Study of the frame stiffness influence on vehicle dynamics and stability of light commercial vehicle is done. The simulations were conducted by using ADAMS/CAR software package. The model approbation was carried by comparing the results of simulation and real tests. The objects of the studies were four different models of a vehicle having different parameters of the frame rigidity. For the needs of the research where conducted such tests as: "going into corner", "line change" and "tilt test". The results showed that a car with a rigid frame has better handling properties.