Comments on NHTSA Federal Motor Vehicle Safety Standards on Tires
Docket Management System
U.S. Department of Transportation
Seventh Street, SW
Washington, DC 20590-0001
Re: Docket No. NHTSA-00-8011
Comments of Consumers Union of
National Highway Traffic Safety Administration
Federal Motor Vehicle Safety Standards; Tires
49 CFR Part 571
The National Highway Traffic Safety Administration (NHTSA)
has issued a notice of proposed rulemaking (NPRM) in response to the mandate
issued by Congress in the Transportation Recall Enhancement, Accountability,
and Documentation Act of 2000 (TREAD Act) for a new tire standard to replace
FMVSS 109 (passenger car tires) and FMVSS 119 (portions related to light
duty light truck tires only). The new standard will provide more appropriate
requirements for evaluating radial tires, which have virtually replaced
the bias and bias belted tires that reigned when FMVSS 109 and 119 were
issued in 1967. Current standards should be retained for bias tires, which
are still produced for special purpose, antique, and classic applications.
Congress directed NHTSA to develop new standards in late
2000 after hearings investigating hundreds of the rollover crashes involving
primarily Ford Explorers with Firestone tires revealed that NHTSAs
tire standards had not been updated since the late 1960s. Congress clearly
felt a sense of urgency about the need for new standards, directing NHTSA
to issue a final rule by June 1, 2002. We hope the agency is able to process
the public comments in an expeditious manner and issue the final rule as
soon as possible.
We are mindful of NHTSAs estimate that about "one-third
(32.8 percent) of all tires would need improvements to pass those two [Endurance
and High Speed] tests." This is a large percentage of the current
tire market, certainly, but we note that NHTSA also estimates that, "If
the cost for these improved tires were spread across the entire new light
vehicle fleet, the average new vehicle price increase would . . . be $4.09
per vehicle." NHTSA estimates the overall annual cost of these tests
for new original equipment (64 million new car tires) and replacement tires
(223 million tires), to be $282 million, for a total of 287 million tires
sold annually with the net cost per equivalent life saved estimated at
$7.2 million. The demonstrated benefit of improved tire safety performance
at less than one dollar per tire at retail is a good trade-off, one that
is long overdo.
The intention of the TREAD mandate and revised tests
was to provide stringent test methods that would encourage the development
of more robust tires (both by design and in manufactured quality) and more
appropriately challenge current radial tire technology. Without some intended
level of failure for current tires, the proposed tests could not be considered
a positive step forward. Secondly, some of the proposed test changes more
closely replicate "real world" conditions. Increased speeds in
both the proposed high speed and endurance tests replicate current typical
highway speeds and increased loads in the endurance testing convey the
added potential for increased loading of tires when applied to vehicles
such as SUVs, vans and trucks popular in the current vehicle market.
CU supports the increased performance levels required to pass the proposed
tests as a means of eliminating marginal designs and more closely representing
current application conditions.
In proposing the new tire standard under FMVSS 139, NHTSA
has reviewed the testing protocol submitted by the Rubber Manufacturers
Association (RMA) along with Global Tire Standard (GTS) 2000, which is
the harmonized standard proposed by the global auto standards community.
Michelin and Toyota provided additional procedures, which the government
reviewed and evaluated. In the NPRM, NHTSA sets out proposed test procedures
along with selected alternate procedures to be considered. The new standard
will redefine and elevate safety performance characteristics for tires
used on vehicles of GVWR of 10,000 lbs. or less. Compared with the current
standard, the tests proposed include more stringent high speed and endurance
tests; a new low pressure test requirement; a new road hazard impact test
requirement; a new bead unseating test to replace the current bead push-off
test: and a new aging test requirement. With few exceptions, these tests
are designed to be performed in laboratories using test equipment currently
used in the tire industry.
Listed below are Consumers Unions comments on the
technical merits of the proposed FMVSS 139 tests.
High Speed Test
As proposed, this procedure is intended to insure that
all tires meet minimum requirements regardless of the tires speed
rating. This testing protocol also requires that, under the conditions
specified, the maximum test speed would be just 160 kph (100 mph), which
would effectively challenge non-speed rated and speed rated tires below
R (tires carrying speed ratings corresponding to 170 kph, (106 mph) maximum.).
