Make It Go: Transmission
The wheels carry you across the ground; the brakes stop you; the controls keeps you in command and the frameset holds the whole process together (while providing a nice place to sit). But what about the power, where does the thrust and the force that gives you movement come from? The simple answer is: the rider, through the transmission.
Other components of the bike can seem obvious, as they are often large in size and obvious in appearance, but the parts that make up the transmission of a bike are much less well known. This is mainly due to the fact that there are many of them, and they are often very small, or even hidden, which can give the illusion of a vastly complicated mechanism, but in reality, when each part is broken down and its job identified, understanding the transmission can be quite straight forward.
To summarise, the collective job of the parts of the transmission is to most efficiently transfer the rider’s effort (rotating the legs and pushing the pedals) to the rotation of a wheel, which in turn creates movement of the whole ‘cycle.
As with many components of the bike, the transmission can be the limiting factor when the bike is to be used for a specific purpose. You can pair up the lightest bike, with the fittest rider, but if the transmission is not correctly chosen or set up this combination will be no quicker than an off-the-rack machine used for cycling to the allotment with a basket full of plants and string.
Transmission types can vary hugely depending on the type of riding for which the bike is intended. Many parts are relatively universal, but it is often the case that the more specialist any specific part becomes for one discipline of riding, the less versatile it will be for others. For example, the transmission from a BMX wouldn’t get you up a mountain with any ease, in the same way a road racing bike transmission would last about five seconds before being smashed to pieces on a BMX bike: each type of bike requires a different set of components, for slightly different jobs.
In the sections below, the key components that make up the transmission of a bicycle are identified and described. One key consideration when reading through the parts list is that not only do different style bikes use different parts, many bikes actually may not have a lot of the components.