How do bikes work?

How do bikes work? In short, pedals, gear system, wheels, handlebars and brakes enable you to cycle safely and bikes’ geometric shape enables it to stay upright in motion. The authors of this article both have bikes and tested the common misconceptions on how bikes work themselves. We believe that understanding how each component functions and how it contributes to the stability of the mechanism is the key to understanding how bikes work. For this reason we have explained how each bike component works separately. These components include: pedals, gear system, wheels, handlebars and brakes. In the last section of this article we have explained the science behind bikes staying upright in motion. 

How do bike pedals work?

Where it all begins..Pedals are the bike components that you apply force on to move the bike forward. They are attached to the cranks on both sides of the bike and the cranks convert the force you apply into rotational movement. While cranks are attached to bike pedals on one end, they are attached to chainstay on the other end. And the chainstay transitions the rotational movement of the crank to the bike gear system. 

How does a bike gear system work?

The bike gear system simply transitions the rotational movement you generate by pressing on the pedals to the rear wheel. The bike gear system also enables you to adjust the force needed to apply to the pedal to have the rear wheel turn just once. The gear system consists of several components including cassette, chainring and chain. 

How does cassette, chainring and chain work?

Chainrings are connected to the cassette with a chain and the cassette is the collection of kongs or sprockets attached to the rear wheel. Shifters and derailleurs enable you to change the gear that the chain is on at the cassette and chainring inturn enables you to adjust the force you need to apply on the pedal to spin the rear wheel of your ride.

How do shifters and derailleurs work?

Shifters are located on the handlebar and are connected to the derailleurs through cables. By clicking on the shifters you can pull the cable tighter which in turn pulls the derailleurs and changes the location of the chain to a smaller gear. Also by clicking on the other shifter you can release the cable which changes the location of the chain to a bigger gear. Lowering the gear would be ideal for uphill cycling as shifting the chain to a lower gear would decrease the force needed to move the bike forward.

How do bike wheels work?

Bike wheels support your weight. The taller the diameter of the wheel the longer distance you can go at one wheel turn. This is the reason why race bikes have larger wheels and adult bikes go faster than child bikes. If the bike wheels were entirely solid without any spokes they would compress as you sat on the seat and push you back up. On top of this, the spokes make the wheels lighter, stronger and lessen the drag force in movement.

How do bike handle bars work?

The handlebar for a bike has two main functions: controlling the steer and supporting the rider. Bikes’ handlebars are mechanically connected to the front wheel via a stem and fork so that when the rider rotates the handlebar the front wheel rotates as well. In addition to this, depending on the rider’s position the handlebar may provide significant support for the rider’s weight.

How do bike brakes work?

Can you imagine a bike without a good brake mechanism? We cannot and don’t want to. Bike brakes convert kinetic energy into heat energy through friction. There are two main types of bike brakes: rim brakes and disk brakes.  Bikes with rim brakes have a pair of rubber shoes both on the front and rear side that have the inner rim of the wheel in between. When the rider squeezes the clamps, rubber shoes get in contact with the inner rim, convert the kinetic energy into heat energy and slow the bike down. Bikes with disk brakes have two pads both at the rear and the front side of the bike that have the disk attached to the wheels in between. When brake levers are pressed the pads squeeze the disk, transform kinetic energy into heat energy and slow the bike down.

How do bikes stay upright? 

Magic, mystery or science? There are misconceptions about how bikes stay upright. Main misconceptions are that bikes stay upright due to conservation of angular momentum and forward momentum. Conservation of angular momentum explanation suggests that as the wheels are spinning if the bike leans to one side there would be a reaction force from the wheels to keep the bike upright. This explanation is wrong because if you lock the handlebars of a bike and push it forward like a stationary bike the moving bike will fall over. Forward momentum explanation is also wrong because if you slightly push a ghost-riding bike from the side it will change its direction and keep moving, changing its momentum. (Ghost-riding refers to pushing the bike to get it to move forward as opposed to pedaling on the bike to give it momentum).

If you push a bike forward it will stay upright because when it leans one side the handle bar will steer towards that side by itself. There are 3 factors that enable this: the front wheel contacting the ground behind the steering axis, the weight center of the handlebars and front wheel, which is located in front of the steering axis and the Gyroscopic effect. The front wheel touches the ground just behind the steering axis. The upwards reaction force from the ground turns the wheel towards the direction it’s leaning towards, helping the wheel to return underneath its center of gravity. The weight center of the handlebars and front wheel being located in front of the steering axis also enables the bike’s tires to steer towards the direction it is leaning. And lastly the Gyroscopic effect from the wheels helps wheels to steer towards the direction the bike is leaning. Gyroscopic effect is the physical effect that steer the handlebars towards the direction that bike leans against bringing the wheels back to its original position and helping to keep it upright.

how do bikes work
The front wheel touches the ground just behind the steering axis.

Final Thoughts

We hope this article explains how bikes work clearly. Even if you are not a biker yet and just interested in this lifestyle or science, it is never too late to start. For those of you are new to the cycling world, we compiled the following list of informational content you might find useful: How to choose a bike?, Benefits of cycling and more.

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