[Federal Register Volume 65, Number 101 (Wednesday, May 24, 2000)]
[Rules and Regulations]
[Pages 33481-33486]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-12873]



National Highway Traffic Safety Administration

49 CFR Part 575

[Docket No. 00-7364]
RIN 2127-AG96

Consumer Information Regulations: Uniform Tire Quality Grading 
Test Procedures

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation (DOT).

ACTION: Final rule.


SUMMARY: 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.

DATES: Effective date: The amendments in this final rule are effective 
July 24, 2000.
    Petitions for reconsideration of this final rule must be received 
by NHTSA not later than July 10, 2000.

ADDRESSES: Petitions for reconsideration should be submitted to the 
Administrator, National Highway Traffic Safety Administration, 400 
Seventh Street, SW, Washington, DC 20590.

    For technical issues: Mr. Sanjay Patel, Safety Standards Engineer, 
Office of Planning and Consumer Programs, Office of Safety Performance 
Standards, National Highway Traffic Safety Administration, 400 Seventh 
Street, SW, Washington, DC 20590; telephone (202) 366-0307.
    For legal issues: Mr. Stephen P. Wood, Assistant Chief Counsel for 
Rulemaking, National Highway Traffic Safety Administration, 400 Seventh 
Street, SW, Washington, DC 20590; telephone (202) 366-2992.


A. Background

1. Current Provisions.

    Section 30123(e) of title 49, United States Code (U.S.C.) requires 
the Secretary of Transportation to prescribe a uniform system for 
grading motor vehicle tires to assist consumers in making informed 
choices when purchasing tires. In response to that congressional 
mandate, NHTSA established the Uniform Tire Quality Grading Standards 
(UTQGS) in 49 CFR 575.104.
    The UTQGS require tire manufacturers and tire brand name owners to 
grade their tires with respect to the tires' relative performance with 
respect to treadwear, traction, and temperature resistance. Treadwear 
grades are shown by numbers, such as 100, 160, and 200, with the higher 
numbers indicating greater treadwear performance. The traction grades 
are indicated by AA, A, B, and C, with AA representing the highest 
performance characteristics and C the lowest. The temperature 
resistance grades are indicated by the letters A, B, and C, with A 
representing the best performance and C indicating the minimum level of 
performance necessary to comply with Federal motor vehicle safety 
    The UTQGS provide that treadwear grades are developed first by 
running the tires being graded, called ``candidate tires,'' over a 
selected 400-mile segment of public highway outside San Angelo, Texas. 
After an 800-mile ``break-in'' run, the candidate tires are driven over 
the test course for a total of 6,400 miles in test convoys composed of 
4 passenger cars and/or light trucks. Each driver remains in the same 
position within the convoy. The vehicles are regularly rotated among 
the 4 positions in the convoy as are the positions of the tires on the 
test vehicles so that each candidate tire gets equal time with each 
driver, each vehicle, and each wheel position.

[[Page 33482]]

    Special tires known as ``course monitoring tires'' (CMT) are used 
as the control in grading candidate tires. CMTs are specially designed 
and built to American Society for Testing and Materials (ASTM) standard 
E1136 to have particularly narrow limits of variability.\1\ Until the 
amendments to the UTQGS published in a final rule on September 9, 1996 
(61 FR 4737), whenever the agency procured a new batch, or lot, of 
CMTs, we established a new base course wear rate (BCWR) for that lot. 
We established the BCWR, measured in mils per thousand miles, by 
running tires from the new lot of CMTs over the 6,400-mile test course, 
in the same manner as candidate tires, with tires from the previous 
batch of CMTs. We determined a course severity adjustment factor (CSAF) 
for the new CMTs by dividing the BCWR for the old CMTs by the average 
wear rate of the old CMTs in the test. The wear rate of the new CMTs 
was then multiplied by the CSAF to determine the adjusted wear rate 
(AWR) of the new CMTs. That value then became the BCWR for the new 

    \1\ The designation ``E1136'' refers to the standard 
specification of materials and construction practices codified by 
ASTM as suitable for control tires for scientific experimentation.

