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Advice & More November 2016

Tires Grow Old Too!

By Bill Siuru

Heavily loaded tires stored outdoors in sunny, hot climates and only driven occasionally see the most severe service conditions and potentially have the shortest calendar lifespan. Motorhomes are a good example. Lightly loaded tires on vehicles parked in garages and driven daily in moderate climates can have the longest life.

Most seniors don't drive their vehicles anywhere as much as when younger, maybe only a few thousand miles a year or less. They also keep their vehicles longer, sometimes for decades. This means mechanical parts like engines, transmissions, brakes, etc. see minimal wear but this is not the case for tires that have limited life.

Tires can degrade over time because of chemical reaction within the rubber components, cyclic fatigue, neglected maintenance and road hazards. Cracks in the sidewalls and inside the tire can develop over time which can eventually result in the steel belts separating from the rest of the tire. While anti-ozinant chemical compounds added to rubber can slow aging, nothing totally stops the effects of time on tire life.

There is no consensus among automakers, tire manufacturers and even the National Highway Safety Traffic Administration (NHTSA) as to the lifespan of a tire. Best estimates range from six to ten years. Since the typical motorist drives about 12,000-15,000 miles annually, tires will have to be replaced in three to four years, long before aging takes its toll. However, if you only drive a couple of thousand miles yearly, this time could be 10 to 15 years, and becomes a problem.

There are many factors that affect life. Heavily loaded tires stored outdoors in sunny, hot climates and only driven occasionally see the most severe service conditions and potentially have the shortest calendar lifespan. Motorhomes are a good example. Lightly loaded tires on vehicles parked in garages and driven daily in moderate climates can have the longest life.

Those living in California or Florida should be especially concerned because research shows that tires age more rapidly in warmer climates especially when exposed to sunlight. Coastal climates can also increase the aging process. Since the NHSTA has found higher-speed rated tires lose the least capability with increasing age, you might consider buying them than those that originally came on your vehicle if you live in a hot climate.

Other factors include maintenance, or actually lack of it. Proper inflation and proper wheel alignment is very important and regular cleaning to remove road grime and brake dust can help. Punctures, cuts, hitting potholes and curbs and other road hazards reduce useful life.

You can determine the age of a tire by the DOT four-digit number on the sidewall amongst the many letters and numbers here. Referring to the picture, the first two numbers represents the week in which the tire was made. The second two represent the year. For example, the DOT Code 5107 mean the tire was made in the 51st week of 2007. Incidentally, this tire is pretty near the end of its life, even if there is still plenty of tread left. Since this coding system has been in use since 2000, if you find a different DOT code, the tire is probably only good for a tree swing.

Sometimes the DOT code is on the inner sidewall so you might have to jack up the vehicle to see it. However. the NHTSA now requires all the information numbers, including date of manufacture, be on both sides of the tire.

When checking the age of a tire, also visually check its condition. Look for any signs of aging like tread distortion and small and large cracks in the sidewall. If you experience vibration while driving, it could be a sign of tire aging.

Don't forget the spare. If you have a full size spare, include it when rotating tires. Not only will this prevent the spare tire from sitting idle, it will extend the time before tires have to be replaced. A spare tire sitting in a hot trunk can actually age faster even though it is never used. Spares mounted under a truck or SUV are exposed to dirt and other hazards that can decrease life.

When buying new tires, check to make sure that they don't have a reduced life because they sat in the warehouse for a few years. A tire on a store shelve will age, maybe just a bit slower. Especially look for date on tires for limited production vehicles that are only manufactured periodically, that may be years apart. Also check dates on tires being sold at a deep discount. The manufacturer or dealer might be trying to clear out their inventory of old or discontinued tires. These are probably okay for high-mileage use, but not for vehicles that aren't driven much.

 

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