The control method used by humans to ride and balance a bike is still a mystery. Researchers have used mathematical equations to explain how a motorcycle without a driver can balance itself. They have also identified features of the bicycle that are critical.
The stability of a bike and its rider is difficult to quantify or describe mathematically. This is especially true because rider abilities can vary greatly. We brought in expert and novice cyclists to the lab and investigated if they used different balancing methods.
Physics of riding a bike upright
Controlling the center of mass is a key part of balancing the bicycle. The center of mass can be defined as the point where all mass (person and bicycle) is concentrated. The rider should always maintain the center of mass above the wheels or the base of support, which is an imaginary polygon connecting the two tires’ contacts with the earth.
Can be used by cyclists to balance their bikes. These strategies are body movement and steering. The steering is essential for maintaining balance. It allows the bike to move and bring the base support under the center mass. Imagine trying to balance a broomstick with one hand. Steering a motorcycle is the same as the hand movements required to maintain the broomstick’s balance. The rider can drive the bicycle directly by using the handlebars.
Leaning left or right has a smaller impact than steering. However, it allows a rider to make corrections to their balance by moving the center of mass from side to side in relation to the base of support and bicycle.
Balance is achieved by steering, but not through body movements. There is no combination of both to achieve balance. Karl von Drais, inventor of the Draisine, noted that the basic strategy for balancing a bike is to steer the bicycle into the unwanted fall.
Newbies versus pros
Although mathematical equations can describe riders, these equations cannot yet be used to predict the stability of riders on bicycles or understand the differences between riders with different abilities.
My colleagues and I recently worked to examine the types of controls used by novice and expert riders and identify differences between them. In our study, experts were defined as cyclists who had mastered the sport, regularly trained, belonged to cycling clubs or teams, competed multiple times per year and used rollers indoors. The novice riders were able to ride a bike, but only for transportation or recreation. They did not consider themselves experts.
In our experimental setup, a subject rides the instrumented bike on training rollers. Cain SM. Ashton-Miller JA. Perkins NC. (2016). On the Skill Of Balancing While Bicycling. PLoS ONE, 11(2): e0149340. CC BY
Our experiments were conducted in a motion-capture laboratory where riders rode typical mountain bikes on rollers. The rollers restrict the bike’s forward-aft movement, but allow it to move freely in both directions (left-right). The rider must maintain their balance using pedaling, steering, and leaning as they would outside.
The subject is preparing to ride our instrumented bike. Stephen Cain CC-BY-ND
We used sensors mounted on the bike and a motion-capture system to measure its motion (speed, steering rate and angle, roll rate and angle) and the steering force used by the rider. We used a force platform under the rollers to calculate the lateral location of the center mass relative to the support base. This allowed us to determine the rider’s lean.
Both novice and expert riders have similar balance performances at low speeds. At higher rates, however, expert riders are able to achieve better balance by using smaller body movements that are more effective and by steering less. Expert riders, regardless of speed, use less body movement and smaller steering inputs.
We conclude that experienced riders can use their body movements more efficiently than novices, which reduces the need for large steering corrections and body movements.