Abstract: A tandem master cylinder has a primary and secondary pistons disposed within cylinder bore formed in a cylinder housing, in tandem relationship. The secondary cylinder is formed with a longitudinally extending bore in which is disposed a pressure regulating valve. The pressure regulating valve has a variable set pressure which defines a split point with respect to the pressure applied to the front and rear wheel cylinders. The pressure regulating valve includes a member for varying the set pressure in response to damage to the hydraulic circuit of the front wheel cylinders for setting the split point higher than in the normal state.

Abstract: In a load sensing valve including a proportioning valve (P-valve) and a deceleration sensing valve (G-valve), a compensating device is installed for varying the volume of the fluid sealing chamber of the G-valve in accordance with the magnitude of sealed hydraulic pressure in the fluid sealing chamber when the sealed hydraulic pressure is lower than a predetermined valve to change the pressure controlling characteristic of the proportioning valve.