[Code of Federal Regulations]
[Title 49, Volume 6]
[Revised as of October 1, 2006]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR575.104]
[Page 1048-1063]
TITLE 49--TRANSPORTATION
CHAPTER V--NATIONAL HIGHWAY TRAFFIC
SAFETY ADMINISTRATION, DEPARTMENT
OF TRANSPORTATION
PART 575_CONSUMER INFORMATION--Table of Contents
Subpart B_Regulations; Consumer Information Items
Sec. 575.104 Uniform tire quality grading standards.
(a) Scope. This section requires motor vehicle and tire
manufacturers and tire brand name owners to provide information
indicating the relative performance of passenger car tires in the areas
of treadwear, traction, and temperature resistance.
(b) Purpose. The purpose of this section is to aid the consumer in
making an informed choice in the purchase of passenger car tires.
(c) Application. (1) This section applies to new pneumatic tires for
use on passenger cars. However, this section does not apply to deep
tread, winter-type snow tires, space-saver or temporary use spare tires,
tires with nominal rim diameters of 12 inches or less, or to limited
production tires as defined in paragraph (c)(2) of this section.
(2) ``Limited production tire'' means a tire meeting all of the
following criteria, as applicable:
(i) The annual domestic production or importation into the United
States by the tire's manufacturer of tires of the same design and size
as the tire does not exceed 15,000 tires;
(ii) In the case of a tire marketed under a brand name, the annual
domestic purchase or importation into the United States by a brand name
owner of tires of the same design and size as the tire does not exceed
15,000 tires;
(iii) The tire's size was not listed as a vehicle manufacturer's
recommended tire size designation for a new motor vehicle produced in or
imported into the United States in quantities greater than 10,000 during
the calendar year preceeding the year of the tire's manufacture; and
(iv) The total annual domestic production or importation into the
United States by the tire's manufacturer, and in the case of a tire
marketed under a brand name, the total annual domestic purchase or
purchase for importation into the United States by the tire's brand name
owner, of tires meeting the criteria of paragraphs (c)(2) (i), (ii), and
(iii) of this section, does not exceed 35,000 tires.
Tire design is the combination of general structural characteristics,
materials, and tread pattern, but does include cosmetic, identifying or
other minor variations among tires.
(d) Requirements--(1) Information. (i) Each manufacturer of tires,
or in the case of tires marketed under a brand name, each brand name
owner, shall provide grading information for each tire of which he is
the manufacturer or brand name owner in the manner set forth in
paragraphs (d)(1)(i) (A) and (B) of this section. The grades for each
tire shall be only those specified in paragraph (d)(2) of this section.
Each tire shall be able to achieve the level of performance represented
by each grade with which it is labeled. An individual tire need not,
however, meet further requirements after having been subjected to the
test for any one grade.
(A) Except for a tire of a new tire line, manufactured within the
first six months of production of the tire line, each tire shall be
graded with the words, letters, symbols, and figures specified in
paragraph (d)(2) of this section, permanently molded into or onto the
tire sidewall between the tire's maximum section width and shoulder in
accordance with one of the methods described in Figure 1. For purposes
of this paragraph, new tire line shall mean a group of tires differing
substantially in construction, materials, or design from those
previously sold by the manufacturer or brand name owner of the tires. As
used in this paragraph, the term ``construction'' refers to the internal
structure of the tire (e.g., cord angles, number and placement of
breakers), ``materials'' refers to the substances used in manufacture of
the tire (e.g., belt fiber, rubber compound), and ``design'' refers to
properties or conditions imposed by the tire mold (e.g., aspect ratio,
tread pattern).
(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.''
[[Page 1049]]
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 Sec. 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.
(iii) Each manufacturer of motor vehicles equipped with passenger
car tires shall include in the owner's manual of each such vehicle a
list of all possible grades for traction and temperature resistance and
restate verbatim the explanation for each performance area specified in
Figure 2, Part II. The information need not be in the exact format of
Figure 2, Part II, 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, as follows:
Uniform Tire Quality Grading
Quality grades can be found where applicable on the tire sidewall
between tread shoulder and maximum section width. For example:
Treadwear 200 Traction AA Temperature A
(iv) In the case of information required in accordance with Sec.
