Measurement method for stiffness of full suspension mountain bike frames

Abstract

The interest in mountain bike riding has grown significantly in the last decade. One reason is improved bike technology. Bikes are being developed faster and quality is raising. Bike manufacturers need to look for new methods to keep up with the rapid development. This project was carried out in collaboration with the German bike manufacturer Canyon Bicycles. Canyon needed a new method for measuring frame stiffness of mountain bikes. Frame stiffness has an impact on the riding experience. Canyon believed that the existing methods for measuring frame stiffness did not correlate with the riding experience of the bikes, especially regarding so-called full suspension mountain bikes. The aim with the project was to examine the perception of frame stiffness and develop a new measurement method in which the measured values would correlate with the riding experience. The subjective perception of the frame stiffness was examined in a survey study that indicated that the frame stiffness had a varying degree of impact on different riders. The riding situations in which most people seemed to be affected by the frame stiffness was when cornering or riding through rough terrain. Those two situations were broken down and quantified into the forces causing the noticeable frame deflection. The most critical load case was estimated to be lateral force on the rear wheel. The deflection caused by angled as well as horizontal lateral forces towards the rear wheel were examined through experimental testing. Eight different frames were tested, and the result were compared with a subjective stiffness reference that was created as part of the survey study. A test with a force of 450 newtons fully horizontal towards the rear wheel gave the best correspondence with the riding perceptions of the frame stiffness. More research is needed to confirm the findings and to get a better understanding of the perception of mountain bike frame stiffness