:A computer simulation was performed at Iowa State University on a twin trailer combination. A general purpose multi-body dynamics program was used. Steer inputs were modeled after actual driver data collected at the wheel end of a vehicle. Input was held to a constant frequency of 2.2 radians/second while the amplitude was increased until rollover occurred. Rollover occurred when the tangential tire forces reached zero at the rear axle of the rear trailer. Major improvements were noted when the freeplay was removed and the width of the suspensions were increased by 6 inches.