On Wed, 15 Jun 2005 23:54:22 -0400, MoPar Man > wrote:

>Tires get an expiration date
>Tuesday, May 31, 2005
>By Timothy Aeppel, The Wall Street Journal
>http://www.post-gazette.com/pg/05151/513329.stm
>
>---
Tires DO deteriorate with age - and there are many factors that
contribute.
Filling the tires with nitrogen instead of atmospheric air extends the
life of tires considerably, because atmospheric air is about 21%
Oxygen. The oxygen oxidizes components of the rubber - notably the
plasticizers, from the inside out. The oxygen (in the air) migrates
though the inner liner, around the cords, and eventually to the
atmosphere by osmosis.
Keeping tires out of direct sun and heat also helps - as both
UltraViolet and Ozone also deteriorate rubber.

Just about any tire I have had for more than 4 or 5 years, regardless
of mileage and tread-depth has lost significant wet traction, and also
start squealing on warm pavement. I threw away a 4 year old set of
TigerPaw Touring tires last fall with 3/4 tread on them so I would not
be tempted, in a moment of weakness, to put them back on the van when
the snows came off this spring.
Those tires wore like iron - and had about the same amount of
traction. When new, they were pretty good, but by 4 years, they were
definitely getting dangerous.

--------
>
>Main points:
>
>Drivers are being advised to start paying attention to the age of
>their tires.
>
>Ford has begun urging drivers to replace tires after six years,
>regardless of wear.
>
>The tire industry says it's more important to monitor tread depth than
>age and recommends that treads be at least 1/16 of an inch thick.
>
>Some European car makers as well as Japan's Toyota Motor Corp. have
>long warned drivers that tires are perishable.
>
>-----------
>
>Drivers who know to check tires for worn treads and low air pressure
>now have something else to worry about: vintage.
>
>Ford Motor Co., in a move roiling the tire industry, has started
>urging consumers to replace tires after six years. The car maker says
>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 pitched after a half-dozen years.
>
>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 lifespan is measured mainly by tread depth. The tire industry
>says 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," says 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, says older tires are a road hazard. Mr. 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 car makers 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 car maker'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,"
>says Curtrise Garner, a Chrysler spokeswoman, adding that "it's a
>recommendation, not a must-do."
>
>Other car makers are also taking up this question, and some are
>reaching a different conclusion than Ford. General Motors Corp.
>spokesman Alan Adler says GM has discussed the aging issue, but
>doesn't have any research that supports a move to such a guideline.
>"We're not joining in the six-years-is-the-magic-number thing right
>now," he says.
>
>The age of tires already appears on tires, but as part of a lengthy
>code that is difficult for average consumers to decipher. To find the
>age of a tire, look for the letters DOT on the sidewall (indicating
>compliance with applicable safety standards set by the U.S. Department
>of Transportation). Adjacent 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.
>
>Not only are the numbers difficult to interpret, but they can be hard
>to locate: The numbers are printed on only one side of the tire, which
>sometimes is the one facing inward when the tire is mounted on a
>wheel.
>
>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 car maker's continuing
>research on tire aging, says Ford's intention is to develop a test to
>help prevent another Firestone-type debacle. He says 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 says.
>
>In April, Ford posted a warning on its Web site saying that "tires
>generally should be replaced after six years of normal service." The
>company also plans to include similar wording in owner's manuals
>starting with the 2006 model year.
>
>Firestone spokeswoman Christine Karbowiak says 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
>lifespan 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 outlets.
>
>"We don't have any data to support an expiration date (for tires),"
>says Mr. Zielinski of the RMA. He agrees that age can be a factor in
>tire performance, but says it shouldn't be used as the sole reason to
>determine that a tire is no longer usable.
>
>Mr. Zielinski says Ford went public with its position without sharing
>its research with the tire association or individual tire makers.
>Ford, in turn, says that it presented its research in trade
>publications and at a series of public forums, including a technical
>meeting of the rubber division of the American Chemical Society in San
>Antonio, Texas, two weeks ago. Ford has also given its research to the
>National Highway Traffic Safety Administration, which is developing a
>test to simulate the effects of aging on tires.
>
>Ford's test involves putting inflated tires into an oven for weeks at
>a time. The tires are then taken out and studied to see, among other
>things, how well the layers of rubber hold together.
>
>Strategic Research wants tires to be labeled more clearly with the
>date they were produced, so consumers can better identify older tires
>and, ultimately, an explicit expiration date.