Tire rotation is the changing of tire positioning on the vehicle in order to evenly distribute wear among all four tires.
Even for a well-aligned vehicle, tires will never wear at the same rate because of differing weight distribution and acceleration and brake forces. For example, on a front wheel drive vehicle, the front tires bear more weight, handle the steering, feel most of the braking, and pull the vehicle forward under acceleration. They might wear twice as fast (or even more) as the rear tires do if the tires are never rotated.
Even for a well-aligned vehicle, tires will never wear at the same rate because of differing weight distribution and acceleration and brake forces. For example, on a front wheel drive vehicle, the front tires bear more weight, handle the steering, feel most of the braking, and pull the vehicle forward under acceleration. They might wear twice as fast (or even more) as the rear tires do if the tires are never rotated.
Since all tires have a finite lifespan, and since lack of rotations allows aggresive tire wear, tires simply won’t last as long. On front wheel drive cars, it may also be observed that the front tires wear out, and then the rear tires have worn so slowly that they require replacement due to age rather than low tread depths.
Tires that are run for too long at the rear of a front wheel drive vehicle can be more prone to exhbitting cup-type wear, especially if they are not properly balanced, being run with weak shocks or struts or both. Certain vehicles and tire combinations may be prone to developing such wear even with good tire balance and healthy shocks or struts. There simply isn’t as much weight back there to help to prevent the tire from “skipping” (speaking loosely) against the road surface.
Rotation involves moving a wheel from one position on a vehicle to another. Unfortunately, it is very common for wheels (during rotations or otherwise) to be incorrectly installed. This can include over-tightening of lug nuts, uneven tightening of lug nuts, and not tending to corrosion on mounting surfaces. (For mounting surface corrosion, please see separate entry.)
A front wheel imbalance vibration is more likely to be noticed than a rear wheel vibration. If tire balance is not checked in combination with a tire rotation, there is a risk that the driver will experience a vibration after the rotation that they did not experience before. While some vibrations might show immediately, others may not be obvious until the vehicle is driven at higher speeds.
While it is advisable to rotate at steady intervals, this does not mean that rotations should always be done at rigid mileage intervals. For example, if a front wheel drive vehicle has two worn tires up front and two fresh tires at the rear, the tires should not be rotated, even if a wooden reading of the maintenance schedule “says” that they should be. In this case, putting the worn tires at the rear of the vehicle would increase the risk of loss of control. Or, to give another example, if one tire has recently been replaced on a front wheel drive vehicle, and it’s been installed at the front, and it only slightly exceeds the tread depth of the rear tires? It should stay put. It can be rotated later once it’s worn down slightly below the tread depth of the rear tires. To do otherwise would be a waste of money.