How do car speedometers work?


I know that airplanes use pitot tubes which work with airflow, but since cars don’t have them (or at least I highly doubt they do), how can they still precisely measure speed?

In: Engineering

They measure how fast the wheel(s) turn, since the faster a wheel turns the faster you will move.

This is also why your speedometer won’t be correct if you change the rim size of your wheels unless you have it recalibrated.

Wheel speed sensor in each wheel hub sends an electronic signal which averages then displays on your speedometer

Wheel speed (ABS) sensor measure wheel speed as mentioned before. But thats not always the case. Many cars also use geared/-less electronic speed sensor directly on the differential or transmission/gearbox output shaft, or on even older cars – all way mechanical with steel cable.