    Once the BCWR for the new CMTs was established, the new CMTs were 
used to grade candidate tires. Upon completion of the 6,400-mile test, 
the BCWR was divided by the average wear rate of the CMTs to determine 
the CSAF for the candidate tires. That factor was then applied to the 
wear rates of the candidate tires to obtain the AWR of the candidate 
tires. That AWR was then extrapolated to the point of wearout 
(considered to be \1/16\th inch of remaining tread depth). The 
resultant value was then converted to the treadwear rating of the tire.
    The BCWR was originally intended to provide a common baseline by 
which to grade candidate tires by relating all new CMTs to the original 
lot of CMTs. We noted, however, that the BCWRs of successive new lots 
of CMTs steadily declined over the years. The trend has been that every 
time a fresh CMT of the new lot was tested in the same convoy with an 
old CMT, the fresh CMT consistently experienced a lower wear rate than 
the old CMT. The first lot of CMTs that we procured in 1975 were 
commercially-available Goodyear Custom Steelguards that yielded a BCWR 
of 4.44. The lot of ASTM E-1136 CMTs that we procured in 1995, on the 
other hand, produced a BCWR of 1.34. Table I shows the consistent 
decline in wear rate for each new lot of CMTs.

                           CMT Wear Rate and Base Course Wear Rate Adjustment Factors
                                                               Measured                 Adj. wear
         Year                Manufacturer          Series     wear rate       CSAF         rate         BCWR
1975.................  Goodyear...............      Batch 1         4.44          1.0         4.44          4.44
1979.................  Goodyear...............      Batch 1         4.08         1.09         4.44  ............
1979.................  Goodyear...............      Batch 2         3.82         1.09         4.16          4.16
1980.................  Goodyear...............      Batch 2         5.29         0.79         4.16  ............
1980.................  Goodyear...............      Batch 3         4.76         0.79         3.74          3.74
1984.................  Goodyear...............      Batch 3         4.22         0.89         3.74  ............
1984.................  Uniroyal...............         4000         3.27         0.89         2.90          2.90
1987.................  Uniroyal...............         4000         5.96         0.49         2.90  ............
1987.................  Uniroyal...............        71000         4.56         0.49         2.22          2.22
1989.................  Uniroyal...............        71000         5.01         0.44         2.22  ............
1989.................  Uniroyal...............        91000         4.84         0.44         2.14          2.14
1991.................  Uniroyal...............        91000         6.24         0.34         2.14  ............
1991.................  ASTM E1136.............       010000         4.94         0.34         1.70          1.70
1991.................  ASTM E1136.............       010000         6.96         0.24         1.70  ............
1992.................  ASTM E1136.............       110000         6.65         0.24         1.62          1.62
1992.................  ASTM E1136.............       110000         5.83         0.28         1.62  ............
1992.................  ASTM E1136.............       210000         5.60         0.28         1.56          1.56
1993.................  ASTM E1136.............       210000         7.21         0.22         1.56  ............
1993.................  ASTM E1136.............       310000         6.80         0.22         1.47          1.47
1995.................  ASTM E1136.............       310000         6.47         0.23         1.47  ............
1995.................  ASTM E1136.............       410000         5.91         0.23         1.34          1.34

    In replacing CMTs from the original lot procured in 1975, we note 
that the greatest difference in the AWR between nominally identical 
CMTs of different ages was about 30 percent. This occurred in 1987 when 
the old CMTs had been stored for about 3 years. The least difference in 
the AWR between nominally identical CMTs of different ages was about 4 
percent that occurred in the second 1992 replacement. At that time, the 
old CMTs had been stored less than a year. Table I also shows that the 
treadwear rate disadvantage of the aged CMTs at replacement varied 
considerably from a linear relationship with age. This could suggest 
that the rate may have been exacerbated by actual batch differences of 
the commercial tires used as CMTs prior to 1991.
    The significance of the decrease in the BCWR rate is that as the 
BCWR decreased, the treadwear grades of candidate tires increased. 
Consequently, the newer treadwear grades have increased to the point 
that they are no longer a reliable indicator of actual treadwear 
performance when compared to tires tested with higher BCWRs.
    To correct this problem, we froze the BCWR at 1.34 mils in the 
final rule of September 9, 1996 (61 FR 47437), believing that freezing 
the BCWR at that figure would significantly reduce, if not eliminate, 
any variation in the grading between lots. We also believed that the 
use of ASTM E1136 tires that are produced with strict quality control 
would also contribute to reduction of any lot-to-lot variations. We 
stated, however, that we had requested the assistance of the ASTM F9 
committee in devising a better treadwear test and that we would request 
data in a future rulemaking on the effects of tire aging on treadwear 
performance and storage procedures to reduce aging.

