The study of the tyre-terrain interaction is a very important subject of research for off-road vehicles, since the tractive performance, steer ability and handling are of great interest to overall performance. The interrelationships between the performance of an off-road vehicle and its design parameters and terrain conditions provide guiding principles for the rational development and design of off-road vehicles to suit particular operation requirements. The tyre model of lateral and longitudinal slip for an off-road tyre has been extended to include lateral, longitudinal slip and yaw for cambered tyre. The study leads to a complex model but the model gives predicted values for tyre forces and moments in the three directions, and thus is helpful to understanding the tyre behaviour in this complex case. So, the six components of forces and moments actingfrom the deformable surface to the tyre were investigation. A computer program in MATLAB software was developed to complete the study. The results are shown as tyre forces and moments in the three directions along the tyre contact length . The effect of some model parameters on off-road vehicle performance was studied. The results indicated that although the spokes tyre model becomes more complex, it begins to provide a better understanding of the complex phenomenon of the interaction between off-road tyre and soil.