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How to tell if your tires are past their prime

Published July 19, 2012
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Tires are easily the most underrated safety feature of any vehicle. For the average passenger vehicle, the contact patch (the part of the tread that actually contacts the road) is roughly about the size of your open hand. Those four relatively tiny contact patches bear a lot of responsibility. They provide the entire grip required to stop, steer and accelerate your vehicle.

Most motorists neglect their tires and fail to realize the significant role they play in motoring safety. The most common fault is not ensuring tires are properly inflated. Many motorists will shop for a less expensive alternative to their OEM tires, sacrificing handling qualities for a few dollars. Too many drivers will settle for the compromise of an “all-season” tire for winter driving. On the other hand, a few auto enthusiasts will actually upgrade their tires to obtain improved handling characteristics and safety.

The bottom line is we should never take our tires for granted. Along with keeping them properly inflated, they should be frequently inspected for irregular wear patterns, punctures and tread life.

There is also another very important, but less obvious feature of your tires you should be paying heed to, their age.

Tire rubber compounds are subject to degradation as they age. Exposure to ozone and ultraviolet light will harden and dry the rubber, making it brittle. Signs of aging can be seen on the tire tread and sidewall in the likes of small cracks in the rubber. This is a visual warning to you that any tire with cracks showing in the sidewall or tread has reached the end of its service life and needs to be replaced.

Three significant problems arise with this aging. One, the tire rubber has hardened to the point where the level of grip is compromised. This will lengthen braking distances and reduce handling quality. Two, the rubber will become more porous, allowing air to leak out quicker increasing the chances of the tire developing dangerously low tire pressures. Three, with the aging of the rubber compounds, the tire stands a greater risk of delaminating or coming apart.

This obvious aging of the tires on your vehicle is relatively easy to assess. You should not expect more than five or six years out of a set of tires. Any tire older than this will eventually be subject to dangerous degradation and should be replaced. A visual inspection of your tires will reveal these telltale cracks in the tread or sidewall. Any tire exhibiting these traits should be replaced.

However there is also another danger that is less obvious. It too has to do with the age of the tire, but because these older tires have not been used their age is more difficult to ascertain.

In North America, there is no “Expiration Date” stamped onto new tires and they can sit around in a warehouse or tire store for years deteriorating from age with no visible indication. In Britain, the BRMA (British Rubber Manufacturers Association) “strongly recommends no tire should be used six years after it was made”. Some vehicle manufacturers such as Ford have lobbied the U.S. government to put a six-year expiry date on tires. The NHTSA has also acknowledged that tire age is a significant factor in safety.

There is a code on the tire that can tell you what the date of manufacture was. It is a four-digit number usually near the DOT stamp in an elongated oval that when deciphered will tell you the week and year of manufacture. For example, the code 3002 will tell you this tire was made in the 30th week of 2002. The number 0104 indicates a manufacture date of the first week of 2004. The tire in our photo has a code of 4010 and was built in the 40th week of 2010.

Your tires are a very important part of your vehicle safety. For your sake and that of your passengers, do a little research to be sure you are not compromising you safety when replacing your tires.

Here are some driving safety tips with regards to your vehicle’s tires:

Always use tires that suit your driving environment. Winter tires for winter conditions and summer tires or all season tires for May through to November in Southern Ontario.

Keep your tires properly inflated. Temperatures play a big role in tire pressures. As temperatures drop, so do tire pressures. Tires that are under inflated pose a safety risk and also decrease your vehicle’s fuel efficiency.

Have your vehicle’s wheel alignment checked. Winter pot holes can easily knock your vehicle’s wheels out of alignment which will increase tire wear dramatically and reduce fuel economy.

Don’t drive on tires that are more than seven years old. Age degrades tire performance and safety.

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