In order to reduce torsional vibrations and wheel slip in a wheel set for a rail vehicle the wheel set comprising a pair of wheels connected by an axle is provided with a vibration absorbing device comprising a mass, resiliently mounted on the wheel set and adapted to oscillate at the resonant frequency of torsional vibrations of the wheel/axle system. A method of preventing or reducing torsional vibrations in a wheel set of a rail vehicle is also disclosed, the method comprising determining the resonant frequency of torsional vibrations of the wheel/axle system and resiliently mounting a vibration absorbing device in the form of a mass, on the wheel set, the mass and its resilient mounting being selected to oscillate at or near that resonant frequency.