Abstract: A low vent pressure master cylinder reservoir cap diaphragm assembly is used to keep brake fluid in the reservoir but allow air to freely pass to and from atmosphere. The diaphragm assembly includes a flexible sealing component having an aperture and a fluid flow restrictive material bonded to the flexible sealing component covering the aperture. The fluid flow restrictive material allows a limited amount of brake fluid to pass through but allows air to freely pass through. The flexible sealing component is preferably made from a rubber material. The fluid flow restrictive material is preferably made from a material such as nylon that is either mesh or has small pores.

Abstract: A master cylinder provides separate flow paths through its secondary piston to provide greater fluid flow capacity from the reservoir to both the primary and secondary pressure chambers in response to the removal of brake fluid from the brake lines fed by the primary and secondary pressure chambers by a pump providing brake pressure for activation of one or more wheel brakes independently of the master cylinder. The secondary piston is provided with an axial fluid flow passage having check valves at each axial end permitting fluid flow only out of the axial fluid flow passage into the primary and secondary pressure chambers. A cross flow passage intersects the axial fluid flow passage between the primary and secondary check valves to communicate the axial fluid flow passage with the intermediate chamber and thus with the reservoir through the secondary compensation opening. The additional flow capacity to both pressure chambers provides improved reaction time for a traction control system at any wheel brake.