Though the proposed test may serve as a minimum requirement
and be appropriate for non-speed rated tires, it does not require that
higher speed rated tires (S and above), the most common on new cars, be
tested to the limits of their claimed speed capability. CU disagrees with
this approach as it does not reflect the speed capacity claim defined by
the speed symbol on the tire. CU supports a stepped speed test that will
test all speed rated tires to their maximum speed rating. Without such
tests, the higher speed ratings have little value to the consumer other
than marketing hype. Indeed, the tire industry itself has a speed schedule
that would provide testing to the tires maximum speed capability
under RMA 2000.
The high speed test is important not because it represents
realistically the speed driven by the average consumer, but because of
its ability to evaluate the tires capacity to dissipate heat, a variable
that directly affects the tires durability. CU believes that a more
appropriate title for the high speed test would be "the temperature
Indeed, the speed rating may be defined by certified
speed capability, but essentially it is a reflection of heat dissipation.
The Uniform Tire Quality Grading System (UTQGS) Temperature Rating, which
uses an A, B, and C rating system (with A the highest rating), has a similar
definition for all passenger tires. The UTQGS Temperature Test and proposed
new High Speed Test are both high speed tests and both evaluate a tires
ability to dissipate heat. Therefore, both tests evaluate the same parameter.
Unfortunately, the UTQGS temperature grade system provides redundant information
and it is sometimes contradictory to the speed rating on the tire. While
the different grades attempt to describe performance, manufacturers can
arbitrarily apply an UTQGS Grade to the tire regardless of how it performed
or what the speed rating is. Further, it appears that only A and B graded
tires could pass the new high speed test, thus limiting its usefulness.
Because of the redundancy of UTQGS temperature grading system, and
because this grade sometimes contradicts a tires speed rating, CU
recommends that NHTSA abolish the UTQGS temperature grade system
In contrast, the globally accepted alpha speed rating
system, used to run the RMA 2000 test, has 21 letters to define maximum
rated speed from 31 to 188 mph, (and one to be definable by the vehicle
manufacturer (ZR rating)). We believe that these speed rating symbols are
superior to the UTQGS grades and would better guide consumers seeking to
purchase compatible replacement tires.
As a preferred alternative to the minimum standard test,
Consumers Union recommends all tires be speed rated and then tested according
to the RMA 2000 (including the 40°C temperature adjustment) procedure.
Moreover, the RMA 2000 procedure follows GTS 2000 closely
and would provide greater promise for reaching global harmonization than
the proposed FMVSS 139 test. CU acknowledges that should the RMA 2000 type
high speed test be adopted, it would require revision of FMVSS 110 to define
reserved load capacity limits differently, as they could no longer reference
FMVSS 139 High Speed test conditions.
For the sake of consistency to other FMVSS 139 regulations,
CU believes that testing conditions, as specified by RMA 2000 should be
raised to 40°C. Indeed, NHTSA found 40°C. typical to daytime
temperatures in the southern regions of the U.S. during the summer. This
would be a minor change and well within the tolerance defined by NHTSA.
For the RMA 2000 proposed High Speed test, the NPRM contains
no data to either support or challenge the effect of load (80% of maximum
load for a passenger tire, 90% of maximum for a LT tire) or the ten minute
duration of each speed step as defined by RMA 2000. FMVSS 139 proposes
that the load be 85% of maximum and speed steps to run for 30 minutes each.
CU agrees with NHTSA that the ten minute speed steps used in RMA 2000 are
too short to evaluate high speed capability. NHTSA and RMA data indicate
that load is less influential than speed and inflation pressure in causing
failures, leading CU to conclude that the load differences between the
RMA and proposed 139 test are a non-issue. CUs conclusions are based
on the failure rates in the tested as reported in the proposed rulemaking.