[[Page 33483]]

(2) Notice of Proposed Rulemaking

    On June 5, 1998, we published a Notice of Proposed Rulemaking 
(NPRM) proposing to revise the treadwear testing procedures of the 
UTQGS to ensure the consistency of treadwear grades from one year to 
the next. \2\ To achieve that result, we proposed to revise the 
procedure for calculating the BCWR by directly comparing the wear rates 
of CMTs with the wear rates of the candidate tires. Specifically, we 
proposed to measure the wear rates of CMTs 4 times per year, then use 
the average wear rate from the last 4 quarterly CMT tests as a basis 
for the BCWR. We also proposed that CMTs used to determine the wear 
rate be no more than 6 months old at the commencement of the test and 
that the difference in production dates of the CMTs being tested be not 
greater than 3 months. If CMTs being tested were more than 6 months 
old, we proposed that the average wear rate be reduced by 10 percent.

    \2\ The NPRM originally called for a comment closing date of 
August 4, 1998. At the request of the Rubber Manufacturers 
Association, however, we extended the comment period until October 
5, 1998 (63 FR 41538, August 4, 1998).

B. Comments on the NPRM

    We received 2 comments on the NPRM, one from the Rubber 
Manufacturers Association (RMA), and the other from Uniroyal Goodrich 
Tire Manufacturing (Uniroyal).

 1. General

    RMA opposed the proposals in the NPRM, stating that our action in 
freezing the BCWR at 1.34 in the final rule of September 9, 1996 was 
sufficient to solve the treadwear inflation problem. Uniroyal generally 
supported the agency's intent in trying to ensure the consistency of 
the treadwear grades from year to year, but believed that this can be 
accomplished more efficiently than by the procedures that we proposed.
    Both opposed our proposal to require that CMTs be not more than 6 
months old when tested to determine the BCWR, arguing that that 
requirement would increase the costs of production, shipping, and 
storage for all manufacturers with no additional benefit for consumers. 
Uniroyal, the sole current manufacturer of E-1136 tires, stated that 
having to test CMTs that are 6-months old and within 3 months' 
production dates of each other would mean that testers would specify 
the most recent CMTs rather than take a chance on reducing their wear 
rates by 10 percent. This would require that CMTs be produced on a 
quarterly basis. Uniroyal stated that E-1136 tires are already produced 
in extremely small quantities and that more frequent production would 
be logistically impossible. RMA stated that the complexities associated 
with coordination, production, shipping, storage, and testing of CMTs 
and candidate tires within a 6-month period is not realistic. Both 
commenters agreed that the cost and logistical problems of producing E-
1136 tires so frequently and in such small quantities would increase 
the unit cost of such tires by a factor of 3 to 4 and could result in 
less lot-to-lot consistency.
    Both commenters supported a requirement that CMTs be tested within 
1 year after production. RMA stated that if the proposals in the NPRM 
are not withdrawn, it requested that no penalties be applied to tires 
tested within 1 year of production. RMA argued that the aging 
characteristics of CMTs and candidate tires would contribute to a 
``leveling effect'' which, together with the logistical restrictions of 
production, shipping, and storage, would minimize any difference in 
tread life during the first year. RMA stated, however, that for CMTs 
older than 1 year, any penalty should be no more than 5 percent. 
Uniroyal recommended that E-1136 CMTs be utilized for testing up to 1 
year after production, with no more than 3 months' difference in 
production dates between the tires tested.