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.
(2) Performance--(i) Treadwear. Each tire shall be graded for
treadwear performance with the word ``TREADWEAR'' followed by a number
of two or three digits representing the tire's grade for treadwear,
expressed as a percentage of the NHTSA nominal treadwear value, when
tested in accordance with the conditions and procedures specified in
paragraph (e) of this section. Treadwear grades shall be expressed in
multiples of 20 (for example, 80, 120, 160).
(ii) Traction. Each tire shall be graded for traction performance
with the word ``TRACTION,'' followed by the symbols AA, A, B, or C, when
the tire is tested in accordance with the conditions and
[[Page 1050]]
procedures specified in paragraph (f) of this section.
(A) The tire shall be graded C when the adjusted traction
coefficient is either:
(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.
(B) The tire may be graded B only when its adjusted traction
coefficient is both:
(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.
(C) The tire may be graded A only when its adjusted traction
coefficient is both:
(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.
(D) The tire may be graded AA only when its adjusted traction
coefficient is both:
(1) More than 0.54[mu] 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 0.38[mu] when tested in accordance with paragraph
(f)(2) of this section on the concrete surface specified in paragraph
(f)(1)(i) of this section.
(iii) Temperature resistance. Each tire shall be graded for
temperature resistance performance with the word ``TEMPERATURE''
followed by the letter A, B, or C, based on its performance when the
tire is tested in accordance with the procedures specified in paragraph
(g) of this section. A tire shall be considered to have successfully
completed a test stage in accordance with this paragraph if, at the end
of the test stage, it exhibits no visual evidence of tread, sidewall,
ply, cord, innerliner, or bead separation, chunking, broken cords,
cracking or open splices as defined in Sec. 571.109 of this chapter,
and the tire pressure is not less than the pressure specified in
paragraph (g)(1) of this section.
(A) The tire shall be graded C if it fails to complete the 500 rpm
test stage specified in paragraph (g)(9) of this section.
(B) The tire may be graded B only if it successfully completes the
500 rpm test stage specified in paragraph (g)(9) of this section.
(C) The tire may be graded A only if it successfully completes the
575 rpm test stage specified in paragraph (g)(9) of this section.
(e) Treadwear grading conditions and procedures--(1) Conditions. (i)
Tire treadwear performance is evaluated on a specific roadway course
approximately 400 miles in length, which is established by the NHTSA
both for its own compliance testing and for that of regulated persons.
The course is designed to produce treadwear rates that are generally
representative of those encountered by tires in public use. The course
and driving procedures are described in appendix A of this section.
(ii) Treadwear grades are evaluated by first measuring the
performance of a candidate tire on the government test course, and then
correcting the projected mileages obtained to account for environmental
variations on the basis of the performance of the course monitoring
tires run in the same convoy.
(iii) In convoy tests, each vehicle in the same convoy, except for
the lead vehicle, is throughout the test within human eye range of the
vehicle immediately ahead of it.
(iv) A test convoy consists of two or four passenger cars, light
trucks, or MPVs, each with a GVWR of 10,000 pounds or less.
(v) On each convoy vehicle, all tires are mounted on identical rims
of design or measuring rim width specified for tires of that size in
accordance with
[[Page 1051]]
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.
(2) Treadwear grading procedure. (i) Equip a convoy as follows:
Place four course monitoring tires on one vehicle. Place four candidate
tires with identical size designations on each other vehicle in the
convoy. On each axle, place tires that are identical with respect to
manufacturer and line.
(ii) Inflate each candidate and each course monitoring tire to the
applicable pressure specified in Table 1 of this section.
(iii) Load each vehicle so that the load on each course monitoring
and candidate tire is 85 percent of the test load specified in Sec.
575.104(h).
