Revealing the Impact of Motorcycle Caster Angles on Weave and Wobble: A Comprehensive Analysis through Visualized Stability Testing 2024-01-2770

Since it takes a long time to design motorcycles in order to prevent weaving and wobbling, which are self-excited oscillations, this paper aims to shorten the design process. The reason for the extended duration is that the weave and wobble strongly depend on ‘forward speed’ when the design variables are altered. Therefore, this paper focuses on speed and visualizes the region where self-excited oscillation does not occur for each design variable as a function of vehicle speed. The results demonstrate that at high speeds, the caster angle and steering damper are the only design variables for which this region exists near the design value. Due to the narrowness of these sweet spots, they become the most crucial variables in the design. However, this paper solely considers the caster angle as the most important design variable, as the steering damper adversely affects handling. In addition to the caster angle, the design variables with the most significant effects in the regions for changes in design variables are the trail and front tire radius, the moment of inertia of the front wheels, and the relaxation length of the front wheels. As an illustration of a design that utilizes these variables, this paper demonstrates the elimination of self-excited oscillation at high speeds by adjusting the caster angle and trail. Consequently, by concentrating on the caster angle’s sweet spot where self-excited oscillation does not occur, weaving and wobbling at high speeds can be eliminated in a short time. As a result, weaving and wobble at high speeds can be eliminated in a short time by concentrating on setting the sweet spot of the caster angle that does not cause self-excited oscillation.