Abstract: A master cylinder includes a primary piston and a secondary piston, each formed with piston ports which include two different kinds of ports, i.e. first ports for ensuring communication between a reservoir and a pressure chamber of the master cylinder, and second ports through which brake fluid is sucked from the reservoir during automatic break control. The second ports are greater in number than the first ports and are positioned forwardly of the first ports so that the second ports are closed by primary cups which are provided on the inner wall of the cylinder body so as to be in sliding contact with the respective pistons before the first ports when the respective pistons are advanced. An annular wall having a greater inner diameter than the outer diameter of the pistons is formed on the inner wall of the cylinder body to support the back of each of the primary cups. An annular groove is formed in each piston so as to communicate with the first ports.

Abstract: A master cylinder includes a primary piston and a secondary piston, each formed with piston ports which include two different kinds of ports, i.e. first ports for ensuring communication between a reservoir and a pressure chamber of the master cylinder, and second ports through which brake fluid is sucked from the reservoir during automatic break control. The second ports are greater in number than the first ports and are positioned forwardly of the first ports so that the second ports are closed by primary cups which are provided on the inner wall of the cylinder body so as to be in sliding contact with the respective pistons before the first ports when the respective pistons are advanced. An annular wall having a greater inner diameter than the outer diameter of the pistons is formed on the inner wall of the cylinder body to support the back of each of the primary cups. An annular groove is formed in each piston so as to communicate with the first ports.

Abstract: In a disc brake assembly including a caliper member mounted on a vehicle body structure in such a manner as to straddle a portion of a rotary brake disc secured for a road wheel, a friction pad supported on the caliper member by means of a pair of hanger pins to be moved toward and away from one side surface of the brake disc for engagement therewith and disengagement therefrom, the friction pad having a backing plate secured thereto to be engaged at one side end face thereof with a torque receiving portion of the caliper member in braking operation and a fluid actuator mounted within the caliper member to press the friction pad against the one side surface of the brake disc, a side projection is provided on at least an upper or lower portion of the one side end face of the backing plate for engagement with the torque receiving portion of the caliper member or on at least an upper or lower portion of the torque receiving portion of the caliper member for engagement with the one side face of said backing plate