Abstract: A retractable rear bumper means for attachment to the rear of self-propelled dump trucks having boxes which overhang the rear axles and extend rearwardly thereof, with the bumper means being coupled to the frame of the box and arranged to fold upwardly upon initiation of the raising of the dump truck box to a raised dumping position. The bumper means includes a bumper bar which extends transversely across the rear of the dump truck and has a length which exceeds the inner tread width or span of the rear wheels of the truck, and linkage means are provided to retain the bumper bar in a normal stable distended disposition, and to raise the bumper bar in response to initiation of raising of the dump truck box. Linkage arms and means are provided for retaining the bumper bar in the lower disposition, and also retaining the bar in its upper retracted disposition during the dumping operation.