In this paper, the effects of the Cornering Stiffness (CS) variation on directional stability of the Articulated Heavy Vehicle (AHV) are examined through analysis and simulations. The CS is one of the most important parameter which has a considerable effect on vehicle dynamic behavior. On the other hand, due to the physical nature of the tyre, the CS varies significantly in response to the braking or driving torques applied to the wheels. Therefore, there is a vital need to study the effect of the CS variation on directional stability of AHVs. A linear planar model of articulated vehicle is used to investigate the effects of CS variation on directional stability. Furthermore, the results derived by this analysis are confirmed through lane change maneuver simulation by a full nonlinear planar model of the articulated vehicle. The results achieved in this paper can be used to develop an appropriate procedure for braking or driving forces distribution.