This paper presents a mathematical approach for creating a vehicle model incorporating the characteristics of tires, suspension, forces acting at the tire/road interface, suspension forces, wind forces and gravitational forces. The model has been made for a middle class limousine. Two sets of equations, one set for the translatory motion and the other set for rotational motion have been derived. Torques, forces and angular or longitudinal velocities have been chosen as variables to act as interface between different sub - models. The complexity of the vehicle model created has been optimized for vehicle dynamics simulation. All the forces have been found in the undercarriage co-ordinate system. While substituting them in the equations of motion they are multiplied with the transformation matrix for the transformation from the undercarriage to the inertial co-ordinate system.