As the size effects of wheels are crucial to the practical applications of vehicle-scanning method in the presence of pavement irregularity, a miniature vehicle model incorporating size of two wheels in a three-mass vehicle model is proposed in this work. The feature of the vehicle model lies in the two rigid wheels having both mass and dimension, which is seldom discussed through the analytical approach. A numerical procedure is established to locate the real contact points and contact displacements during simulation. The significance of the proposed vehicle model is investigated through the parametric study by considering the size effect of wheels, effect of vehicle damping, pitching effect, etc. For the present vehicle model, it is shown that the first three bridge frequencies can be scanned clearly under the condition of pavement irregularity.