Comments of Consumers Union of US Inc.
to
National Highway Traffic Safety Administration
on
Federal Motor Vehicle Safety Standards; Tires
49 CFR Part 571
RIN 2127-AI54

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 NHTSA’s 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 NHTSA’s 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 SUV’s, 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 Union’s 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 tire’s 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 tire’s 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 tire’s capacity to dissipate heat, a variable that directly affects the tire’s durability. CU believes that a more appropriate title for the high speed test would be "the temperature resistance" test.

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 tire’s 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 it’s usefulness. Because of the redundancy of UTQGS’ temperature grading system, and because this grade sometimes contradicts a tire’s speed rating, CU recommends that NHTSA abolish the UTQGS’ temperature grade system altogether.

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. CU’s 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 be considered:

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 tire’s 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 doesn’t 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.

Endurance

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.

Low Pressure

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 year’s 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 year’s 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 CU’s 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 wheel locations.

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 conditions.

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.

Tire Impact

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.

Bead Unseating

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 NHTSA’s 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.

Aging Tests

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 doesn’t 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 it’s 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 industry

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 won’t 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.

Respectfully submitted,

June 5, 2002

CONSUMERS UNION
1666 Connecticut Avenue, NW
Washington, DC 20009
202-462-6262

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Consumer’s Union Air Loss Evaluation — Passenger All-Season Tires P195/70R14