(iv) Adjust wheel alignment to the midpoint of the vehicle
manufacturer's specifications, unless adjustment to the midpoint is not
recommended by the manufacturer; in that case, adjust the alignment to
the manufacturer's recommended setting. In all cases, the setting is
within the tolerance specified by the manufacturer of the alignment
machine.
(v) Subject candidate and course monitoring tires to ``break-in'' by
running the tires in the convoy for two circuits of the test roadway
(800 miles). At the end of the first circuit, rotate each vehicle's
tires by moving each front tire to the same side of the rear axle and
each rear tire to the opposite side of the front axle. Visually inspect
each tire for any indication of abnormal wear, tread separation, bulging
of the sidewall, or any sign of tire failure. Void the grading results
from any tire with any of these anomalies, and replace the tire.
(vi) After break-in, allow the air pressure in the tires to fall to
the applicable pressure specified in Table 1 of this section or for 2
hours, whichever occurs first. Measure, to the nearest 0.001 inch, the
tread depth of each candidate and each course monitoring tire, avoiding
treadwear indicators, at six equally spaced points in each groove. For
each tire compute the average of the measurements. Do not measure those
shoulder grooves which are not provided with treadwear indicators.
(vii) Adjust wheel alignment to the midpoint of the manufacturer's
specifications, unless adjustment to the midpoint is not recommended by
the manufacturer; in that case, adjust the alignment according to the
manufacturer's recommended setting. In all cases, the setting is within
the tolerance specified by the manufacturer of the alignment machine.
(viii) Drive the convoy on the test roadway for 6,400 miles.
(A) After each 400 miles, rotate each vehicle's tires by moving each
front tire to the same side of the rear axle and each rear tire to the
opposite side of the front axle. Visually inspect each tire for
treadwear anomalies.
(B) After each 800 miles, rotate the vehicles in the convoy by
moving the last vehicle to the lead position. Do not rotate driver
positions within the convoy. In four-car convoys, vehicle one shall
become vehicle two, vehicle two shall become vehicle three, vehicle
three shall become vehicle four, and vehicle four shall become vehicle
one.
(C) After each 800 miles, if necessary, adjust wheel alignment to
the midpoint of the vehicle manufacturer's specification, unless
adjustment to the midpoint is not recommended by the manufacturer; in
that case, adjust the alignment to the manufacturer's recommended
setting. In all cases, the setting is within the tolerance specified by
the manufacturer of the alignment machine.
(D) After each 800 miles, if determining the projected mileage by
the 9-point method set forth in (e)(2)(ix)(A)(1), measure the average
tread depth of each tire following the procedure set forth in paragraph
(e)(2)(vi) of this section.
(E) After each 1,600 miles, move the complete set of four tires to
the following vehicle. Move the tires on the last vehicle to the lead
vehicle. In moving the tires, rotate them as set forth in
(e)(2)(viii)(A) of this section.
(F) At the end of the test, measure the tread depth of each tire
pursuant to the procedure set forth in paragraph (e)(2)(vi) of this
section.
(ix)(A) Determine the projected mileage for each candidate tire
either by the nine-point method of least squares set forth in paragraph
(e)(2)(ix)(A)(1) of this section and appendix C to this section, or by
the two-point arithmetical
[[Page 1052]]
method set forth in paragraph (e)(2)(ix)(A)(2) of this section. Notify
NHTSA about which of the alternative grading methods is being used.
(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:
[GRAPHIC] [TIFF OMITTED] TC01AU91.184
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:
[GRAPHIC] [TIFF OMITTED] TC01AU91.185
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.
(B) Average the wear rates of the four course monitoring tires as
determined in accordance with paragraph (e)(2)(ix)(A) of this section.
(C) Determine the course severity adjustment factor by dividing the
base course wear rate for the course monitoring tires (see Note to this
paragraph) by the average wear rate for the four course monitoring
tires.
Note to paragraph (e)(2)(ix)(C): The base wear rate for the course
monitoring tires will be obtained by the government by running ASTM E-
1136 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 filed in the DOT
Docket Management section. This value will be furnished to the tester by
the government at the time of the test. 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.
