In this paper the bifurcation behaviours and chaotic motions of a high-speed bogie system with and without yaw dampers are investigated. Non-smooth rail/wheel contact relation is considered in these models. And the bifurcation diagrams are constructed with gradually increasing and decreasing the speed of the bogie model under certain initial conditions. Subcritical Hopf bifurcation is found in both models, where the stationary equilibria and limit cycles coexist. Since the coexistence of multiple solutions, jumps and hysteresis caused by different levels of disturbances are found. Chaotic motions are found in the model without yaw dampers at a higher running speed.