Armed with the knowledge of your tire life expectancy, tire wear patterns and tire aging, you can best determine how much money to invest when buying new tires and how to determine when they need to be replaced. It is impossible to predict just how long any specific tire will last. However there are several warning signs and indicators that assist you in determining when they become unsafe to drive.
Tire Ratings
To understand how your tires age and wear you must understand how they deteriorate. Tires are compressed rubber and have three different ratings for how they wear, temperature, tread wear and traction.
Temperature ratings are given to tires and will be an "A", "B" or "C" rating. "C" rated tires are the minimum allowable for passenger vehicles. Each rating corresponds to a temperature at which the tire dissipates heat under a given amount of loading. A "C" rated tire will fail at a lower temperature than an "A" rated tire. This is especially true if a vehicle is heavily loaded.
Tread wear ratings are a three-digit number that gives you some idea as to the expected life of your tire. A rating of 100 is a baseline number, meaning it should last about as long as a normal tire, whereas a tired rated with a 150 is expected to last about one and half times longer than a tire with a rating of 100.
Traction ratings begin with "AA" and go to "A", "B", and then "C", which is the lowest traction rating a tire can have. These ratings represent your tires ability to work in less than ideal conditions, such as wet roads, and how long it takes them to stop. "C" rated tires are marginal where as "AA" rated tires are the best.
When shopping for tires it important that you never buy a tire that has less of a rating then is recommended for your vehicle.
How Long Will They Last?
Understanding how your tires are rated is just a start, but how can you know precisely how long they will last? Typically a driver of a car, or light truck, can expect their tires to last anywhere from 30,000 to 80,000 miles, depending on the manufacturer, the driver, the amount driven, the road conditions and the heat. As you can see, several variables factor into tire life, making any accurate predictions nearly impossible.
When Should I Replace My Tires?
The first indicator as to when you should replace your tires is the tread wear bar. A tread wear bar is a small bar that spans the distance between your treads. When the bar becomes exposed, or is even with the tread it is time to replace your tires. If your tires don't have tread wear bars you can check the depth with a coin, such as a penny. Tread depth of less than the head of Abe Lincoln on a penny indicates it is time to replace your tires.
Other factors to consider are uneven wear on one side, meaning your tires need to be rotated and your alignment and shocks should be checked. Uneven wear can also cause significant problems if your tires wear down far enough. Tires do not wear evenly, which is why you need to rotate them on a regular basis. Over or under inflation can also cause your tires to wear more than they should.
Extending Tire Life
In order to extend the life of your tires you should rotate them every 4,000 to 10,000 miles, depending on the manufacturer of the car and the tire. Consult your vehicle service manual to get an idea as to when you should rotate your tires. Since your front and rear tires wear at different rates it this is important to extend the life of your tires. Check your tire pressure regularly and make sure they are inflated to the recommended PSI. This will increase their life, your MPG and your safety.
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