(D) Determine the adjusted wear rate for each candidate tire by
multiplying its wear rate determined in accordance with paragraph
(e)(2)(ix)(A) of this section by the course severity adjustment factor
determined in accordance with paragraph (e)(2)(ix)(C) of this section.
(E) Determine the projected mileage for each candidate tire by
applying the appropriate formula set forth below:
(1) If the projected mileage is calculated pursuant to paragraph
(e)(2)(ix)(A)(1) of this section, then:
[GRAPHIC] [TIFF OMITTED] TC01AU91.186
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.
b\1\ = 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:
[GRAPHIC] [TIFF OMITTED] TR07SE99.000
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.
(F) Compute the grade (P) of the NHTSA nominal treadwear value for
[[Page 1053]]
each candidate tire by using the following formula:
P = Projected mileage x 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.
(f) Traction grading conditions and procedures--(1) Conditions. (i)
Tire traction performance is evaluated on skid pads that are
established, and whose severity is monitored, by the NHTSA both for its
compliance testing and for that of regulated persons. The test pavements
are asphalt and concrete surfaces constructed in accordance with the
specifications for pads ``C'' and ``A'' in the ``Manual for the
Construction and Maintenance of Skid Surfaces,'' National Technical
Information Service No. DOT-HS-800-814. The surfaces have locked wheel
traction coefficients when evaluated in accordance with paragraphs
(f)(2)(i) through (f)(2)(vii) of this section of 0.50 0.10 for the asphalt and 0.35 0.10
for the concrete. The location of the skid pads is described in appendix
B to this section.
(ii) The standard tire is the American Society for Testing and
Materials (ASTM) E 501 ``Standard Tire for Pavement Skid Resistance
Tests.''
(iii) The pavement surface is wetted in accordance with paragraph
3.5, ``Pavement Wetting System,'' of ASTM Method E 274-79, ``Skid
Resistance of Paved Surfaces Using a Full-Scale Tire.''
(iv) The test apparatus is a test trailer built in conformity with
the specifications in paragraph 3, ``Apparatus,'' of ASTM Method E 274-
79, and instrumented in accordance with paragraph 3.3.2 of that method,
except that ``wheel load'' in paragraph 3.2.2 and tire and rim
specifications in paragraph 3.2.3 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 Method
F 377-74, ``Standard Method for Calibration of Braking Force for Testing
of Pneumatic Tires'' with the trailer's tires inflated to 24 psi and
loaded to 1,085 pounds.
(vi) Consecutive tests on the same surface are conducted not less
than 30 seconds apart.
(vii) A standard tire is discarded in accordance with ASTM Method E
501.
(2) Procedure. (i) Prepare two standard tires as follows:
(A) Condition the tires by running them for 200 miles on a pavement
surface.
(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.
(C) Statically balance each tire-rim combination.
(D) Allow each tire to cool to ambient temperature and readjust its
inflation pressure to 24 psi, or, in the case of a tire with inflation
pressure measured in kilopascals, to 180 kPa.
(ii) Mount the tires on the test apparatus described in paragraph
(f)(1)(iv) of this section and load each tire to 1,085 pounds.
(iii) Tow the trailer on the asphalt test surface specified in
paragraph (f)(1)(i) of this section at a speed of 40 mph, lock one
trailer wheel, and record the locked-wheel traction coefficient on the
tire associated with that wheel between 0.5 and 1.5 seconds after
lockup.
(iv) Repeat the test on the concrete surface, locking the same
wheel.
(v) Repeat the tests specified in paragraphs (f)(2) (iii) and (iv)
of this section for a total of 10 measurements on each test surface.
(vi) Repeat the procedures specified in paragraphs (f)(2) (iii)
through (v) of this section, locking the wheel associated with the other
tire.
(vii) Average the 20 measurements taken on the asphalt surface to
find the standard tire traction coefficient for the asphalt surface.