2. Additional Uniroyal Comments

    a. Uniroyal suggested using a linear relationship to adjust for 
aging of CMTs rather the ``step'' function that the agency proposed. 
Uniroyal referred to NHTSA study DOT HS 808-701, Critical Evaluation of 
UTQG Treadwear Testing & Methodology, which found an aging effect of 
approximately 5 percent per year for cave-stored tires and about 10 
percent for non-cave-stored tires. Thus, Uniroyal encouraged the 
continued use of cave storage for CMTs.
    Uniroyal recommended that tires used in NHTSA's tests be used as 
soon as they are received from the cave and the BCWR calculated as 

    ABCWR=Adjusted Base Course Wear Rate
    BCWR=Base Course Wear Rate
    TESTTWK-DOTWK CMT=Difference, in weeks, between date at 
start of test and CMTDOT
    AAF c=Age Adjustment Factor for cave-stored tires=0.05

The new adjusted base course wear rate will be obtained by using 
average wear rate from the last 4 quarterly tests conducted by NHTSA.

    (b) Since NHTSA showed in its study that CMTs that were not 
continually cave-stored aged at twice the rate of those that were, 
Uniroyal proposed the following calculation for the adjustment factor 
if the production date of the CMT is older than that of the candidate 

Thus, the grade (P) would be computed as follows:

[[Page 33484]]


    ABCWR=Adjusted Base Course Wear Rate (from a. above)
    DOTWKCMT=Difference, in weeks, between candidate tire 
and CMT
    AAF o=Age Adjustment Factor for tires stored at test site after 
leaving cave=0.10

    If the candidate tire is equal to or older than the CMT tire, no 
adjustment is made.
    c. NHTSA should measure the CMT wear rate at least 4 times per year 
and include CMTs approximately one year old in their measurements. The 
inclusion of older CMTs in these measurements would result in a long 
term record of the aging effect and verify (or not) the approximately 5 
percent per year age effect reported in DOT HS 808-701.

C. Discussion

    For the past few years, NHTSA has been studying various ways to 
arrest the consistent decline in the BCWR that we believe has been the 
primary cause of the inflation that has plagued the treadwear grading 
system almost from the beginning. That treadwear grade inflation was 
the basis on which we froze the BCWR at 1.34 mils in the final rule of 
September 9, 1996 (61 FR at 47441), which became effective March 9, 
1998. The elapsed time since then has not given us sufficient data on 
which to determine whether the freezing of the BCWR has had the desired 
effect of arresting the treadwear grade inflation altogether, although 
preliminary indications are that it has had a very positive effect on 
the problem. In addition to contributing to the arrest of the treadwear 
grade inflation, however, the procedures specified in this final rule 
are intended to provide CMT replacement procedures that would be valid 
in all circumstances. We could use these procedures, for example, if 
ASTM changed its design specifications of the E-1136 tires; if E-1136 
tires became unavailable and we were required to substitute other tires 
for use as CMTs; or in the event of a significant change in the surface 
of the test road course. Finally, these procedures will enable us to 
test the assumption of batch uniformity of ASTM-specification tires.
    NHTSA is persuaded by the comments of the RMA and Uniroyal that it 
is not logistically feasible to produce E-1136 tires as frequently and 
in such small lots as would be necessary to consistently provide CMTs 
that are less than 6 months old. We have historically procured about 
200 CMTs per year, retaining 12 for our own use and providing the 
remainder to other testers. In making the CMT test runs 4 times per 
year, we will now consume 64 CMTs per year, but the other testers are 
expected to consume about the same number as before. Therefore, the 
increase in the number of CMTs consumed per year is relatively small 
and not enough to justify Uniroyal's having to make more production 
runs of CMTs than before, with the additional logistical problems of 
lot-to-lot consistency, storage, and shipping.
    Because of Uniroyal's production and logistical constraints on the 
manufacture of E-1136 tires, we have decided that the most practical 
solution would be to require that CMTs used in establishing the BCWR be 
less than 1 year old, instead of not more than 6-months old as we 
proposed. Further, we will not require that the CMTs used in the 
testing have production dates within 3 months of each other, nor will 
we require the 10 percent adjustment for tires over the prescribed age 
since this could create a demand for newer tires that would disrupt 
Uniroyal's production schedule. We are, however, requiring that CMTs be 
cave-stored until used \3\ and that, in addition to being not more than 
1 year old, the CMTs must be used within 2 months after being removed 
from cave storage. The 2-month requirement is intended to minimize any 
degradation while in uncontrolled storage conditions. The aging of up 
to 1 year in the cave could result in a degradation of up to 5 percent, 
an amount that we have decided to accept under the circumstances as the 
best compromise available within the economic constraints of the CMT 
supply system.

