HILTON HEAD, S.C.—The National Highway Traffic Safety Administration could decide as early as this spring whether to pursue rulemaking on tire aging, a NHTSA official told the audience at the 30th annual Clemson University Tire Industry Conference, held recently at Hilton Head.
A final rule updating federal truck and bus tire safety standards can be expected this year, as can the long-awaited labeling and consumer information portions of the tire fuel efficiency final rule, said Abby Morgan, a NHTSA safety standards engineer.
The Rubber Manufacturers Association regards consumer tire information and standards from the tire fuel efficiency rule as one of its current 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 separate phases of tire aging tests on light vehicle tires since 2002, beginning when agency crash data suggested a trend of higher rates of failure among older tires, Morgan said.
“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, Morgan said.
“Five weeks in an oven equals four years in a hot environment,” she said.
The agency noted endurance test failures after oven aging, Morgan said. However, tires manufactured according to Federal Motor Vehicle Safety Standard 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 www.regulations.gov in Docket NHTSA-2005-21276. An agency report summarizing tire aging tests and NHTSA's next steps on the issue will be added to that docket this spring, Morgan said.
FMVSS No. 119, the safety standard for truck and bus tires, has been in effect since 1973, according to Morgan. But the Transportation Recall Enhancement, Accountability and Documentation Act of 2000 mandated an update of all tire safety standards, and FMVSS 139 for passenger tires came out in 2003.
NHTSA published a proposed rule on truck tires in September 2010. 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, Morgan said.
It published a supplemental notice of proposed rulemaking in January 2013, and it expects to issue a final rule this year, she said. Meanwhile, Docket NHTSA-2010-0132 contains all the information on this rulemaking, she said.
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), Morgan said.
It took 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, she said.
Full implementation of the consumer information program will be set for six months after its final publication, she said.