The motion of a simple wheelset is discussed whereby the wheelset is thought to move on a tangent track, except for small lateral periodic variations of the track centerline. The wheel profile is approximated by third degree polynomials, such that the wheel contour fits two points of the actual profile, namely those where the slopes are maximum (~ 38. 1mm from tapeline) and near minimum (12.7mm from tape-line). The study seeks to determine the motion domains of stable and unstable limit cycles by analytical means and by the use of an analog computer model. The model that is employed is one of two degrees of freedom, considering lateral and yaw motions of the wheelset.