Hub cap for a vehicle axle

The hubcap has an electric, magnetic or optical device (10) to detect the hub revolutions, consisting of a transmitter (17) and a receiver (18) fitted in the hubcap and rotating with it. It also has an electronic calculating unit (11) to transform the revolutions detected by the device into the display value. The hubcap has provision for a clamping device (13) for the calculating unit and the indicator (12).