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WASHINGTON, D.C., May 23, 2006 - A comprehensive study of more than 14,000 scrap tires shows that chronological age alone cannot determine when a tire is removed from service.
The Rubber Manufacturers Association inspected tires at seven large scrap tire processors in seven states and recorded the tires’ date code and tread depth as well as whether the tires had been repaired or had any visible damage. The study data has been shared with the National Highway Traffic Safety Administration (NHTSA).
RMA initiated the study late last year. In June 2005, RMA wrote to NHTSA urging the agency to examine whether a relationship existed between a tire’s safety performance and its chronological age. In the letter, RMA also agreed to work with the agency to provide information about chronological tire age.
“We believe that a good starting point for a discussion about chronological age and tires was to examine tires that had been removed from service,” said Laurie Baulig, RMA general counsel.
RMA’s scrap tire survey examined more than14,000 tires that had been removed from service. The date codes on the tires showed that the survey sample contained tires from one to sixteen years old. If chronological age was a determining factor in tire performance, the data would have shown a spike of tires removed from service after a particular time.
“If age was a sole factor in determining tire service life, our data would have shown a significant number of tires being removed from service at a particular point,” Baulig said. “Our data showed no magic date when tires are removed from service.”
Other study observations included:
- 42 percent of tires in the study were removed due to wear-out (had tread at or below tread wear indicators). After the first year of service, 59 percent of tires in the study were removed due to wear-out.
- 25 percent of the tires had road hazard damage.
- 17 percent of the tires had been repaired.
- Alarmingly, 87.5 percent of the observed tire repairs were improper – not performed with a plug and internal patch as specified by RMA tire repair guidelines.
The RMA scrap tire study encompassed 14,271 randomly selected tires observed at seven scrap processing facilities in five geographic regions of the country. The seven sites were located in Arizona, California, Florida, Illinois, Massachusetts, Oregon and Pennsylvania. Trained tire technicians from RMA member companies painstakingly observed approximately 2,000 tires at each site and recorded manufacture date code, tire wear and any visual damage or tire repair.
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The Rubber Manufacturers Association is the national trade association for the rubber products industry. Its members include more than 100 companies that manufacture various rubber products, including tires, hoses, belts, seals, molded goods, and other finished rubber products. RMA members employ over 120,000 workers and account for more than $21 billion in annual sales.