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Facts supporting the need for an awareness program
and additional
NHTSA study and rule making regarding tire “aging”
- From 1994 through 2004, NHTSA estimates that about 400 fatalities, annually, may be attributed to tire failures of all types … current data does not specify the number attributed to tire aging alone, but … NHTSA states “we do know that tire aging is a significant factor in tire related safety”. In a 2008 Consumer Advisory, NHTSA recommends that motorists should follow their vehicle and tire manufacturer’s recommendations concerning replacement of tires due to age. NHTSA goes on to state that “Old tires are also subject to greater stress, which increases the likelihood of catastrophic failure”.
- NHTSA has determined that thermo-oxidative degradation (“aging”) of tires is accelerated with higher temperatures and is a contributing factor for tire failures, such as tread separation.
- Traditionally, the end of service life of tires is independent of tire age and is defined as the point when the tread wears down to 2/32 inch . However, tires on some vehicles can be in service for many years and yet accumulate very few miles resulting in little or, in the case of full-size spare tires, no wear. NHTSA estimates that 50 percent of light trucks will still be in service after 14 years of age, and 25 percent after 20 years of age. This prompts concerns about the use of full-size spare tires in these vehicles as few owners replace their full-size spare when replacing the in-service tires.
- In testing actual “aged” tires, NHTSA has found that … “An evaluation of the tire and rubber material properties in different areas of the tires confirmed that the tire rubber compounds and the materials that bond them experienced thermo-oxidative degradation during service due to their heat and oxygen exposure over time as well as from service related fatigue. The tires experienced a reduction in peel (adhesion) strength between the steel belts, an increase in hardness of most rubber components, a loss of the rubber components’ ability to stretch, increased crack growth rates, and a reduction in cycles to failure in fatigue tests”.
- NHTSA’s field study showed structural degradation of tires in terms of internal cracks and separations resulting from the tires being used in service. This internal degradation and damage was nearly impossible to detect from a visual inspection alone.
- Vehicle manufacturers DaimlerChrysler, Ford, VW/Audi and BMW all recommend a maximum six year service life (from date of manufacture) for tires on their vehicles … including the spare.
- In a recent study conducted by North CarolinaStateUniversity, only 4% of those surveyed identified “aging” as a potential tire problem..
- Spare tires, tires in storage or on a shelf prior to use, or tires that are infrequently used on trailers or recreational vehicles, run the risk of premature aging and may be unsafe even though they may have sufficient amounts of tread or appear “new”.
- A study by Kalsher, Wogalter, Lim and Laughery (2005) suggested that a substantial percentage (26%) of people thought that tires could last 10 years or more. This indicates at the very least, some incomplete consumer knowledge about tire aging.
- In the N.C.State study, approximately half (44.9%) of the participants reported that they have not read the owner’s manual for the vehicle they drive. Of those who reported reading the owner’s manual, 63.7% reported that they have read less then 50% of the manual.
- According to NHTSA approximately 1% of vehicle fatalities are related to tire issues, while in the case of 15-passenger vans, approximately 11% of fatalities are related to tire issues.
- 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.
- Safety Research & Strategies, Inc has documented 159 incidents in which tires that were six years old or older experienced tread/belt separations. These incidents were the cause of 128 fatalities and 168 serious injuries. In a previous study at least a third of these type of incidents involved “aged” spare tires. In most cases these tires were put into service shortly before the accident.
- According to a 2008 survey of church and university 15-passenger vans in the KnoxvilleTN area, 40% of the vans surveyed had tires that were six or more years old … over 20% of the vans surveyed had tires that were ten or more years old. This is likely attributed to the relatively low annual use rate coupled with the belief, by most, that tire life is strictly a function of remaining tread depth.
- The accident that resulted in the death of Alexis James in July, 2007 was initiated by the failure (tread separation) of the left rear tire on a 1994 15-passenger van. The tire has been shown to be 13 years old and was unwittingly installed by a tire dealership/shop approximately one month prior to the accident. The accident report stated that from the remaining tire remnants, it appeared to be in like new condition. The tire was likely the original spare tire.
Prepared by:
Patrick James & Roderick Koehler – June, 2008
5013 Jade Pasture Lane
Knoxville, TN37918
Tel: 865-951-3544
E-mail:
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