The hazards of old tires
QUESTION: I just saw a news story on TV that said many people are driving on old tires and they can be dangerous. I didn't get to a pencil and paper quick enough to write down the way to check the numbers on my tires. Can you please explain more about this?
ANSWER: Research indicates the likelihood of tire failure increases considerably after approximately six years of age. With the tread life of a modern tire lasting far longer than those of the past it's common to encounter tires that are beyond the six to ten year recommended lifespan. RVs, trailers and classic cars are especially likely to wear older tires as they are slow to rack up a lot of miles. One may also find a new tire that's actually several years old, still on the shelf, before being purchased. In the case of low production/exotic tires or those made overseas, it's not unusual to find a new tire that's already a year old.
While exposure to sunlight, ozone, and heat accelerate aging, even spare tires and those in storage seem to be similarly affected. Visible small cracks in the sidewall are an indicator of aging, although deterioration can occur internally and isn't readily detectable. Quite a few vehicle manufacturers recommend tire replacement at six years, regardless of remaining tread, and while some tire manufactures say 10 years is the maximum life one should expect, they play it safe and recommend you follow the vehicle manufacturer's recommendation (likely six years). A common recommendation is to have tires five years old or older inspected annually.
Here's how to read when a tire was made: Look for the tire identification code on the sidewall, containing between ten and twelve digits. It's usually found close to the tire/wheel intersection and is preceded by the abbreviation DOT. The code lists the manufacturing location, tire size, manufacturer's code, and the week and year the tire was manufactured. You may need to check both sides of the tire as the full DOT code containing the final three or four digits (date) may be branded only on one side. Tires made since 2000 use the final four digits to indicate the week and year it was built. For example 1505 means the 15th week of 2005.
The most important thing a vehicle owner can do to enhance safety and fuel economy is to regularly check and maintain correct tire inflation pressure. Low tire pressure wastes fuel, causes tire overheating and reduces wet weather traction. Tires should be checked when cold and one can find the recommended pressure on a sticker on the driver's door or door pillar. Don't use the maximum pressure found on the tire as this won't be appropriate for your particular vehicle. Also, buy your own gauge rather than trust the beat-up one on the end of the filling station hose.
When a tire requires repair due to a nail or screw puncture, insist on having the tire dismounted, inspected, and the puncture plugged and patched. A quickie and cheap plug insertion from the outside, while commonly done, is not an appropriate repair.
ABOUT THE WRITER
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at firstname.lastname@example.org; he cannot make personal replies.
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