Tire Rotation 101
Equalize tire wear and maximize tire life
Most people judge their vehicles' tires by a common sense set of parameters: Will they be safe from blowouts and tread separations? Will they be rugged enough to deal with potholes and other road hazards? Will they have sufficient traction in rain or snow? And the easiest to measure: Will they last long enough so I don't have to shell out a bunch of money for new ones before a reasonable amount of time?If you burn rubber, you're burning money.
You can do several things to increase your vehicle's tire-life. Most important is driving habits; if you burn rubber, you're burning money. Proper inflation is important. And another way to really help extend the life of your tires is a well-thought plan of regular tire rotation.
Rotation means you are changing where the individual tires are mounted on the vehicle. Let's assume you have a front-drive car with all four tires the same size. Each tire will carry a different load and be faced with different situations. The front tires will carry over 60 percent of the car's weight. They are also responsible for putting the power of the engine to the road, and for all the steering. Finally, they are responsible for about 80 percent of the braking.
It stands to reason, then, that the front tires will wear much more quickly than the rears. Not only that, but the right front tire might tend to wear out more quickly than the left front because the nature of American traffic means that left-hand turns (which load the right-front tire) tend to be taken at higher speeds, and under higher loads, than right-hand turns (which load the left-front tire). And, right-side tires are more likely to be faced with road hazards and hitting curbs. The result of all this is tires wearing out at different rates.
To make the entire set wear at the same rate, that is, to equalize tire wear and thus maximize tire life, you can rotate them. With some vehicles, the owner's manual will have a recommended tire rotation schedule and a diagram of the rotation. A typical schedule may call for rotation every 5,000 miles with a pattern that's sometimes called "cross-rotation." For example, the front tires will be moved to the opposite sides of the rear, right-front to left-rear and left-front to right-rear, and the rears moved straight forward. If you follow this through, you will see that, eventually, every tire will have been to every spot on the car, and then it starts all over again.
There are a couple of points to remember about rotation. First, while it's easy and quick to use an air-powered impact wrench to take the wheels off, the wheel nuts or bolts should not be tightened with the impact wrench because they'll be too tight. Some night you may have a flat tire and have to remove the nuts that somebody else hammered on with an impact wrench. Instead, the nuts or bolts should be tightened with a torque wrench to the manufacturer's recommended setting. If you don't know the correct setting, any reputable tire shop should be able to help.
Second, many manufacturers recommend what are called "differential tire pressures," in which the fronts and rears are inflated to different pressures. Since different tires carry different loads, this only makes sense. But when you rotate the tires, you'll have to re-set the tire pressures to make them correct.
And here's one tip for setting tire pressures. Do it when the tires are at ambient temperature, and in the cooler part of the day; early morning is a good idea. Once the day warms up, the pressures will increase as the air in the tires gets hotter. In the summer, for example, as the sun comes up and warms the tires on one side of the car, they can easily gain two or more psi over the ones on the other side, still in the shade. And if you set the pressures when everything is already hot, then when things cool back down the tires will be way underinflated—and that's dangerous.
So, apply common sense, pay attention to the rotation schedule, tighten the nuts or bolts with a torque wrench, get yourself a good tire pressure gauge and use it, and those tires will pay you back with the longest life possible.
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