The ABS brake system has the master brake cylinder (10) connected to each wheel brake by a main duct (P1) with a control valve and a second duct (P2) with a second control valve. The main duct has a direct connection the master cylinder while the second duct includes a flow restriction (O). A third control valve isolates the wheel brake from the hydraulic supply and connects it to the recirculating pump. In the ABS mode the flow restriction isolates the separate brakes from fluctuations in the hydraulic supply. The solenoid valves are linked to a control which links the valve action eg. the first valve is open when the second valve is shut, and vice versa. The fluid recirculation pump is electrically driven. The system effectively isolates the separate brake circuits from pressure fluctuations in the hydraulic system.
