Minimization of Pedaling Induced Energy Losses in Off-road Bicycle Rear Suspension Systems

This paper presents the results of an optimization analysis performed on off-road bicycles in which the energy loss induced as a result of pedaling action was minimized. A previously developed computer-based dynamic system model (Wang and Hull, Vehicle System Dynamics, 25:3, 1996) was used to evaluate the power dissipated by a single pivot point rear suspension while pedalling uphill on a smooth surface. By systematically varying the location of the pivot point, the relationship between power dissipated and pivot location was determined. The optimal location was defined as the location which resulted in the least power dissipated. The simulation results show that the power dissipated was very dependent on the height above the bottom bracket but not the fore-aft location of the pivot point. If the pivot point is constrained to the seat tube, then the optimal pivot point was found to be 11 cm above the bottom bracket. Compared to a commercially available design, the optimal pivot point reduced the power dissipated from 6.9 to 1.2 Watts. Furthermore, the optimal pivot point was found to be very insensitive to pedaling mechanics, and both the spring and damping parameter values. The optimal pivot point did, however, have a linear dependence on the height of the chainline; as the chainline height increased so too did the optimal pivot point height.