A method for operating a rotating machinery comprising a rotor, a rotor shaft, and at least one journal bearing supporting the rotor shaft is disclosed. The bearing comprises a bearing housing, a bearing surface in the bearing housing, a sleeve torsionally and axially fitted on the shaft, and a lubrication oil film filling a clearance between the outer surface of the sleeve and the bearing surface. The method comprises the step of modifying the clearance by modifying a radial dimension of the outer surface of the sleeve as a function of a rotation speed of the shaft.