the lower end of the piston i e near the crankcase end of the piston both of the rings 16 and 18 are circumferentially sized so as to form a tight seal with the cylinder wall to this end a variety of expanders or expansion rings or expander springs as are well known in the art can be employed on the inner surface of the rings 16 and 18 so as to force the rings into sealing engagement with the cylinder wall the ring 18 is axially spaced from ring 16 so as to form an axially extending space 22 between the rings 16 and 18 in operation combustion gases are trapped in space 22 to form a gas bearing b 22 for the piston 12 with the result that the piston is separated from the cylinder wall by a film of air thus dispersing with lubrication by oil the axial distance between rings 16 and 18 can vary depending on piston size thrust load and relative location of the piston at the bottom dead center with respect to the bottom end of the cylinder liner preferably the axial distance between the rings 16 and 18 is such as to provide a large gas bearing b for the piston for example in an internal combustion engine having a 5 5 inch bore piston length of 6 inches and the peak thrust load of 2 500 pounds the axial distance between rings 16 and 18 can suitably be at around 4 0 inches in an optional embodiment of the invention a third annular oil ring 20 is provided on the piston ring 20 can be a conventional type oil ring which serves to distribute a thin film of lubricating oil to the cylinder.