Vibration damper with amplitude-selective damping force

A vibration damper includes a damping medium filled cylinder in which a piston rod carrying a working piston is guided with freedom of axial movement, the working piston dividing the cylinder into two working spaces. The piston rod forms a housing having an inside wall, the housing having first and second working chambers separated by a separating piston, the first working chamber being connected to one of the working spaces to provide amplitude selective damping as the working piston moves in the cylinder. The separating piston is spaced from the inside wall to form an annular gap in which a pressure gradient develops when the piston rod moves, thereby causing the separating piston to move in the housing, the separating piston being radially expandable to close the gap when sufficient pressure develops in one of the working chambers.