MILEPOSTS Garage - The Online Classic Car Magazine Just because a tire looks new on the outside, doesn't mean it's safe. Don't take a chance on old tires!

Old tires can look like new on the outside and still be unsafe. (Image of triple band white sidewall tire shown.)
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Vol. 2, No. 12
February 13, 2004

Car Tires: Appearances Can Be Deceiving
by The Automotive Mileposts Staff

Image: MILEPOSTS Garage

You might think the actual miles on a tire are the most important indicator of how long they will last, but that isn't really true. Most of the tires manufactured today will simply wear out due to normal use, and since people are driving more miles these days, the life expectancy of a tire can seem to be quite short when judged strictly by the amount of time in service. A worn out tire under these circumstances is normally evidenced by tread wear indicators built-in to the tread during the manufacturing process. These tread wear indicator bands "interrupt" the normal tread pattern, and indicate the tire needs to be replaced.

But what about a tire that doesn't have any external signs to warn it may be near the end of its useful life? For instance, one that has very few miles on it, based on its deep tread and minimal wear, but it's not known exactly how old the tire is. The age of a tire also plays an important role as to how safe it is. This is especially true for tires mounted on classic cars and RVs. These vehicles normally see much less use, and while the tires on them may be 10 years old or more, they could have as little as 4,000 miles on them.

The average miles driven in the United States per person has increased from 8,685 in 1969 to 14,500 in 2001, and tire safety and durability has also increased greatly during this time. These statistics minimize tire failure due to age, since most tires are still relatively new when the tread wears out on them from normal use. But tires do not last forever. Nor do they always have warning signs that indicate they are past their useful life.

There are many factors that influence the average life expectancy of a tire, including exposure to sunlight and ozone, sitting for extended periods of time, and the amount of weight on them. Tires weren't designed to stand in one place for long periods of time, they were designed to roll around on a regular basis. Subjecting tires to long periods of standing can create flat spots, which prevent them from rolling smoothly, and cause them to build up too much heat. And too much heat spells trouble for a tire.

In fact, tires can age more quickly when they aren't used regularly, which is a real concern for classic car owners. Placing the car on jack stands when it won't be in use might help the tires somewhat, but could place strain on body and frame structures that weren't designed to support the weight of the car for extended periods.

If you're lucky, your tires will exhibit signs of aging that are easy to spot: cracks in the sidewalls, or a vibration in the steering wheel or a roughness at certain speeds, but don't count on it. The experts we spoke to said the average life expectancy of a tire on a classic car is just five to seven years. Much depends on how the car will be used. If the car is strictly a show car, and won't be driven other than for short distances to or from a car show, you might be tempted to push the longer limits of life expectancy. But if the car is going to be driven at highway speeds, or for any distance at all, it's best to play it safe and replace the tires more frequently.

All tires made in recent years are date coded by government order, which makes it easy to determine how old they are. The United States Department of Transportation now requires that every tire must have a four digit date code on the sidewall, indicating the date it was manufactured. Look for a string of numbers and letters that begins with "DOT" to see the date code. The code will look something like "0604" which indicates the tire was manufactured during the 6th week of 2004. This number only appears on one side of the tire, so you might have to crawl under the car to get the date.

Tires can be seriously deteriorated on the inside, while having a normal appearance on the outside. Finding out that a tire is bad at 70 miles per hour is not an acceptable risk. If you have a collector car, second car, or RV that sees little use, check to see how old the tires are. If you can't tell with any certainty, replace them, even if they look brand new on the outside.

Consider the many replacement tire options available for your vehicle as well. If your car isn't going to be judged, why continue to pay top dollar for Michelin steel belted radials just because that's what came on the car new? If the car isn't going to be driven much, you're not likely to need something with a high mileage guarantee or warranty. The tires will be old and past their safe useful life before the tread even comes close to wearing out. For this reason alone, we recommend buying less expensive tires, since you don't need tires capable of high mileage. You also won't be as likely to defer tire replacement to a later date due to the cost involved.

For the greatest safety and least cost, buy name brand tires from a reputable dealer. Make sure they're mounted and balanced properly when installed, have your front end alignment checked, always maintain proper air pressure, and check air pressure regularly.

Additional information: Car Tires 101: All You Ever Wanted to Know About Car Tires.

Copyright © 2004 Automotive Mileposts, Inc.
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