Average the 20 measurements taken on the concrete
[[Page 1054]]
surface to find the standard tire traction coefficient for the concrete
surface. The standard tire traction coefficient so determined may be
used in the computation of adjusted traction coefficients for more than
one candidate tire.
(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 Sec. 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.
(ix) Compute a candidate tire's adjusted traction coefficient for
asphalt ([mu]a) by the following formula:
([mu]a) = Measured candidate tire coefficient for
asphalt+0.50 -Measured standard tire coefficient for asphalt
(x) Compute a candidate tire's adjusted traction coefficient for
concrete ([mu]c) by the following formula:
[mu]c=Measured candidate tire coefficient for concrete +0.35
[mu]Measured 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 Sec. 571.109, paragraph S4.4.1 (a) or (b) and inflate
it to the applicable pressure specified in Table 1 of this section.
(2) Condition the tire-rim assembly to a temperature of 95 [deg]F
for at least 3 hours.
(3) Adjust the pressure again to the applicable pressure specified
in Table 1 of this section.
(4) Mount the tire-rim assembly on an axle, and press the tire tread
against the surface of a flat-faced steel test wheel that is 67.23
inches in diameter and at least as wide as the section width of the
tire.
(5) During the test, including the pressure measurements specified
in paragraphs (g) (1) and (3) of this section, maintain the temperature
of the ambient air, as measured 12 inches from the edge of the rim
flange at any point on the circumference on either side of the tire at
95 [deg]F. Locate the temperature sensor so that its readings are not
affected by heat radiation, drafts, variations in the temperature of the
surrounding air, or guards or other devices.
(6) Press the tire against the test wheel with a load of 88 percent
of the tire's maximum load rating as marked on the tire sidewall.
(7) Rotate the test wheel at 250 rpm for 2 hours.
(8) Remove the load, allow the tire to cool to 95 [deg]F or for 2
hours, whichever occurs last, and readjust the inflation pressure to the
applicable pressure specified in Table 1 of this section.
(9) Reapply the load and without interruption or readjustment of
inflation pressure, rotate the test wheel at 375 rpm for 30 minutes, and
then at successively higher rates in 25 rpm increments, each for 30
minutes, until the tire has run at 575 rpm for 30 minutes, or to
failure, whichever occurs first.
Table I--Test Inflation Pressures
[Maximum permissible inflation pressure for the following test]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tires other than CT tires CT tires
------------------------------------------------------------------------------------------
Test type psi kPa kPa
------------------------------------------------------------------------------------------
32 36 40 60 240 280 300 340 350 290 330 350 390
--------------------------------------------------------------------------------------------------------------------------------------------------------
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
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 1055]]
(h) Determination of test load. (1) To determine test loads for
purposes of paragraphs (e)(2)(iii) and (f)(2)(viii), follow the
procedure set forth in paragraphs (h) (2) through (5) of this section.
(2) Determine the tire's maximum inflation pressure and maximum load
rating both as specified on the tire's sidewall.
(3) Determine the appropriate multiplier corresponding to the tire's
maximum inflation pressure, as set forth in Table 2.
(4) Multiply the tire's maximum load rating by the multiplier
determined in paragraph (h)(3). This is the tire's calculated load.
(5) Round the product determined in paragraph (h)(4) (the calculated
load) to the nearest multiple of ten pounds or, if metric units are
used, 5 kilograms. For example, 903 pounds would be rounded to 900 and
533 kilograms would be rounded to 535. This figure is the test load.
Table 2
------------------------------------------------------------------------
Multiplier Multiplier
to be used to be used
Maximum inflation pressure for for
treadwear traction
testing 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
----------------------------------------------------------------------------------------------------------------
Temp resistance Treadwear
--------------------------- --------------------------
Tire size designation Max pressure Traction Max pressure
--------------------------- --------------------------
32 36 40 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
----------------------------------------------------------------------------------------------------------------
(i)-(l) [Reserved]
[[Page 1056]]
[GRAPHIC] [TIFF OMITTED] TC01AU91.196
Figure 2--[Part I]--DOT QUALITY GRADES
TREADWEAR
TRACTION AA A B C
TEMPERATURE A B C
[[Page 1057]]
(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 (1\1/2\) 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, northeast toward
Robert Lee and returns via Texas 208 to the vicinity of Goodfellow AFB.
