An underfloor wheel set barring machine for retreading of wheel rim circumferences of railroad wheel sets. Two driven pairs of friction rollers can be pressed against a wheel rim circumference with the friction rollers of each pair being arranged to pivot parallel to the axis of the wheel set. A drive motor has first and second smooth belt drives having a common drive wheel driven by the motor. Each belt drive has an output wheel driving an input gear of a spur gear system. Two spur gear systems have upward members respectively driving the friction rollers. The output of each belt drive is coaxially arranged with the axis of its associated friction roller.