CU favors an RMA 2000 type high speed test. However,
should the current FMVSS 139 proposal be adopted, the following should
FMVSS 109 High Speed, the current test, sets the load
at 88% of maximum rating. The proposed test reduces the load to 85% of
maximum rating. NHTSA argues that the slightly lower test load will not
affect the outcome of the failures based on RMA and their own research
data. The agency calls the unused portion of the tires rated maximum
load the reserve tire load (100% max load 85% max load = 15% reserve
load). As required by FMVSS 110, the load placed on a tire from the normal
load of the vehicle (curb weight plus the weight of three passengers in
a five passenger car) cannot exceed the load used in the high speed tire
test. Lowering the high speed load to 85% then dictates that vehicle manufacturers
specify less load to the tire under normal conditions of the car to give
the tire an extra margin of safety for additional loading by increasing
the reserve tire load from 12% currently to 15% for the application. CU
supports this change should the proposed high speed methodology be adopted.
Currently, testing LT designated tires for vehicles under
10,000 lbs. GVWR doesnt require high speed testing and reserve loading
requirements as all testing is based on maximum load. An additional benefit
stemming from this change, therefore, would be that light trucks would
also have the same reserve load under normal loading conditions. Affected
LT tires will have to be identified in some manner to let the manufacturer
know if it must meet FMVSS 139 or FMVSS 119 requirements.
The proposed endurance test will be appropriately
more difficult to pass, largely due to the increase in test speed from
50 to 75 mph. We support this change. Other changes from the current tests,
including higher ambient temperature (+ 2°C), higher loads (+5% and
+10% for passenger tires), and a longer test duration (+6 hours more than
FMVSS 109), collectively toughen the requirements.
The proposed Endurance test may also be expected
to achieve future global harmonization based on its similarity to GTS 2000
and RMA 2000 procedures.
At this time, NHTSA is proposing a low pressure test
as a link to the tire pressure monitoring system (TPMS) required on new
vehicles effective November 1, 2003.
NHTSA asks for comments on a low pressure TPMS
test and a low pressure high speed test.
CU recently conducted evaluation of 36 passenger all-season
tire models for air loss (see attached). One hundred eight tires (three
of each model) were mounted on new rims, carefully checked for leakage
and monitored for air loss over a one year period. On average, the 36 models
lost 6.6 psi over a years time with the worst model losing 12.6 psi
in that same period. These data clearly indicate that popular tire models
can easily reach monitoring system thresholds in less than a years
time and combined with the failure rates as indicated above should be considered
when establishing TPMS thresholds and any other low pressure testing conditions.
In addition, the data collected in the CU air loss evaluation
also clearly showed the tendency of multiple tires of a single model to
lose air at a fairly uniform rate. Such behavior and uniformity of air
loss was one of CUs greatest concerns in the allowing of the indirect
TPMS in the recent final rulemaking as such systems would be unable to
detect major uniform air loss should like models be applied in multiple
The TPMS test NHTSA would run an additional 90 minute
test segment following the 40 hour endurance on a tire loaded to 100% maximum
load and inflated to 20 psi. The NPRM does not provide enough information
to determine when exactly the tire would be run to the low pressure conditions
following successful completion of the endurance test. We recommend that
the tire be allowed to cool down for a minimum of three hours at the ambient
test condition before starting the low pressure test. The tire inflation
should be regulated to negate any tire pressure build-up. The cool-down
period and regulated pressure ensure that all tires are run to the same
Moreover, CU believes that testing the tires for 90 minutes
at 75 mph represents too short a distance (just 112.5 miles) and is well
below the typical fuel range of most vehicles. Indeed, the fact that all
24 tires tested by NHTSA passed the test without failure indicates that
this test is not sufficiently rigorous. CU recommends that the test duration
be at least four hours at 75 mph, simulating a distance of 300 miles and
is more representative of the fuel range of a typical vehicle.
CU favors an endurance type TPMS low pressure test,
as we state above, over the high speed version also proposed, because it
is more representative of conditions consumers are likely to face. Of greater
concern, however, is the number of tire failures in the high speed version,
as noted in the proposed rulemaking. The NPRM notes that despite the lower
load at 67% of maximum, NHTSA estimated that most Q rated tires (99 mph),
63% of R rated tires (106 mph) and 30% of S rated tires (112 mph) would
not pass. This frequency of failure raises questions about the safety of
tire applications that would be allowed to approach the 20 psi condition.
