Beyond pedal kickback: analysis and categorization of crank torque in downhill mountain biking

Abstract The interaction of contact forces between the rider and the bicycle, particularly at the feet and hands, is crucial for the riding experience and safety during standing descents in downhill mountain biking. While numerous technical solutions have been developed to mitigate unwanted forces transmitted to the rider’s feet via pedal kickback, current research shows that pedal kickback is speed-dependent and rarely occurs at typical downhill speeds. This raises the question of whether other, previously unidentified mechanisms are responsible for generating these forces. This study resolves this contradiction by equipping a downhill mountain bike with suitable sensors and identify three additional mechanisms, beyond classical pedal kickback, that can generate crank torques. Crank torque was used as primary parameter for the influence on the rider, as it reflects disruptive forces transmitted via the drivetrain, independent of the rider’s riding behaviour or mass distribution on the pedals. Objective classification criteria are described for these categories, supported by schematic representations and exemplary measurement data. These categories could form the basis for a more differentiated assessment of the relevance of pedal kickback and could enable an objective evaluation of the effectiveness of anti-kickback systems, because they differ in their mode of operation. In addition, the knowledge could be used by manufacturers to optimise suspension and drivetrain designs, as well as to interpret rider feedback during heuristic testing. Finally, the categorisation could also benefit professional riders by helping them to better understand their subjective impressions and, where necessary, adapt their riding technique to minimise disruptive forces.