an instrument on an automobile or other vehicle for indicating the rate of travel in miles or kilometers per hour.

Why is speedometer higher than actual speed?

For example, if you put new tyres on your car, the diameter will increase (more tread, which wears down over thousands of miles) or increase the tyre pressure. This means that, for each tyre rotation, your car travels further, meaning your speed is greater.

How does speedometer indicate?

Speedometer, instrument that indicates the speed of a vehicle, usually combined with a device known as an odometer that records the distance traveled.