    \3\ Uniroyal ships its E-1136 tires immediately after production 
to a storage facility located in a cave in the Ozark mountains. This 
facility has a constant temperature of about 60  deg.F. and is 
remote from ozone-producing electrical equipment.

    Although the rate of treadwear degradation due to aging is not an 
exact science, our experience has been that tires stored outside the 
cave degrade at approximately 10 percent per year, while tires stored 
under the controlled climatic conditions of the cave degrade at a 
significantly lower rate, no more than a nominal 5 percent. The above 
computations that Uniroyal suggested would compensate for that possible 
5 percent aging degradation, if meticulous records were kept of the 
amount of time each CMT spent in the cave and in uncontrolled storage 
and if our estimate of the aging effect were accurate. We believe that 
the proposed Uniroyal computation is too complicated in relation to the 
small increase in accuracy. Therefore, for the sake of simplicity and, 
as stated above, considering that the treadwear measurement is not a 
precision test, we are willing to accept the possibility of tire 
degradation of up to 5 percent, which might result in the slight 
overgrading of candidate tires. Accordingly, we adhere to the formula

P = Projected mileage\*\BCWRn/402

that we proposed in the NPRM.
    In summary, this final rule revises the procedure for measuring the 
wear rate of CMTs by running them over the test course 4 times per 
year, then using the average wear rate from the last 4 quarterly CMT 
test runs as a basis for the BCWR. The CMTs used in the test runs must 
be not more than 1 year old at the commencement of the test and must be 
used within 2 months after being withdrawn from storage.
    This final rule makes one additional change. NHTSA has been leasing 
a warehouse to store the CMTs for sale to other testers. Given the 
amendments made by this final rule, NHTSA need no longer store the CMTs 
for the testers. They can purchase tires directly from the manufacturer 
for less than what NHTSA was charging. Accordingly, we are amending 
575.104(e)(1)(ii) to delete the sentence stating that CMTs are 
available from NHTSA.

Rulemaking Analyses and Notices

a. Executive Order 12866 and DOT Regulatory Policies and Procedures

    This document was not reviewed under Executive Order 12866,

Regulatory Planning and Review

    NHTSA has analyzed the impact of this rulemaking action and has 
determined that it is not ``significant'' under the DOT's regulatory 
policies and

[[Page 33485]]

procedures. This action changes the calculation for determining the 
base course wear rate of course monitoring tires which is, in turn, 
used to determine the treadwear grade of candidate tires under the 
Uniform Tire Quality Grading Standards. This action does not impose any 
additional costs on motor vehicle or tire manufacturers, distributors, 
or dealers. Instead, it permits tire manufacturers greater flexibility 
in their testing programs and could result in slightly lower costs by 
permitting them to procure course monitoring tires directly from the 
manufacturer rather than through NHTSA, as has been the practice in the 
past. Specifically, NHTSA has been leasing a warehouse to store the 
CMTs for sale to other testers. We have charged them a markup on each 
tire to cover our storage and handling expenses. Given the amendments 
made by this final rule, NHTSA need no longer store the CMTs for the 
testers. They can purchase tires directly from the manufacturer for 
less than what NHTSA was charging, which also saves NHTSA the time, 
trouble, and expense of storage and handling. We estimate that this 
will save the tire companies approximately $24,000 per year. 
Accordingly, because the cost savings are minimal, the agency did not 
prepare a full regulatory evaluation.

