figure 2 need not appear on the same label, but the edges of the two texts must be positioned on the tire tread so as to be separated by a distance of no more than one inch. If the text of Part I and the text of Part II of Figure 2 are placed on separate labels, the notation “See EXPLANATION OF DOT QUALITY GRADES” shall be added to the bottom of the Part I text, and the words “EXPLANATION OF DOT QUALITY GRADES” shall appear at the top of the Part II text. The text of Figure 2 shall be oriented on the tire tread surface with lines of type running perpendicular to the tread circumference. If a label bearing a tire size designation is attached to the tire tread surface and the tire size designation is oriented with lines type running perpendicular to the tread circumference, the text of Figure 2 shall read in the same direction as the tire size designation.
(ii) In the case of the information required by § 575.6(c) to be furnished to prospective purchasers of tires, each tire manufacturer or brand name owner shall, as part of that information, list all possible grades for traction and temperature resistance, and restate verbatim the explanation for each performance area specified in Figure 2. The information need not be in the same format as in Figure 2. The information must indicate clearly and unambiguously the grade in each performance area for each tire of that manufacturer or brand name owner offered for sale at the particular location.
Quality grades can be found where applicable on the tire sidewall between tread shoulder and maximum section width. For example:
(iv) In the case of information required in accordance with § 575.6(a) to be furnished to the first purchaser of a new motor vehicle, each manufacturer of motor vehicles shall, as part of the required information, list all possible grades for traction and temperature resistance and restate verbatim the explanation for each performance area specified in Figure 2 to this section. The information need not be in the format of Figure 2 to this section, but it must contain a statement referring the reader to the tire sidewall for the specific tire grades for the tires with which the vehicle is equipped.
(1) 0.38 or less when tested in accordance with paragraph (f)(2) of this section on the asphalt surface specified in paragraph (f)(1)(i) of this section, or
(2) 0.26 or less when tested in accordance with paragraph (f)(2) of this section on the concrete surface specified in paragraph (f)(1)(i) of this section.
(1) More than 0.38 when tested in accordance with paragraph (f)(2) of this section on the asphalt surface specified in paragraph (f)(1)(i) of this section, and
(2) More than 0.26 when tested in accordance with paragraph (f)(2) of this section on the concrete surface specified in paragraph (f)(1)(i) of this section.
(1) More than 0.47 when tested in accordance with paragraph (f)(2) of this section on the asphalt surface specified in paragraph (f)(1)(i) of this section, and
(2) More than 0.35 when tested in accordance with paragraph (f)(2) of this section on the concrete surface specified in paragraph (f)(1)(i) of this section.
(1) More than 0.54μ when tested in accordance with paragraph (f)(2) of this section on the asphalt surface specified in paragraph (f)(1)(i) of this section; and
(2) More than 0.38μ when tested in accordance with paragraph (f)(2) of this section on the concrete surface specified in paragraph (f)(1)(i) of this section.
(1) Nine-Point Method of Least Squares. For each course monitoring and candidate tire in the convoy, using the average tread depth measurements obtained in accordance with paragraphs (e)(2)(vi) and (e)(2)(viii)(D) of this section and the corresponding mileages as data points, apply the method of least squares as described in appendix C to this section to determine the estimated regression line of y on x given by the following formula:
Where:
y = average tread depth in mils
x = miles after break-in,
a = y intercept of regression line (reference tread depth) in mils, calculated using the method of least squares; and
b = the slope of the regression line in mils of tread depth per 1,000 miles, calculated using the method of least squares. This slope will be negative in value. The tire's wear rate is defined as the absolute value of the slope of the regression line.
(2) Two-Point Arithmetical Method. For each course monitoring and candidate tire in the convoy, using the average tread depth measurements obtained in accordance with paragraph (e)(2)(vi) and (e)(2)(viii)(F) of this section and the corresponding mileages as data points, determine the slope (m) of the tire's wear in mils of tread depth per 1,000 miles by the following formula:
Where:
Yo = average tread depth after break-in, mils
Y1 = average tread depth at 6,400 miles, mils
Xo = 0 miles (after break-in).
X1 = 6,400 miles of travel
This slope (m) will be negative in value. The tire's wear rate is defined as the slope (m) expressed in mils per 1,000 miles.
Note to paragraph (e)(2)(ix)(C): The base wear rate for the course monitoring tires will be obtained by the government by running the tire specified in ASTM E 1136 (incorporated by reference, see § 575.3) course monitoring tires for 6,400 miles 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 the Federal Register. 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 two months after removal from storage.
(1) If the projected mileage is calculated pursuant to paragraph (e)(2)(ix)(A)(1) of this section, then:
Where:
a = y intercept of regression line (reference tread depth) for the candidate tire as determined in accordance with paragraph (e)(2)(ix)(A)(1) of this section.
b1 = the adjusted wear rate for the candidate tire as determined in accordance with paragraph (e)(2)(ix)(D) of this section.
(2) If the projected mileage is calculated pursuant to (e)(2)(ix)(a)(2) of this section, then:

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Where:
Yo = average tread depth after break-in, mils
mc = the adjusted wear rate for the candidate tires as determined in accordance with paragraph (e)(2)(ix)(D) of this section.

