Mechanical control device for a disc brake

A mechanical control device for effecting operation of a friction member belonging to a brake mechanism, comprising a housing in which a bore slidably receives a piston adapted to be associated with the friction member, two members extensible along the axis of the bore, and a control member which is connected to a first one of the extensible members and of which rotation in the direction corresponding to operation of the brake mechanism causes the second extensible member to extend from the first member, so urging the piston in the direction corresponding to operation of the friction member, adjusting means being provided to take up wear on the friction member, characterized in that the adjusting means comprise an element normally connected to the first extensible member by one-way transmission means enabling said element to turn relative to the first extensible member through an angle corresponding to the wear on the friction member beyond a predetermined value upon operation of the control member, resilient coupling means then coupling the second extensible member and the piston, but enabling said element to cause the second extensible member to turn through said angle so that it extends from the first extensible member upon return of the control member to its idle position.