b. Regulatory Flexibility Act

    The agency has considered the effects of this rulemaking action 
under the Regulatory Flexibility Act, 5 U.S.C. 601, et seq. I hereby 
certify that this rulemaking action will not have a significant impact 
on a substantial number of small entities.
    The following is the agency's statement providing the factual basis 
for the certification (5 U.S.C. 605(b)). The amendments proposed herein 
will primarily affect manufacturers of passenger car tires. The Small 
Business Administration (SBA) regulation at 13 CFR part 121 defines a 
small business in part as a business entity ``which operates primarily 
within the United States'' (13 CFR 121.105(a)).
    SBA's size standards are organized according to Standard Industrial 
Classification (SIC) codes. SIC code No. 3711, Motor Vehicles and 
Passenger Car Bodies, has a small business size standard of 1,000 or 
fewer employees. SIC code No. 3714, Motor Vehicle Parts and 
Accessories, has a small business size standard of 750 or fewer 
    The amendments in this rulemaking action merely change the testing 
procedure for and calculation of the treadwear grade under the Uniform 
Tire Quality Grading Standards. The purpose of this new procedure is to 
arrest the treadwear grade inflation that has been experienced over the 
past several years. The amendments will make it necessary for NHTSA to 
conduct additional testing to determine the base course wear rate from 
which treadwear grades are calculated by tire manufacturers. The 
amendments, however, will not impose any additional requirements or 
burdens on tire manufacturers, most of which do not qualify as small 
businesses under SBA guidelines. Thus, the new procedures will not 
result in any increase in costs for tire manufacturers, small 
businesses, or consumers. Accordingly, there will not be any 
significant impact on small businesses, small organizations, or small 
governmental units by the amendments in this final rule. Thus, the 
agency has not prepared a final regulatory flexibility analysis. Annual 
expenditures from this final rule will not exceed the $100 million 

c. Executive Order 13132 (Federalism)

    The agency has analyzed this rulemaking in accordance with the 
principles and criteria contained in Executive Order 13132 and has 
determined that it does not have sufficient federalism implications to 
warrant consultation with State and local officials or the preparation 
of a federalism summary impact statement. The final rule has no 
substantial effects on the States, or on the current Federal-State 
relationship, or on the current distribution of power and 
responsibilities among the various local officials.

d. National Environmental Policy Act

    NHTSA has analyzed this rulemaking action for the purposes of the 
National Environmental Policy Act and has determined that this 
rulemaking action will not have any significant impact on the quality 
of the human environment.

e. Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1980, Pub.L. 96-
511, NHTSA states that there are no information collection requirements 
associated with this rulemaking action.

f. Civil Justice Reform

    The amendments made by this final rule will not have any 
retroactive effect. Under 49 U.S.C. 30103(b), whenever a Federal motor 
vehicle safety standard is in effect, a state or political subdivision 
thereof may prescribe or continue in effect a standard applicable to 
the same aspect of performance of a motor vehicle only if the standard 
is identical to the Federal standard. However, the United States 
government or a state or political subdivision of a state may prescribe 
a standard for a motor vehicle or motor vehicle equipment obtained for 
its own use that imposes a higher performance requirement than that 
required by the Federal standard. Section 30161 of Title 49, U.S. Code 
sets forth a procedure for judicial review of final rules establishing, 
amending or revoking Federal motor vehicle safety standards. A petition 
for reconsideration or other administrative proceedings is not required 
before parties may file suit in court.

List of Subjects in 49 CFR Part 575

    Consumer information, Labeling, Motor vehicle safety, Motor 
vehicles, Rubber and rubber products, Tires.

    In consideration of the foregoing, 49 CFR Part 575 is amended as 


    1. The authority citation for Part 575 continues to read as 

    Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; 
delegation of authority at 49 CFR 1.50.

    2. Section 575.104 is amended by revising paragraph (e)(1)(ii), 
paragraph (e)(2)(ix)(C), and paragraph (e)(2) (ix)(F), to read as 

Sec. 575.104  Uniform tire quality grading standards.

* * * * *
    (e) * * *
    (1) * * *
    (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.
* * * * *
    (2) * * *
    (ix) * * *
    (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 

    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

[[Page 33486]]

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.

* * * * *
    (F) Compute the grade (P) of the NHTSA nominal treadwear value for 
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.
* * * * *

    Issued on May 11, 2000.
Rosalyn G. Millman,
Acting Administrator.
[FR Doc. 00-12873 Filed 5-23-00; 8:45 am]