BRAKING SYSTEM

The inventions in this application concern a vehicle braking system and a method of actuating brakes in a vehicle braking system. The vehicle braking system (200) comprises a master cylinder (14) and first (20) and second (24) hydraulic braking circuits which include respective first (38a) and second (68b) wheel cylinders for braking first (22a) and second (26b) wheels. The master cylinder (14) has first (21a) and second (21b) outlets, first (140) and second (142) pistons associated with the first and second outlets (21a,21b), a fluid reservoir (16) and a master cylinder input member (10b) provided with a mechanical coupling to drive the first piston (140) and configured to drive the second piston (142) only through movement of hydraulic fluid. The second hydraulic braking circuit (24) is selectively disengageable from the master cylinder (14) via a separation valve (66). The second hydraulic braking circuit (24) includes a line (82,88) coupling a suction side of a pump (76) with the master cylinder reservoir (16). A pressure control valve (80) is configured to modulate the amount of fluid drawn from the reservoir (16) by the pump (76). The first invention is characterised in that the second hydraulic braking circuit (24) is coupled to the first outlet (21a) in fluid communication with the primary hydraulic chamber on the input member side (10b) of the master cylinder (14).