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Vertical Displacement and Velocity Change While Mountain Biking: Comparing Suspension Forks to a Rigid Front Fork

1 May 1998


Most mountain bikes offer the choice of suspension. Suspension is designed to improve rider performance by attenuating rough terrain. Various components are used to construct front suspension forks, but no published data exist on fork performance differences under identical riding conditions. The purpose of this study was to examine two front suspension forks marketed for cross country riding and compare their performance with each other and with a rigid fork. Nine experienced mountain bike racers rode a rigid frame bike (RIG) and two suspension bikes with different front forks (FSl, FS2). Subjects performed five trials per bike. They began each trial by pedaling at the speed of their choice, then coasting between two markers 8.76 meters apart. A 2.74 meter bumps course was placed at the midpoint of the two markers. The course consisted of four wooden bumps of various shapes ranging from 4.0 to 8.3 centimeters in height. Sixty Hz video analysis revealed the velocity change of the bike before (PRE), during (ON), and after (POST) the bumps course, as well as the maximum vertical displacement of the front hub of the bike and the wrist of the rider over the bumps. A blocked factorial ANOVA of the vertical displacements revealed no interaction between the type of front fork on the bike and the maximum vertical displacement of the wrist or the front hub (Wrist: p=0.30, Hub: p=O.lO). A repeated measures ANOVA of the velocity data revealed no significant difference between the three bicycles in change in velocity PRE, ON, and POST (p=.82). This study was designed to analyze a realistic change in vertical displacement as the rider completed a continuous 2.74 meter stretch of bumps. The fact that the overall change in vertical displacement of both the wrist and front hub were measured as opposed to measuring the change over each individual bump, this may contribute to the lack of significant difference between bikes. This study neither confirmed nor refuted the findings of other studies on the effectiveness of front suspension on mountain bikes. It is possible that a suspension fork attenuates the abrupt change in velocity as the bike contacts a bump, but does not decrease the overall change in velocity or vertical displacement of the bike throughout the ride in this study.


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