locking washer 82 that is received within a groove 83 of the outer housing 65 to hold the components in their assembled condition the spring 79 also exerts a restoring force on the elements of the adjusting mechanism 34 when the brake is deactuated to hydraulically actuate the brake assembly 11 fluid pressure is introduced into the cylinder bore 21 via the passage 27 the fluid pressure will cause the piston 23 to slide axially in the bore 21 and bring the associated brake pad into engagement with the rotor braking surface 15 simultaneously a reactive force will be exerted on the caliper 12 and the caliper portion 16 will force its associated brake pad into engagement with the rotor braking surface 17 during this operation the actuating member 31 is held against axial movement by the fluid pressure acting on the face of the portion 32 thus an axial force is exerted on the adjusting member 34 by the adaptor 35 this axial force is transmitted to the housing 65 of the adjustor 34 and in turn to the drive ring 69 the drive ring 69 will by virtue of its threaded engagement with the threaded member 66 cause the threaded member 66 to rotate the degree of this rotation will be a function of the differential screw action between the internal and external threads 67 and 68 of the threaded member 66 during this rotation the ratchet action between the serrated.