Abstract: An automatic balancing device for rotary units or systems. The automatic balancing device includes an annular housing, and an annular outer race track disposed in the annular housing. The outer race track is concentric with and attachable to the rotary system so as to rotate with the rotary system. A number of roller bodies are disposed in the annular housing and are freely movable along the race track for dynamic and/or static contact therewith during rotation of the rotary unit or system. The outer racetrack is provided in a separate ring of a large diameter having a torus-shaped groove forming the race track and having a curved concave profile facing the center of the separate ring.