Loosening of the wheel bolts may be the cause of accidents where the wheel falls off while the trailer is running. When the transverse force exceeds a certain proportion of the bolt shaft force, the wheel nut begins to loosen. On the other hand, it is clear by the numerical analysis that the transverse force as it self is influenced by the condition of bolt fastening. In this report, more suitable transverse force is searched by thinking out the method of bolt fastening.