From NHTSA:
Tire Aging
•• Any rubber begins to break down
over time. Heat accelerates this process.
The rubber in your tires also breaks
down over time, a process referred to
as tire aging.
•• Even though a tire may have a lot of
remaining tread, its integrity may be
compromised. The effect of aging may
not be visibly detectable.
•• Tires age whether they are driven on or
not and are a concern for infrequently
used vehicles and spare tires.
•• An analysis of crashes in the National
Automotive Sampling System from
2005-2007 estimates that 90 people die
and an additional 3,200 are injured each
year in crashes in which tire aging was a
factor (
www.scribd.com/doc/137377038/
NHTSA-Report-on-tire-aging).
•• As tires age, they are more prone to
failure.
•• Some tire manufacturers recommend
replacing tires that are 6 to 10 years old,
regardless of tread wear.