Abstract: An automatic air gap readjusting assembly in a clutch or brake unit is operated by electromagnetic and spring forces. A drive shaft 3 frictionally mounts, by a plurality of O-rings, an adjustment member. The adjustment member is readjusted by a contact or armature plate such that the air gap between the armature plate and the electromagnetic mechanism attracting the armature plate will remain constant, i.e. the stroke of the armature plate will remain constant. Torque is transmitted from the drive shaft to the armature plate via a radial flange having a plurality of axially movable torque transmitting bolt assemblies, which are clamped to an annular spring member secured to the armature plate. This arrangement allows for continuous readjustment for wear of the air gap between the armature plate and the electromagnetic mechanism; furthermore, the readjustment always takes place under uniform force conditions despite increasing wear.