Braking system

A vehicle braking system comprising:

• a first hydraulic braking circuit including a first hydraulic wheel cylinder operable to brake a first wheel;
• a second hydraulic braking circuit including a second hydraulic wheel cylinder operable to brake a second wheel;
• a master cylinder having first and second outlets, first and second pistons associated with the first and second outlets, a fluid reservoir and a master cylinder input member provided with a mechanical coupling to drive the first piston and configured to drive the second piston only through movement of hydraulic fluid;
• and
• wherein the second hydraulic braking circuit is selectively disengageable from the master cylinder via a separation valve, the second hydraulic braking circuit including a line coupling a suction side of a pump with the master cylinder fluid reservoir, wherein a pressure control valve is operable to modulate the amount of fluid drawn from the master cylinder fluid reservoir by the pump,
• wherein the second hydraulic braking circuit is coupled to the first outlet of the master cylinder, and
• wherein the second hydraulic braking circuit has a first configuration in which an input force provided by a vehicle operator is applied to the first piston and carried through the first master cylinder outlet to apply a hydraulic braking force at the second hydraulic wheel cylinder, and has a second configuration in which the pump sends hydraulic fluid from the second hydraulic braking circuit directly into the master cylinder through the first outlet.