A device for adjusting the prestress of an elastic means around a predetermined tension or position can especially be used to adjust the height of and the relief force acting on a weight. A mechanic adjustment unit is connected in parallel to the elastic means to preadjust the value of the predetermined tension comprising a movable portion engaging the connection portion between elastic means and adjustment unit and a force exerting element being attached at said movable portion. The mechanic adjustment unit is in an unstable equilibrium position at said predetermined tension or position, the movement of the movable portion being such that the force exerting element adds an adjustment or compensation force upon deviation of the predetermined tension or position of the elastic means.