Tire revolutions refer to the number of complete rotations a tire makes while the vehicle is in motion. It is a measure of the distance covered by the tire. P255/45R21 tire completes 673 revolutions per mile or 417 revolutions per kilometer.
Tire revolutions are often used in various calculations related to vehicle dynamics, such as determining the distance traveled, estimating fuel consumption, or calculating the speed of the vehicle based on the rotation of the tires. Tire revolutions can also be tracked or monitored by certain vehicle systems, such as the anti-lock braking system (ABS) or the vehicle's onboard computer, for various purposes.