Abstract: A slack adjustable operator for a spring applied disc brake has a spring motor operating a disc brake through a tubular pushrod having an over-running clutch permitting axial movement of the pushrod in a brake application direction, but not in a brake releasing direction. The over-running clutch operates in longitudinal load roller slots in the outer periphery of the pushrod and having a ramp load roller retaining ring slidable laterally on the outer periphery of the pushrod, the retainer ring being retained in a stepped bore of a housing to be laterally operable, along with longitudinal operation of the pushrod for brake release only to an extent to provide normal clearance for pads of the brakes, this limitation being effective to initiate threaded slack adjustment of the pushrod to compensate for wear of the brake pads.