A brake system particularly for electric vehicles which provides power assisted hydraulic brakes in which the degree of power assistance is regulated for the braking force desired by the use of an operator compressible carbon pile in the circuit of an electric motor which drives a pump to vary the pressure in a master cylinder. In the event of any breakdown or malfunction for any reason in the power assist portion of the system the carbon pile may function as a compressible mechanical link between the hydraulic brakes and the foot pedal for manually applying the brake.