A unit (1) for supporting the axle-shafts of go-karts provided with an annular body (12) having a variable perimeter and with a rolling bearing (20), set within the annular body (12) itself with the possibility of oscillation about an axis of adjustment (B) transverse to an axis (B) of rotation of the bearing (20) itself; a tightening system (30) being provided for tightening the support (11) on the bearing (20) and for blocking the bearing (20) itself in an operative position, and being defined by at least two sharp edges (32) (33) (36), fixed with respect to the bearing (20) and set about the axis (B) of rotation for cutting into a softer material of the concave seat (13), preventing any rotation of the bearing (20) about the axis (A) of adjustment in said operative position.