Owing to their high mass centre, relatively soft tyres, extreme variations in the load and load distributions during work cycles and greater flexibility of the steering system, the articulated steer vehicles (ASV) exhibit lower directional stability limits compared to vehicles with conventional steering. In this study, a kineto-dynamic model of the frame steering mechanism is formulated in conjunction with a nonlinear yaw-plane model of an articulated dump-truck. The validity of the model is demonstrated based on the available measured data. The proposed model is initially analysed to derive response characteristics of the steering system in terms of articulation angle, valve opening, strut orientations and deflections, fluid pressures and resultant strut forces and torque. The influences of variations in selected operating and design parameters on the steering system responses are investigated under a steady-turning and pulse steering inputs. The results provide important design guidelines with regard to kinematic and dynamic parameters of the steering mechanism and show that the lateral stability of the ASV is strongly influenced by the effective damping of the steering mechanism which is determined by kineto-dynamic characteristics of the articulated steering system including leakage flows across the struts piston, valve flow characteristics and struts orientations.