A self-adjusting drum system for use with a pump or similar rotating machinery includes a balancing drum mounted on a central shaft for joint rotation therewith. The shaft extends along an axial direction and the balancing drum has an outer surface. A fixed, stationary structure surrounding the balancing drum is provided. The stationary structure has an inner surface arranged so as to face the outer surface of the balancing drum, and an annular gap is provided therebetween. A bush element is arranged in the annular gap so as to leave clearance with respect to the inner and/or outer surfaces. A fixing component is further provided for fixing the bush element to the stationary structure so as to lock the bush element against movement along the axial direction and allow it to freely move along a radial direction, inside the annular gap.