Wheel cylinder

A wheel cylinder for a drum brake, said cylinder comprising a body provided with a longitudinal bore, two pistons sliding outwardly in opposite directions in said bore under the action of pressure from a pressurized fluid introduced between said pistons and against the force of at least one return spring of shoes of said brake, and means limiting return travel of said pistons when said pressure is released, said means limiting the return travel consisting of two assemblies each of which comprises a resilient ring having friction means disposed at an outer periphery thereof, and each assembly being disposed, respectively, in an annular groove located in the respective pistons so as to provide a specific axial clearance between a radial wall of the respective annular groove and an adjacent side of the respective assembly, wherein each resilient ring is an open retainer ring of variable thickness about its perimeter so as to effect a substantially uniform pressure over its outer periphery against the inner surface of said cylinder and each respective friction means has a substantially constant coefficient of friction, said assemblies being provided in order to resist said return spring and to yield under retraction forces created by the drum brake.