Vernier Software and Technology
Vernier Software & Technology
Innovative Uses

Investigating Weight Distribution on a Bicycle

A bicycle is practically a rolling physics lab. From the forces you exert on the pedals to your energy output while climbing a steep road, there are hundreds of avenues for physics exploration. One investigation that works well in high school and college physics courses is investigating weight distribution of a rider on a bicycle.

Have you ever seen a cyclist get low and forward while diving into a turn? Or have you seen a mountain biker shift her weight backward when descending a steep pitch? How the rider is positioned on the bicycle is the dominant factor in determining the center of mass of the bicycle-rider system. (By comparison, a motorcycle typically weighs much more than its rider, thus the rider’s actions have a much smaller influence on the location of the center of mass.) By moving forward, a rider can place more weight over the front wheel, creating the extra friction and traction between it and the road that makes high-speed cornering possible. Likewise, a rider who moves her weight backwards when descending a steep incline keeps her center of mass between the wheels, making it much harder to “endo” (go “end over” the handlebars).

Investigating Weight Distribution on a Bicycle
Don’t have a goniometer? A photogate can measure cadence and a motion detector pedal position.

To study weight distribution quantitatively, we mounted a road bike in a stationary trainer perched atop two Force Plates. One Force Plate was for the front wheel and the other was for the rear. In the graph, you can see that without a rider, the weight was distributed fairly evenly between the two wheels. With a rider aboard, the center of mass moves rearward, with nearly 60% of the total load on the rear wheel. Once our rider started pedaling, the front and rear wheel loads oscillated by about 10%, although on average the total load was just about the same as it was while seated without pedaling.

Bicycle wheel loads
Bicycle wheel loads

The wheel load oscillations were about a quarter of a rotation out of phase with each other. This forward-and-backward loading and unloading of the bicycle is a result of the movement of the rider’s legs. By attaching a Goniometer to the rider’s right knee, we could gauge the position of the drive-side pedal and plot wheel load versus pedal position.

Wheel load and drive-side pedal position
Wheel load and drive-side pedal position

Have you ever used a Vernier sensor on a bike ride or done your own bicycle physics investigation? If so, we’d love to hear about it! Send us photos, write ups, and experiment files to, and your experiment may be in the next Caliper.

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