Effects of selected mountain bike front suspension forks on handlebar vibration and ground reaction forces

Abstract

The purpose of this investigation was to compare the effectiveness of two types of mountain bike front fork suspension systems for controlling ground reaction vibration at the handlebar upon impacting a raised surface. A second purpose was to investigate the effectiveness of these two suspension systems at maintaining ground-wheel contact following impact This investigation provided a direct measurement of handlebar vibration and ground reaction forces at the front wheel. A rigid front end was compared to an elastomer and a hydraulic suspension system each tested at their stiffest and softest settings. A single subject was chosen to perform repeated trials over an AMTI force platform modified with a 3 cm raised surface. Velocity and riding technique were controlled for reliability and rider weight displacement was measured using strain gauges mounted on the handlebar. A shear quartz mode piezoelectronic accelerometer mounted to the handlebar provided vibration measurements and the AMTI force platform measured ground reaction forces. Mean curves for acceleration and ground reaction force were recorded and calculated from repeated trials and used system comparison. Results from the mean curve comparison of the suspension systems showed reduced amplitude and frequency of vibration at the handlebar and improved ground/wheel contact time for both elastomer and hydraulic systems when compared to the mean curves for the rigid front end. Statistical analyses supported the mean curve results indicating significant differences between the rigid and the suspension systems on all variables analysed at the .05 alpha level. It was concluded that the hydraulic and elastomer systems reduced handlebar vibration and improved ground-wheel contact when compared to the rigid systems for this particular subject and bike combination. This investigation supports claims made by manufacturers of suspension systems, that front suspension improves ground/wheel contact and reduces transmission of impact energy to the rider at the handlebar.