A KINETIC ANALYSIS OF MOUNTAIN BIKE FRONT SUSPENSION SYSTEMS

Abstract

INTRODUCTION The purpose of this investigation was to compare the effectiveness of mountain bike front fork suspension systems to control handlebar vibration and maintenance of ground-wheel contact following impact. Manufacturers of front suspension systems claim that the quality of the bike's ride is increased by maximizing ground-wheel contact and decreasing impact energy on the rider . Although suspension units are designed to perform these functions there is little scientific evidence to support the effectiveness of mountain bike suspension systems (Poole 1991, Burke 1986). METHOD Ground reaction forces and front end vibrations were recorded at the front wheel for three different front suspension systems. A rigid front end was compared to elastomer and hydraulic systems set at stiff and soft settings. A single subject performed repeated trials under controlled riding test conditions. Bike velocity and rider weight transfer were monitiored while riding down a ramp and over an AMTI force platform adapted with a 6 cm high bump. A shear quartz mode piezoelectronic accelerometer mounted to the handlebar provided vibration measurements and the AMTI force platform measured ground reaction forces at the front wheel. Mean curves for acceleration and ground reaction forces were calculated from the repeated trials and used for comparison between the rigid elastomer and hydraulic suspensions. The accelerometry results indicated that the suspension systems reduced the amplitude and frequency of vibration at the handlebar on wheel impact landing phase. Force plate measures demonstrated that the suspension units improved ground-wheel contract when compared to the rigid front end. Ground reaction force values for impact and landing demonstrate the absorption and release of energy through the suspension systems. CONCLUSION The investigator concluded that the hydraulic and elastomer systems tested did reduce handlebar vibration and improved ground-wheel contact when compared to the rigid system. ' REFERENCES Burke, E. R. (1994). Shock Treatment. M.T.B.I. 110- 112. Poole, S. (1991). Smoothing the Ride Suspension and Other Bouncy Things. Australian Cyclist. 158-14.