Abstract: A brake circuit has a brake connected with a master cylinder via a brake application line. The brake master cylinder has a first chamber in which brake fluid is pressurized on movement of a first piston in a brake applying direction by an operating device. The first chamber is connected via a first port and a non-return valve with the brake application line of the circuit. A second chamber is in communication with the brake return line of the circuit via a second port and has a second piston moveable by the brake operating device in brake applying and releasing directions. The second chamber is also in communication with a reservoir via a third port when the second piston is in a fully released position.