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P = Projected mileage × base course wear raten/402
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.
(iv) The test apparatus is a test trailer built in conformity with the specifications in paragraph 4, “Apparatus,” of ASTM E 274 (incorporated by reference, see § 575.3 ). The test apparatus is instrumented in accordance with paragraph 4.5 of that method, except that the “wheel load” in paragraph 4.3 and tire and rim specifications in paragraph 4.4 of that method are as specified in the procedures in paragraph (f)(2) of this section for standard and candidate tires.
(v) The test apparatus is calibrated in accordance with ASTM F 377 (incorporated by reference, see § 575.3 ), with the trailer's tires inflated to 24 psi and loaded to 1,085 pounds.
(B) Mount each tire on a rim of design or measuring rim width specified for tires of its size in accordance with 49 CFR 571.109, S4.4.1 (a) or (b), or a rim having a width within −0 to 0.50 inches of the width listed. Then inflate the tire to 24 psi, or, in the case of a tire with inflation pressure measured in kilopascals, to 180 kPa.
(viii) Prepare two candidate tires of the same construction type, manufacturer, line, and size designation in accordance with paragraph (f)(2)(i) of this section, mount them on the test apparatus, and test one of them according to the procedures of paragraph (f)(2)(ii) through (v) of this section, except load each tire to 85% of the test load specified in § 575.104(h). For CT tires, the test inflation of candidate tires shall be 230 kPa. Candidate tire measurements may be taken either before or after the standard tire measurements used to compute the standard tire traction coefficient. Take all standard tire and candidate tire measurements used in computation of a candidate tire's adjusted traction coefficient within a single three hour period. Average the 10 measurements taken on the asphalt surface to find the candidate tire traction coefficient for the asphalt surface. Average the 10 measurements taken on the concrete surface to find the candidate tire traction coefficient for the concrete surface.

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a) = Measured candidate tire coefficient for asphalt 0.50 −Measured standard tire coefficient for asphalt

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μc=Measured candidate tire coefficient for concrete 0.35 μMeasured standard tire coefficient for concrete
(g) Temperature resistance grading. (1) Mount the tire on a rim of design or measuring rim width specified for tires of its size in accordance with § 571.109, paragraph S4.4.1 (a) or (b) and inflate it to the applicable pressure specified in Table 1 of this section.
Table I—Test Inflation Pressures
[Maximum permissible inflation pressure for the following test]
Test type Tires other than CT tires psi 32 36 40 60 kPa 240 280 300 340 350 CT tires kPa 290 330 350 390
Treadwear test 24 28 32 52 180 220 180 220 180 230 270 230 270
Temperature resistant test 30 34 38 58 220 260 220 260 220 270 310 270 310
Table 2
Maximum inflation pressure Multiplier to be used for treadwear testing Multiplier to be used for traction testing
Tires other than CT tires
32 psi .851 .851
36 psi .870 .797
40 psi .883 .753
240 kPa .866 .866
280 kPa .887 .804
300 kPa .866 .866
340 kPa .887 .804
350 kPa .866 .866
CT tires
290 kPa .866 .866
330 kPa .887 .804
305 kPa .866 .866
390 kPa .887 .804
Table 2A
Tire size designation Temp resistance Max pressure 32 36 40 Traction Treadwear Max pressure 32 36 40
145/70 R13 615 650 685 523 523 553 582
155/70 R13 705 740 780 599 599 629 663
165/70 R13 795 835 880 676 676 710 748
175/70 R13 890 935 980 757 757 795 833
185/70 R13 990 1040 1090 842 842 884 926
195/70 R13 1100 1155 1210 935 935 982 1029
155/70 R14 740 780 815 629 629 663 693
175/70 R14 925 975 1025 786 786 829 871
185/70 R14 1045 1100 1155 888 888 935 982
195/70 R14 1155 1220 1280 982 982 1037 1088
155/70 R15 770 810 850 655 655 689 723
175/70 R15 990 1040 1090 842 842 884 927
185/70 R15 1100 1155 1210 935 935 982 1029
5.60-13 725 810 880 616 616 689 748
5.20-14 695 785 855 591 591 667 727
165-15 915 1,015 1,105 779 779 863 939
185/60 R 13 845 915 980 719 719 778 833

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Figure 2—[Part I]—DOT QUALITY GRADES
TREADWEAR
TRACTIONAAABC
TEMPERATUREABC
(Part II) All Passenger Car Tires Must Conform to Federal Safety Requirements in Addition to These Grades
Treadwear
The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and one-half (11/2) times as well on the government course as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics and climate.
Traction
The traction grades, from highest to lowest, are AA, A, B, and C. Those grades represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. A tire marked C may have poor traction performance. Warning: The traction grade assigned to this tire is based on straight-ahead braking traction tests, and does not include acceleration, cornering, hydroplaning, or peak traction characteristics.
Temperature
The temperature grades are A (the highest), B, and C, representing the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. Warning: The temperature grade for this tire is established for a tire that is properly inflated and not overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.
Appendix A—Treadwear Test Course and Driving Procedures
Introduction. The test course consists of three loops of a total of 400 miles in the geographical vicinity of Goodfellow AFB, San Angelo, Tex.
The first loop runs south 143 miles through the cities of Eldorado, Sonora, and Juno, Tex. to the Camp Hudson Historical Marker, and returns by the same route.
The second loop runs east over Farm and Ranch Roads (FM) and returns to its starting point.
The third loop runs northwest to Water Valley, n