DETROIT, MICH. — The Ford Motor Co., in a move stirring the
tire industry, has started urging consumers to replace
tires after six years. The car maker said its research
shows that tires "degrade over time, even when they are not
being used." That means even pristine-looking spares that
have never left the trunk should be discarded after a half-
That's a radical concept in the staid U.S. tire business,
which insists there's no scientific evidence to support
a "use by" date for tires. It would also surprise most
motorists, who are taught that a tire's life span is
measured mainly by tread depth. The tire industry said that
tires are safe as long as the tread depth is a minimum of
1/16th of an inch, no matter what the age, and there are no
visible cuts, signs of uneven wear, bulges or excessive
cracking. Other trouble signs are if tires create vibration
or excessive noise.
"Tires are not milk," said Daniel Zielinski, a spokesman
for the Rubber Manufacturers Association, the tire
industry's main trade group.
For many consumers, the issue never comes up, since
passenger-car tires last an average of 44,000 miles,
meaning they are usually replaced before hitting the six-
year mark. But many people simply assume that unused spare
tires, even those that are a decade old, are as durable as
brand-new tires, and sometimes use those spares as full-
time replacements for the regular tires. Classic-car buffs
and others who drive only infrequently could also be
affected by the latest research.
In its new stance on tire safety, Ford is getting some
support from other researchers. Sean Kane, president of
Safety Research & Strategies Inc., an auto-safety research
firm working with lawyers who are preparing lawsuits
arising from accidents thought to be linked to aging tires,
said older tires are a road hazard. Kane's group has
collected a list of 70 accidents involving older tires,
which resulted in 52 deaths and 50 serious injuries.
In a sense, the U.S. car industry is just catching up to
global standards. Many European automakers as well as
Japan's Toyota Motor Corp. have long warned drivers,
including those who buy their cars in the U.S., that tires
are perishable. Many of them also use a six-year threshold
for the age of a tire.
DaimlerChrysler AG has already adopted a position parallel
to Ford. The automaker's Mercedes division had been telling
drivers that tires last only six years.
But starting last fall, the Chrysler group began including
such a warning in 2005 owner's manuals. "We did do some
research and we found that's just a pretty safe and steady
guideline," said Curtrise Garner, a Chrysler spokeswoman,
adding that "it's a recommendation, not a must-do."
Ford's new stance on tire aging is a direct outgrowth of
the Firestone tire recall that began in August 2000. That
episode involved Firestone tires failing suddenly, mostly
on Ford Explorers, leading to a wave of deadly crashes. The
crashes sparked a series of lawsuits, including monetary
and personal-injury claims, some of which are pending.
Ford's new position won't affect those lawsuits. But it
could play a role in future legal action. Some attorneys
who have sued over the Firestone case are now mounting
cases that focus on tire age.
John Baldwin, a Ford materials scientist who studied the
root cause of the Firestone problems and has spearheaded
the automaker's continuing research on tire aging, said
Ford's intention is to develop a test to help prevent
another Firestone-type debacle. He said Ford's research
into the Firestone problem showed that as tires age, the
chemistry of the rubber changes as oxygen migrates through
the carcass of the tire. This leads to a weakening of the
internal structure that can result in tire failures.
Driving in hot climates or frequent heavy loading of
vehicles speeds this aging process, he said.
Firestone spokeswoman Christine Karbowiak said the company
can't comment on Ford's new recommendation because it
hasn't seen Ford's research.
Tire makers certainly don't want to see the six-year rule
become any more deeply ingrained. While it might seem that
putting a limit on the life span of tires would be a boon
to tire makers, who would presumably sell more tires, the
costs and complications it could create are considerable.
Among other things, the industry is worried about the
logistical problems that would arise if customers suddenly
started demanding only the "freshest" tires. In some cases,
tires take months to move through distribution channels
from factories, through wholesalers, and then on to retail
HOW TO FIND A TIRE'S AGE:
* Look for the letters DOT on the sidewall (indicating
compliance with applicable safety standards set by the U.S.
Department of Transportation).
* Next to these letters is the tire's serial number, which
is a combination of up to 12 numbers and letters.
* The last characters are numbers that identify the week
and year of manufacture. For example, 1504 means the
fifteenth week of the year 2004.
* The numbers are printed on only one side of the tire,
which sometimes is the side facing inward.