The Life of Car Tires

The useful life of automobile tires is an often-debated topic that doesn't have a concise, perfect answer. The process of making typical radial tires involves bonding a rubber compound to steel cords and fabric plies, which gives tires their strength. During the manufacturing process, anti-aging ingredients are added to the rubber, but that doesn't mean that a tire will last until all of the tread is gone. There are many factors that affect how long a tire lasts, from how soft the tire's compound is to how the tire is used.

How many miles do tires last?

As recently as the 1970s, tires had a relatively short life span of less than 20,000 miles, or about two years. By 2000, harder compound tires were being made that could last for 60,000 miles over four or more years of constant use. Currently, there are some tires that can get as many as 80,000 miles of treadwear. Treadwear ratings are listed on tires and can range from 60 to more than 500. An example would be a treadwear grade of 400, which would last twice as long as a tire that has a 200 grade. The tire's load rating is listed on the tires as well. The larger the number, the higher the load capacity; for example, an "89" load rating is 1,279 lbs. and an "85" rating is 1,135 lbs.

Tire Age Consideration

Although tires have a tread wear rating that can be measured in miles, another important factor to take into account the calendar age of the tire. Tire makers and the U.S. National Highway Traffic Safety Administration (NHTSA) are currently studying the effects on tires from exposure to the sun, type and regularity of use, and how well they are maintained. The British Rubber Manufacturers Association (BRMA) recommends that tires that have not been put into use should not be used more than six years from when they were made. All tires should not be used for more than 10 years. In 2005, The Japan Automobile Tire Manufacturers Association (JATMA) recommended that tires be inspected after five years. If tires are 10 years old or older, they should be replaced. Many European car manufacturers and some U.S. car companies say that tires should never be used for more than six years.

Tire compounds

Tires come in a wide variety of compounds, from very soft to very hard. High performance sports cars such as a Porsche 911 or a Corvette are generally going to come with high-performance compound tires that grip the road better due to their softness. Those tires do not last as long as tires made from harder compounds. Normal street cars like a Toyota Prius come with harder tires that last longer. Tires for different vehicles also have different speed ratings that range from Q (up to 99 mph) up to Y (189 mph).

Driving styles

Another factor that affects how long a tire lasts is the type of driving they are subjected to. If you are an aggressive driver who frequently corners, brakes and accelerates near the car's limits, the tires won't last as long as the same tires on a car that is driven more conservatively.

Air pressures

It is crucial for a tire to have the proper air pressure at all times. Not only does that promote better fuel economy, but it can extend the life of the tire by as much 50 percent. Under-inflated tires can exhibit cupping, in which they wear unevenly on the edges of the tread and can cause excess noise and vibrations. Over-inflation can cause tires to wear unevenly in the center of the tread. Improper tire inflation also can result in damage to the tires, wheels, and other car components when hitting potholes, rough road, or objects in the road. Even when driving on clear roads in good condition, keeping the tires properly inflated ensures that there is less stress put on them and that they don't get as hot, which can cause the rubber compound to break down.

Tire Rotation and road conditions

Regular rotation every 3,000 to 5,000 miles is an important way to promote tire longevity. Tires on the drive axles wear faster, especially for drivers who are given to abrupt starts and stops. For front-wheel-drive cars, the rear tires are moved the opposite sides of the front, and the more worn front tires are moved straight back. Rear-wheel-drive vehicles should be rotated in the opposite way, with the fronts going to the rear opposite sides and the rears moving to the front on the same side. To ensure proper rotation, follow the manufacturers recommendations.

Another factor in tire wear is the road conditions. For example, driving frequently on gravel roads or very rough roads will cause more wear than if the car is driven predominantly on smooth asphalt.

References

• The Tire Rack