Abstract: A bicycle shock absorber includes a cylinder body which confines a sealed space therein and a valve member which is disposed movably in the cylinder body and which divides the sealed space of the cylinder body into an air chamber that contains high pressure gas, and a fluid chamber that is filled with hydraulic fluid. The cylinder body is formed with a vent hole to access the air chamber and has a plug for sealing the vent hole after the high pressure gas has been introduced into the air chamber. A piston shaft has a connecting section which extends into the fluid chamber, and a piston is retained on the connecting section of the piston shaft and is formed with a plurality of axially extending fluid holes therethrough. A restoring member is disposed outside the cylinder body and is associated operably with the piston shaft and the cylinder body so as to bias the piston shaft outwardly of the cylinder body.

Abstract: A shock absorber includes an outer tube filled with hydraulic fluid and an inner tube that extends into the outer tube and that contains an appropriate amount of hydraulic fluid and high pressure air therein. A piston is secured to an open bottom end of the inner tube and is formed with a central through hole and a plurality of fluid passages which communicate the inner and outer tubes. The piston further has a bottom surface which is formed with concentric first and second annular grooves and an annular wall that separates the annular grooves and that is formed with a notch to communicate the annular grooves. The fluid passages extend into the first annular groove. The second annular groove has a depth that increases gradually from one side of the notch to an opposite side thereof. A control rod is disposed inside the inner tube and has a bottom end that extends through the central through hole of the piston.