A sealing assembly that significantly reduces or eliminates blow-by, peristolic pumping and sealing element flutter while, at the same time, reducing to ultra low levels friction between the sealing element and its assembly. The assembly has surfaces in at least one of the bore wall or piston to form a groove facing the other of the wall or piston, the groove having exposed smoothly curved shoulders which face each other. A sealing element is positioned in the groove, the element having smoothly curved side surfaces mateable with the groove shoulders for supporting the element in the groove. The sealing element has an exposed outer surface (crown) which also is smoothly curved with a pair of mirror image shoulders, The crown is effective to tangentially contact the cylinder wall while the element side surfaces each tangentially contact their respective mating groove shoulders. The pair of mating groove shoulders and element side walls each have defined curvatures which are effective to maintain the tangency and transfer any load from the sealing element (resulting from contact between the element crown and the cylinder wall contact) to the groove shoulders in a substantially equal manner regardless of articulation of the element in the groove. The curvature of the groove shoulders side surfaces and crown surfaces all adhere to a tractrix relationship.