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NHTSA may pursue tire-aging rule soon

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Clemson University photo Abby Morgan, safety standards engineer, National Highway Traffic Safety Administration

HILTON HEAD ISLAND, S.C. (June 4, 2014) — The National Highway Traffic Safety Administration (NHTSA) could decide as early as this spring whether to pursue rulemaking on tire aging, according to Abby Morgan, NHTSA safety standards engineer.

Speaking at the 30th annual Clemson University Tire Industry Conference, Ms. Morgan said a final rule updating federal truck and bus tire safety standards also can be expected this year, as can the long-awaited labeling and consumer information portions of the tire fuel-efficiency final rule.

The Rubber Manufacturers Association (RMA) regards consumer tire information and standards from the tire fuel-efficiency rule as two of its key issues, along with proper tire repair, tire inflation pressure maintenance and banning unsafe used tires from the road, said Tracey Norberg, RMA senior vice president and general counsel.

NHTSA has run five phases of tire-aging tests on light vehicle tires since 2002, Ms. Morgan said, beginning when agency crash data suggested a trend of higher rates of failure among older tires.

“We noticed a phenomenon regarding the degradation of the material properties of a tire,” she said. “Over time, the degradation can compromise a tire's structural integrity.”

The relationship between tire age and tire failure seems particularly strong in warm-weather states such as Arizona, Florida, Texas and Southern California, she said.

NHTSA experimented with multiple oven temperatures, durations and inflation gas contents before developing an oven aging test procedure it found satisfactory, according to Ms. Morgan. “Five weeks in an oven equals four years in a hot environment,” she said.

The agency noted endurance test failures after oven aging, according to Ms. Morgan. However, tires manufactured according to Federal Motor Vehicle Safety Standard (FMVSS) No. 139 — the revised safety and endurance standard for passenger and light truck tires — perform better after oven aging than pre-139 tires, she said.

Reports on Phases 1, 3, 4 and 5 of tire-aging testing can be found at in Docket NHTSA-2005-21276, Ms. Morgan said. An agency report summarizing tire-aging tests and NHTSA's next steps on the issue will be added to that docket this spring.

FMVSS No. 119, the safety standard for truck and bus tires, has been in effect since 1973, according to Ms. Morgan, but the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act of 2000 mandated an update of all tire safety standards, and FMVSS 139 for passenger tires came out in 2003, she said.

NHTSA published a proposed rule on truck tires in September 2010, Ms. Morgan said. Among the key changes proposed in the document were a new high-speed test, an upgraded endurance test and new maximum speed labeling.

The agency conducted additional endurance testing on truck tires in 2011 and 2013, to evaluate the performance of mixed-service tires and assess the appropriateness of a 50-mph drum test speed, Ms. Morgan said.

Clemson University/Tire Industry Conference photo Tracey Norberg, senior vice president and general counse, Rubber Manufacturers Association

It published a supplemental notice of proposed rulemaking in January 2013, and expects to issue a final rule this year, she said. Meanwhile, Docket NHTSA-2010-0132 contains all the information on this rulemaking.

The partial final rule for tire fuel-efficiency grading came down four years ago, but it took time to respond to petitions for reconsideration, conduct necessary consumer research and assign a rolling resistance test laboratory (Smithers Rapra), the NHTSA official said.

It took many months to research the variability of rolling resistance, traction and treadwear ratings under the rule, she said. However, a consumer information program proposal has been developed, and will be outlined in a supplemental proposed rule.

Full implementation of the consumer information program will be set for six months after its final publication.

The final rule on consumer tire ratings and information should be the final piece of the puzzle locking in with standards for tire fuel efficiency and wet traction, according to Ms. Norberg.

“We were out in front on an issue we felt would make the industry better,” she said. The RMA wrote the tire fuel-efficiency provisions that became law in the Energy Independence and Security Act in December 2007.

A 2006 National Academy of Sciences study showed that a 10-percent reduction in rolling resistance translates to a fuel-consumption reduction of 1 or 2 percent, according to Ms. Norberg. Yet consumers still have no real way of choosing fuel-efficient tires, she said.

“Now you can go to any tire manufacturer's website and find information on the rolling resistance of their tires. But there's still no way to compare Tire A with Tire B.”

Any good tire consumer education program should be based on proper tire maintenance, Ms. Norberg said. “You can drive the best tires in the world, but if you're not inflating or aligning them properly, you won't get the best out of those tires.”

The features the RMA would like to see in the tire fuel-efficiency rating system include:

  • A five-bin rating system for traction, treadwear and rolling resistance;
  • A rating based on the rolling resistance coefficient, which would offer consumers a broader range of choices in each tire category;
  • The use of “traction” and “treadwear” in the ratings system instead of vaguer terms such as “safety” and “durability,” and
  • The establishment by NHTSA of a rolling-resistance reference machine based on Standard 28580 from the International Standards Association.

Minimum rolling-resistance standards will eliminate the least fuel-efficient tires from the U.S. passenger tire market, Ms. Norberg said. At the same time, wet-traction minimum standards should be consistent with draft global technical standards for passenger tires, and should be designed to ensure that the rolling-resistance standard is not achieved at the expense of wet traction, she said.

Other nations already have adopted, or are in the process of adopting, minimum standards for tire fuel efficiency and wet traction, according to Ms. Norberg.

“Catching up to other nations will help ensure that the United States does not become a dumping ground for lower-performing tires,” she said.

Meanwhile, on the state level, the RMA continues to support legislation that would prohibit unsafe used tires from going back into service, according to Ms. Norberg.

The RMA's model used tire legislation is based on the association's Tire Information Service Bulletin on used passenger and light truck tires, she said. The RMA does not advocate a complete ban on used tires, only penalties for putting unsafe used tires on the road, she added.

According to the provisions of the RMA bill, used tires should not be installed on vehicles if:

  • Their tread depths are 2/32nd inch or less;
  • They have any damage exposing the reinforcing plies;
  • They have been repaired improperly;
  • They show evidence of previous tire sealant use;
  • Their tire identification numbers have been removed or defaced;
  • They were involved in a safety recall;
  • They have inner liner or bead damage; or
  • They have bulges, irregular treadwear or other signs of internal separation.

The RMA is targeting Florida, Georgia and South Carolina as the states for introduction of used tire legislation, Ms. Norberg said.


Reporter Miles Moore can be reached at



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