The practice of periodically moving the wheels and tires of an automobile from one position to another on the same vehicle in order to ensure that all of the vehicle’s tires receive approximately the same amount of wear over time; i.e. that no particular tire wears out more quickly than any other. This is a consequence of the fact that a tire’s lifespan is often strongly biased by its particular position on the vehicle (e.g. front or rear, driver’s side or passenger side) because the masses supported by and the forces applied to different parts of the vehicle are often uneven; for example, in front-engine vehicles, the front axle typically supports a much greater load than the rear axle, meaning the tires on its wheels experience different forces that may cause their tread to wear out faster than the tread on the rear tires.