RMA Says Scrap Study Shows Tyre Age Not a Performance Issue

(Akron/Tire Review) A study undertaken in the USA by the Rubber Manufacturers Association (RMA) claims there is no correlation between the end of a tyre’s “safety performance” and its chronological age. RMA released its study data earlier this week after examining some 14,000 scrapped P-metric and LT-metric tyres late last year, comparing each tyre’s date of manufacture to the date it was examined.

The study showed a consistent pattern of retirement for the scrapped units. Tyre date codes showed that the sample included tyres that were from one to 16 years of age. “If chronological age was a determining factor in tyre performance, the data would have shown a spike of tyres removed from service after a particular time,” RMA said in a statement.

The study, said the RMA, did not consider reasons why the examined scrap tyres were taken out of service. The study only compared the examined tyre’s manufacture date (from DOT codes) to the date the tyre was examined. According to RMA, the on-site scrap tyre inspections took place between Oct. 18 and Dec. 21, 2005.

“If age was a sole factor in determining tyre service life, our data would have shown a significant number of tyres being removed from service at a particular point,” Laurie Baulig, RMA’s general counsel, said. “Our data showed no magic date when tyres are removed from service.”

While the RMA claims it did not trace the history of the tyres it examined, it says it is “reasonably certain” that the thousands of scrap units it looked at had been taken out of service with two to three weeks prior to examination.

Examiners did record the measurable tread depth and condition of the scrap tyres – including the presence of any repairs – but the study did not consider the reasons why any of the tyres were taken out of service. “We wanted to focus on measurable, recordable things that we could see,” said an RMA spokesman.

The study also found that:

• 42% of tyres in the study had tread at or below tread wear indicators. Among tyres older than one-year, 59% were removed due to wear-out.
• 25% exhibited signs of road hazard damage.
• 17% had been repaired, and of the repairs observed 87% were improper – not performed with a plug and internal patch as specified by RMA tyre repair guidelines.

RMA said the study was not intended to “be a forensic study or about the safety performance” of the tyres that were examined. “We wanted to see if there was a ‘magic removal date,’ some consistent timeframe that might indicate if tyre safety performance ends at a set time.”

Study examiners were “trained tyre technicians” supplied by RMA tyre company members. RMA declined to say which companies provided examiners. The technicians took two to three days to examine and record data on some 2,000 tyres at each of 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, said RMA.

Only P- and LT-metric tyres were considered, and all were radials.

RMA said the study data has been shared with the National Highway Traffic Safety Administration (NHTSA), which is considering the tyre aging issue.