Age alone does not determine when tires are removed from service.

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 have been shared with the National Highway Traffic Safety Administration.

The RMA initiated the study late last year. In June 2005, the RMA wrote to the NHTSA, urging the agency to examine whether a relationship existed between a tire's safety performance and its chronological age. In the letter, the RMA also agreed to work with the agency to provide information about chronological tire age.

The RMA's scrap tire survey examined more than 14,000 tires that had been removed from service. The date codes on the tires showed that the survey sample contained tires from one to 16 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. However, it was reported that the data "showed no magic date" when tires are removed from service.