Route. The route is shown in Figure 3. The table identifies key
points by number. These numbers are encircled in Figure 3 and in
parentheses in the descriptive material that follows.
Southern Loop. The course begins at the intersection (1) of Ft.
McKavitt Road and Paint Rock Road (FM388) at the northwest corner of
Goodfellow AFB. Drive east via FM 388 to junction with Loop Road 306
(2). Turn right onto Loop Road 306 and proceed south to junction with
US277 (3). Turn onto US277 and proceed south through Eldorado and Sonora
(4), continuing on US277 to junction with FM189 (5). Turn right onto
FM189 and proceed to junction with Texas 163 (6). Turn left onto Texas
163, and at the option of the manufacturer:
(A) Proceed south to Camp Hudson Historical Marker and onto the
paved shoulder (7). Reverse route to junction of Loop Road 306 and FM
388 (2); or
(B) Proceed south to junction with Frank's Crossing. Reverse route
at Frank's Crossing and proceed north on Texas 163 to junction with
Highway 189; Reverse route at junction with Highway 189; proceed south
on Texas 163 to junction with Frank's Crossing; reverse route at Frank's
Crossing and proceed north to junction of Loop Road 306 and FM 388 (2).
Eastern Loop. From junction of Loop Road 306 and FM388 (2), make
right turn onto FM388 and drive east to junction with FM2334 (13). Turn
right onto FM2334 and proceed south across FM765 (14) to junction of
FM2334 and US87 (15). For convoys that originate at Goodfellow AFB, make
U-turn and return to junction of FM388 and Loop Road 306 (2) by the same
route. For convoys that do not originate at Goodfellow AFB, upon
reaching junction of FM2334 and US87 (15), make U-Turn and continue
north on FM2334 past the intersection with FM388 to Veribest Cotton Gin,
a distance of 1.8 miles beyond the intersection. Make U-turn and return
to junction of FM2334 and FM388. Turn right onto FM388, proceed west to
junction FM388 and Loop Road 306.
Northwestern Loop. From junction of Loop Road 306 and FM388 (2),
make right turn onto Loop Road 306. Proceed onto US277, to junction with
FM2105 (8). Turn left onto FM2105 and proceed west to junction with US87
(10). Turn right on US87 and proceed northwest to the junction with
FM2034 near the town of Water Valley (11). Turn right onto FM2034 and
proceed north to Texas 208 (12). Turn right onto Texas 208 and proceed
south to junction with FM2105 (9). Turn left onto FM2105 and proceed
east to junction with
[[Page 1058]]
US277 (8). Turn right onto US277 and proceed south onto Loop Road 306 to
junction with FM388 (2). For convoys that originate at Goodfellow AFB,
turn right onto FM388 and proceed to starting point at junction of Ft.
McKavitt Road and FM388 (1). For convoys that do not originate at
Goodfellow AFB, do not turn right onto FM388 but continue south on Loop
Road 306.
Driving instructions. The drivers shall run at posted speed limits
throughout the course unless an unsafe condition arises. If such
condition arises, the speed should be reduced to the maximum safe
operating speed.
Braking Procedures at STOP signs. There are a number of
intersections at which stops are required. At each of these
intersections a series of signs is placed in a fixed order at follows:
Sign Legend
Highway Intersection 1000 (or 2000) Feet
STOP AHEAD
Junction XXX
Direction Sign (Mereta[rarr])
STOP or YIELD
Procedures. 1. Approach each intersection at posted speed limit.
2. When abreast of the STOP AHEAD sign, apply the brakes so that the
vehicle decelerates smoothly to 20 mph when abreast of the direction
sign.
3. Come to a complete stop at the STOP sign or behind any vehicle
already stopped.
