Automotive hydraulic pressure brake system

Automotive hydraulic pressure brake system with a stroke simulator is proposed which while the electric control system is functioning properly, the supply of hydraulic pressure from a master cylinder is cut off and hydraulic pressure is generated by a power pump. This improves response upon rapid pressure increase while minimizing the increase of pedal stroke and the worsening of the pedal feeling. A bypass is provided to communicate the master cylinder to the wheel cylinders while bypassing an on-off valve to be closed during ordinary braking. A shut-off valve is provided in the bypass and a check valve or a relief valve for allowing only a fluid flow from the master cylinder toward the wheel brake cylinders is provided.