Abstract
Motorcycle frame flexibilities greatly affect the straight running stability. Conventionally, the effects of these have been analyzed using a mathematical model in which multiple frame flexibilities are combined. In this paper, it is proposed that a method for analyzing the effect of a single frame flexibility (5 degrees of freedom model) on straight running stability from a composite frame flexibility model (10 degrees of freedom model). Specifically, it is described that the influence of individual frame flexibility can be estimated using the one based on the analysis model in which all the frame stiffness values in the 10- degree-of-freedom model are extremely large.