Abstract: The unit has a rotating hub (10) having an outwardly projecting radial flange (11) defining an outwardly facing edge (12), and a braking rotor (20) which is integral with or fixed for rotation with a flange (21, 41) which projects radially inwards and which defines an opening (23, 43) with an internal edge (22, 42). The edges (12 and 22, 42) of the two flanges (11 and 21, 41) are adjacent to each other and face each other radially. The two edges (12 and 22, 42) have, at least along one portion thereof, the same noncircular shape, for example an oval or lobe shape, in the same radial plane in order to enable the braking torque to be transmitted from the braking rotor (20) to the hub (10). The braking rotor may be mounted on the hub flange (11) by way of an annular support member (40).