WASHINGTON -- Ford Motor Co. has started recommending that tires be replaced after six years of normal use because they degrade over time. DaimlerChrysler AG is about to do the same.
Tire industry representatives insist there are too many variables in tire life to set a hard-and-fast expiration date. They say storage and maintenance have more to do with a tire's degradation than chronological age.
On its Web site and in its owner manuals, Ford now states: "Tires degrade over time, even when they are not being used. It is recommended that tires generally be replaced after six years of normal service." A Ford spokesman says the company based its decision on its research in tire aging.
DaimlerChrysler will add the same advice to owners' manuals in the 2006 model year, a spokeswoman says.