[WorkinLonghorn]

"What exactly is the problem with old tires?"

This doesn't address the exact causes,but is still enlightening;




Tires: Aging Dangerously

Copyright Ó Safety Research & Strategies, 2006


Tires, like any other rubber product, have a limited service life regardless of tread depth and use. The dangers of "aged" tires is a little known problem outside of the industry and one that is likely the cause of a significant number of tread separation problems. "Aged" tires are often unsuspectingly put into service after having served as a spare, stored in garages or warehouses, or simply used on a vehicle that is infrequently driven. In many instances these tires show no visible sign of deterioration, and absent any visible indicators, tires with adequate tread depth are likely to be put into service regardless of age.



Tire age can be determined through decoding of the required DOT number molded into the side of a tire; however, the DOT date coding is consumer unfriendly and confusing. [Decoding the DOT Number]



Following the Ford/Firestone tire investigations in 2000 the National Highway Traffic Safety Administration (NHTSA) began examining tire aging as a factor in tread belt separations and proposed a tire aging test in 2002 [Docket 2000-8011-19]. However, overwhelming industry opposition and the lack of an agreed upon aging standard led NHTSA hold further rulemaking and to begin additional research [June 26, 2003 Final Rule, Docket 03-15400-1]. As a result the agency is currently testing tires to discern possible test protocols that would ensure tires do not fail catastrophically before they wear out. This process is still several years from fruition. Following NHTSA's decision to commence additional research in 2003, SRS president Sean Kane, (formerly with Strategic Safety, LLC) began documenting a trend of catastrophic tire failures in the U.S. in which the tires were six years old or older. Kane also found important evidence that tire manufacturers have internal recommendations related to tire aging that were either never disclosed publicly. A summary of these findings along with a recommendation that NHTSA consider a tire expiration date requirement was submitted to the agency on September 17, 2003 [Docket 15400-12].



One of the most important documents disclosed to NHTSA regarding the industry knowledge of tire aging is the British Rubber Manufacturers Association (BRMA), which consists of the same tire manufacturers who are present in the U.S. market, recommended practice dated June 5, 2001. The BRMA's recommended practice on tire aging states



"BRMA members strongly recommend that unused tyres should not be put into service if they are over 6 years old and that all tyres should be replaced 10 years from the date of their manufacture."



It also notes that environmental conditions like exposure to sunlight and coastal climates, as well as poor storage and infrequent use accelerate the aging process.



"In ideal conditions, a tyre may have a life expectancy that exceeds 10 years from its date of manufacture. However such conditions are rare."



The BRMA document goes on to say that aging may be identified by small cracks in the tire sidewall, however,



"'[a]geing' may not exhibit any external indications and, since there is no non destructive test to assess the serviceability of a tyre, even an inspection carried out by a tyre expert may not reveal the extent of any deterioration."



Further, Kane's comments to NHTSA disclosed little-known warnings in the owner's manuals of German vehicles (i.e., Mercedes, BMW, Audi, VW) and Toyota that tires older than six years posed dangers. This information, combined with a number of other technical documents provide clear evidence that the tire and vehicle manufacturers are aware of, and likely in the possession of important data and testing upon which these obscure findings were based. However, none of this information was disclosed to NHTSA in response to its request for comments about tire aging.



As a result of our continued research into tire aging, SRS petitioned NHTSA on November 5, 2004 requesting the agency take three important interim steps to address the tire age problem. We requested (1) a Consumer Advisory alerting the public to the hazards, (2) NHTSA request specific information from the tire and vehicle manufacturers that will help with further evaluation of the problem, and (3) petitioned to require a date of manufacture molded in both sides of the tire in a non-coded fashion.



SRS is continuing to document the scope and magnitude of the tire aging problem as well as its investigation into what is known and when it was known about this danger.





Other Tire Aging Developments:



Ford Motor Company added a 6-year tire replacement recommendation, regardless of tread wear, to its website and all 2006 owner’s manuals. DaimlerChrysler acknowledged it too will add a 6-year replacement recommendation.



In response SRS has requested Ford, DaimlerChrysler, and the Alliance of Automobile Manufacturers support a NHTSA-issued Consumer Advisory in order to reach a wider audience.



SRS Letter to Ford

SRS Letter to DaimlerChrysler

SRS Letter to the Alliance