American tire companies have helped to defeat proposed laws in eight states that would require inspection of tires for age. Safety advocates say aging increases the risk of dangerous tire failures.
Ford, GM and Chrysler all urge motorists to replace of tires that are six years of age or older because of the possibility the rubber in them could degrade and create a dangerous situation in which the tire loses its tread.
"If we are thinking about a universal practice that inherently keeps you safe, six years is a good place to go," said Sean Kane, a safety consultant for several state governments and lawyers who sue tire companies.
But the tire industry trade group, the Rubber Manufacturers Association, says the six-year limit is ”an arbitrary date” not supported by facts and has hired lobbyists to defeat laws that would require mandatory inspection of tire age.
"We oppose legislation that have some sort of age limit on tires," said Dan Zielinski, executive director of the trade group.
In the most recent case, the trade group spent $36,000 on lobbyists to defeat proposed legislation in the state of Massachusetts that would have included the age of tires on regular vehicle inspections, according to ABC News' Boston affiliate WCVB, which joined other top ABC News affiliate investigative teams around the country in a national hidden camera investigation into tire safety.
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"It’s more important how a tire is used, whether it‘s maintained and how it’s stored," Zielinski said.
But even one tire company, Michelin, cautions that aged tires could be a problem, urging motorists to replace tires over 10 years old.
Safety experts say a tire can age and degrade under certain conditions even if it has not spent any time on the road.
"Over time, they become less elastic," said Kane. "And once it’s put into service it represents a significant hazard."
For consumers, determining the age of a tire can be a daunting task. The date of production can be found in a unique code at the end of 11- or 12-digit identification number on the tire’s sidewall.
But instead of the standard month/year display, the tire industry uses a week/year display.
For example, a tire produced in early June of 2010 (in the 21st week of the year) would be displayed as 2110, instead of the more common 06/10 that most consumers are accustomed to seeing.
"They did not want to put a date code on tires, specifically because they did not want to give the impression that tires might actually have a service life," said Kane, the safety consultant.
Tire age degradation is part of a first-of-its-kind special investigation launched by the National Transportation Safety Board into the hundreds of deaths each year from "tire initiated events."
"Aging does potentially play a role in the degradation of the internal structure of the tire," said Don Karol, the investigator leading the NTSB initiative.
Investigators are focused on a recent accident in Louisiana in which a 10-year-old tire on a sports utility vehicle lost its tread and the driver lost control of the vehicle and crashed into a bus carrying a high school baseball team. Though everyone on the school bus survived, the February crash killed four of five people in the SUV.
“It’s definitely a significant issue,” said the NTSB’s Karol.
Editor's Note: A previous version of this report misidentified the tire trade group. It is the Rubber Manufacturers Association.