Abstract: This device, which is intended to brake a wheel of a vehicle rotated by a ive shaft carrying at its free end an epicyclic train reducer housed in a casing, is characterized in that it is fixed on the outer face of the bottom of the casing and comprises a watertight case enclosing at least one friction disc interlocked in rotation with the sun wheel of the reducer, as well as an annular plate for moving the disc axially and applying it against at least one internal friction surface, this plate being itself axially movable towards the disc under the action of control means situated inside the casing.