the caliper leg 23 so as to permit adjustment for wear return spring arrangements as was described in the aforenoted u s pat no 3 768 603 are also provided for returning the brake to its at rest position this arrangement includes a pin 46 that is fixed at one end to the backing plate 41 and which has an enlarged head 47 that extends into a bore of the sleeve 43 a coil compression spring 48 urges the pin 46 and associated brake pad 36 to its released position operation of the brake assembly is provided by a mechanically actuated lever cam 51 the cam 51 is comprised of a pair of spaced interconnected arms 52 and 53 the arms 52 and 53 are pivotally supported relative to the mounting bracket 16 by means of a pivot bolt 54 the arms are formed with enlarged central openings 55 to pass the shaft which drives the rotor 12 not shown the arms 52 and 53 are also connected by a bolt assembly 56 which passes through the head of a threaded rod 57 to provide a release spring arrangement the rod 57 extends through an upstanding end 58 of the support leg 19 and is encircled by a coil compression spring 59 the spring 59 bears against a shoulder 61 formed on the rod 57 and the bracket end 58 a nut assembly 62 permits adjustment of the angular position of the lever 51 and preload of the spring 59 for shipping and installation the nut.