In devices such as disk brakes, a lining is moved into contact with the brake disk by way of a piston.  It is conventional to provide a spring for returning the piston to its original position.  Under a number of circumstances, the springs do not perform their intended function whereby the linings frictionally contact the brake disc even when no pressure is applied to the pistons. 
The present invention solves that problem by providing a sealing ring which retracts the piston for a predetermined distance which is sufficient to prevent the linings from remaining in contact with the brake disk.  For relevant prior art, see U.S. Pat.  No.  4,058,084 wherein the groove for the sealing ring is non-conventional and/or a spring is provided in the groove with the sealing ring.  The sealing ring of the present invention is designed to be used in a standard groove with the sealing ring performing the added function of acting like a return spring.  Also see U.S. Pat.  No.  3,771,801 wherein the seal disclosed therein bears a superficial resemblance to the seal of the present invention.