Current TPMS thresholds may be set too low for high speed conditions.
NHTSA plans to adopt SAE J1981, a weighted (54 kg)
pendulum system that impacts the tire. The test is repeated for a total
of five impacts around the circumference of the tire. The test simulates
the impact the tire and wheel system might see encountering a pothole in
the road. NHTSA proposes to pass the tire if there is no visual sign of
tire failure and the tire pressure is the same as the initial test pressure.
Consumers Union believes incipient component failure could too easily go
undetected in a visual inspection. Laser holography (shearography) inspection
examines the tire internally. We believe the standard should require the
use of this technology and not rely only on a visual inspection. This technology
is also useful for all other destructive tests (endurance, high speed,
and low pressure tests).
Strength Test (Plunger)
The government is proposing elimination of the strength
test that applies a plunger into the tread of the tire, much like a tire
running over a probe in the road. Consumers Union agrees that the test
has limited merit for steel belted radial tires and even less with low
aspect ratio radial tires. The test is a valuable tool for assessing the
durability and strength of bias tires and should be retained, along with
the current FMVSS 109 requirement, for bias tires.
The current bead unseating test was designed for
bias tires and is not well suited to radial tires. NHTSA is proposing an
air loss bench test instead of an on-vehicle air loss test method, both
developed by Toyota. The proposed air loss bench test requires special
non-industry-standard equipment that applies a lateral force to the tread
of the tire, pulling the sidewall from the rim. If air loss or bead unseating
results, the tire fails the test.
NHTSA is also considering a vehicle test that measures
air loss caused by a "J turn" maneuver. While Consumers Union
supports NHTSAs intent to probe more deeply into the cause of bead
unseating, CU recommends that the agency investigate this problem more
thoroughly prior to proposing this test regulation. We recommend controlled
laboratory bench type tests as the best approach in providing bead roll
off results, which we believe would be more repeatable, more precisely
controlled, and will avoid the vehicle and surface effects that could confound
results using a "J-turn" vehicle test. We note, however, that
the data for either test are not provided in the NPRM.
The TREAD Act directed NHTSA to establish a procedure
to test the effects of tire aging, and the agency is currently looking
into ways of assessing this phenomenon. There are no industry-wide practices
for testing the effects of tire aging. Michelin submitted a proposed durability
endurance test, but it would need to be run at least 250 hours, which is
1.5 to 2 weeks; the time involved to run the test would outstrip the wheel
capacity of many tire manufacturers, but more important, it would seem
to be too long a period of time to monitor weekly production of tires.
Another test, an adhesion procedure that mechanically
tests the tensile pull to peel off the tread of the tire and would be done
after running an abbreviated endurance test, is not sufficiently repeatable
or precise. Under these circumstances, CU believes that no test is better
than a bad test. Therefore, we urge NHTSA to conduct more research to develop
a practical and efficient method of testing the effects of tire aging.
Finally, NHTSA is looking at the possibility of oven
aging or "cooking" the tire before running an endurance test.
However, such a procedure doesnt bear much resemblance to what consumers
experience in the real world with tire aging. In real world conditions,
tires do not heat up evenly, and its often the hot-spots and dynamic
flexing that define the weak link in tire design. Consumers Union believes
further investigation of a more suitable procedure is needed.
Lead time for standard implementation by the tire
Congress mandated that this new tire standard be finalized
by June 1, 2002. We are mindful of the significant number of rulemakings
NHTSA is required to complete in response to TREAD, and we understand that
each rulemaking requires a great deal of staff time and attention. Nevertheless,
we note that the due date for these comments is June 5, 2002, and they
precede a final rule, so we can assume there wont be a final rule
for several months at minimum. Consumers Union recommends that these standards,
taking into account reasonable technological and economic limitations,
become final as soon possible.
June 5, 2002
1666 Connecticut Avenue, NW
Washington, DC 20009
Senior Vice President, Technical Policy
Senior Product Safety Counsel
Senior Automotive and Tire Test Engineer
Automotive and Tire Test Engineer
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