Abstract
Large size vehicles tend to deviate gradually from the straight course or repeat a slight deviation to the left and right on a flat and straight road. Naming this phenomenon "tottering", we have analyzed and verified that a very low relative on-center-stiffness of the steering system compared to the largeness of sprung and unsprung masses is latent as the fundamental factor of "tottering", and causes the "tottering" when combined with over-compliance characteristics of the rear suspension. This knowledge could be useful throughout the automobile industry.