Modelling and Optimizing Folding Bicycle Suspension for Rider Comfort (ISO 2631)

Abstract This study focuses on developing a dynamic model of the rider–folding bicycle system equipped with a rear suspension, based on the geometric parameters of the commercial Fornix F160 bicycle and pivot point locations referenced from the work of Good and McPhee. The equations of motion, derived from the second kind of Lagrange equations, are numerically solved using the Runge–Kutta method to determine the rider’s acceleration response, which serves as a key indicator for evaluating ride comfort. The reliability of the dynamic model is validated by comparing its results with simulations conducted in Altair Inspire software. Following model validation, the defined dynamic model is employed to quantify rider comfort through vertical acceleration responses, in accordance with the ISO 2631 standard. The analysis is conducted under two excitation conditions: irregular road surfaces defined by ISO 8608 and cluster-type speed bumps specified in TCCS 34:2020. Based on this setup, the study investigates the influence of rear suspension parameters ( c; k ), aiming to identify the optimal configuration that enhances rider comfort. The results demonstrate that the proposed model significantly improves ride comfort, with enhancements of up to 88.57% compared to a rigid-frame bicycle. These findings have informed notable structural modifications to the frame design relative to the original folding bicycle configuration.