[[Page 1059]]
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[[Page 1060]]
[GRAPHIC] [TIFF OMITTED] TC01AU91.191
Appendix B--Traction Skid Pads
Two skid pads have been laid on an unused runway and taxi strip on
Goodfellow AFB. Their location is shown in Figure 4.
The asphalt skid pad is 600 ft.x60 ft. and is shown in black on the
runway in Figure 4. The pad is approached from either end by a
[[Page 1061]]
75 ft. ramp followed by 100 ft. of level pavement. This arrangement
permits the skid trailers to stabilize before reaching the test area.
The approaches are shown on the figure by the hash-marked area.
The concrete pad is 600 ft.x48 ft. and is on the taxi strip. The
approaches to the concrete pad are of the same design as those for the
asphalt pads.
A two lane asphalt road has been built to connect the runway and
taxi strip. The road is parallel to the northeast-southwest runway at a
distance of 100 ft. The curves have super-elevation to permit safe exit
from the runway at operating speeds.
[GRAPHIC] [TIFF OMITTED] TC01AU91.192
Appendix C--Method of Least Squares
The method of least squares is a method of calculation by which it
is possible to obtain a reliable estimate of a true physical
relationship from a set of data which involve random error. The method
may be used to establish a regression line that minimizes the sum of the
squares of the deviations of the measured data points from the line. The
regression line is consequently described as the line of ``best fit'' to
the data points. It is described in terms of its slope and its ``y''
intercept.
The graph in Figure 5 depicts a regression line calculated using the
least squares method from data collected from a hypothetical treadwear
test of 6,400 miles, with tread depth measurements made at every 500
miles.
[[Page 1062]]
[GRAPHIC] [TIFF OMITTED] TC01AU91.193
In this graph, xj,yj (j=0, 1, . . ;. 8) are
the individual data points representing the tread depth measurements
(the overall average for the tire with 6 measurements in each tire
groove) at the beginning of the test (after break-in) and at the end of
each 800-mile segment of the test.
The absolute value of the slope of the regression line is an
expression of the mils of tread worn per 1,000 miles, and is calculated
by the following formula:
[GRAPHIC] [TIFF OMITTED] TC01AU91.194
The ``y'' intercept of the regression line (a) in mils is calculated
by the following formula:
[GRAPHIC] [TIFF OMITTED] TC01AU91.195
Appendix D--User Fees
1. Course Monitoring Tires: A fee of $333.00 will be assessed for
each course monitoring tire purchased from NHTSA at Goodfellow Air Force
Base, San Angelo, Texas. This fee is based upon the direct and indirect
costs attributable to: (a) the purchase of course monitoring tires by
NHTSA, (b) a pro rata allocation of salaries and general facility costs
associated with maintenance of the tires, and (c) warehouse storage fees
for the tires.
2. Use of Government Traction Skid Pads: A fee of $34.00 will be
assessed for each hour, or fraction thereof, that the traction skid pads
at Goodfellow Air Force Base, San Angelo, Texas are used. This fee is
based upon the direct and indirect costs attributable to: (a)
depreciation on facilities and equipment comprising or used in
conjunction with the traction skid pads (i.e., skid system, water truck,
air compressor, skid track, tractor sweeper, equipment, buildings), (b)
the calibration of the traction skid pads, and (c) a pro rata allocation
of salaries and general facility costs associated with maintenance of
the traction skid pads.
3. Fee payments shall be by check, draft, money order, or Electronic
Funds Transfer
[[Page 1063]]
System made payable to the Treasurer of the United States.
4. The fees set forth in this appendix continue in effect until
adjusted by the Administrator of NHTSA. The Administrator reviews the
fees set forth in this appendix and, if appropriate, adjusts them by
rule at least every 2 years.
[43 FR 30549, July 17, 1978]
Editorial Note: For Federal Register citations affecting Sec.
575.104, see the List of CFR Sections Affected, which appears in the
Finding Aids section of the printed volume and on GPO Access.