Abstract: In the case of a brake system for motor vehicles, having a brake pedal, a brake booster, a master brake cylinder and an electronically regulatable brake unit, which is arranged between the master brake cylinder and the wheel brakes and by which, via an electronic control unit, the brake pressure in the wheel brakes can be set independently of the preliminary pressure existing at the output of the master brake cylinder, when the brake booster fails, using the electronic control unit and the electronically regulatable brake unit, the brake pressure in the wheel brakes is generated such that a predetermined minimum desired deceleration course is obtained as a function of the pedal force applied by the driver by way of the brake pedal.

Abstract: A proportioning device for controlling the distribution of fluid from separate pressurizing chambers in a master cylinder to corresponding first and second wheel brakes of a vehicle. The proportioning device is adapted to respond to changes in the pressure from the separate pressurizing chambers to assure that the fluid pressure supplied to the individual wheel brakes is substantially equal at all times.