Master cylinder having a hydraulical reactiondevice and brake system having such a master cylinder

The cylinder has a braking assisting device retransmitting characteristic action of a braking level to a control rod, and including an actuating piston (6) mounted in a primary piston (5). The device has a connecting piston (36), in the form of bush, tightly mounted around a part of the piston (6) and in a bore of the piston (5). A backlash spring permits to create backlash in the beginning of a braking phase. The piston`s (5) annular face (34) permits to block the force of hydraulic actuating pistons on a distributor-plunger. A return spring (50) defines a part of changing threshold of control ratio. An independent claim is also included for a braking assembly including a master cylinder and a pneumatic braking assistance servomotor.