The transmission of a bicycle is a key element of a modern bicycle: this set of parts allows to advance the bicycle transforming your energy and your pedal strokes in driving force.
We present to you our complete file on the bicycle transmission: what are the elements of a transmission? How to recognize the type of transmission of your bike? Which compatibilities – and incompatibilities – are important? How to maintain and change elements?
What is the bicycle transmission system?
The transmission of the bicycle is the set of parts that allow the bicycle to move forward thanks to the pedals. Casually, this is the most technological part of your bike. If the balance bikes date from 1817, transmissions with pedals and freewheel did not see the light of day until the end of the 1860s. As its name suggests, the transmission transmits your energy to the rear wheel of the bicycle and propels it towards the bottom. ‘forward – or backward if backing up with a fixie.
The efficiency of the transmission depends on the quality of the parts used and their proper maintenance, in particular adequate lubrication. However, the proper use of gears should not be neglected to improve pedaling efficiency and to ensure the longevity of the transmission components.
What are the main elements that make up the transmission?
The main components of the transmission are the pedals, the crankset, the bottom bracket, the chain, the sprockets, the derailleurs, the gear levers and finally the cables that connect these parts.
Regardless of the model, the pedals are used to allow your feet to find support to move the cranks, which drive the crankset and therefore the chain. They are solid parts, but sometimes you have to change the pedals in case of breakage or for more comfort.
The bicycle crank
The crankset consists of one or more chainrings and cranks. The cranks are what connects the pedals to the chainring, they vary in length depending on the size of the bike, but above all depending on the size of the cyclist. The size of the chainring (s) is the determining factor for the force that will be required to move your bike. Too large a chainring requires too much force, a too small chainring forces you to pedal too quickly.
The bottom bracket
It is a room that cannot be seen. It is almost entirely within the scope of the bicycle. However, it is very important: it fixes the crankset in the frame of the bicycle. The rigidity of the case increases your pedaling comfort. Many strange noises come from a poorly maintained and lightly greased case. If you’re interested, find out all about the bottom bracket .
The bicycle chain
The most obvious element of the transmission remains the chain. Composed of metal links, the chain is the nerve center of a functional transmission. It is sometimes replaced by a belt or cardan gearing system for bikes without chains . But the principle remains: there is an element that connects the crankset to the rear wheel. We explain all the characteristics of the bicycle chain to you .
The gear gears
Sprockets are the small teeth on the rear wheel of the bicycle. Single sprocket or multiple sprockets, they are mounted on a cassette or on a freewheel, or more rarely directly screwed onto the hub of the rear wheel for a fixed bicycle. To understand everything, we explain the differences between cassettes and freewheels .
Front and rear derailleurs
Most bikes have a rear derailleur. If you see the sprockets on your bike, you can also see the rear derailleur there. It moves the chain from one sprocket to another. You change gears on your bike. If your bike has a crankset with more than one chainring, your bike has a front derailleur . This is what allows the chain to slide from one tray to another.
The gearshift levers
To change gears, you need gear levers . These levers take different forms depending on the bike model. Twist grips, levers on the handlebars or on the frame, integrated levers and brake levers. In general, it is customary to place the rear gear lever to the right of the handlebars. And so to use the left lever for the front derailleur.
Cables and gear sheaths
The commands sent by the gear levers are relayed to the derailleurs by a set of gear cables , which are protected by a specific sheath. There is one exception: some bicycle transmission systems operate by electric waves. Without cables. And therefore without regular adjustment to be made.
How to recognize its type of bicycle transmission?
The main types of bicycle transmission are: the fixie bicycle, the integrated transmission bicycle and the “regular” bicycle transmission. The latter simply refers to bikes with classic transmissions as we have just described them. In this category, we will classify the different types of speed bikes.
The fixie bike can be recognized by its lack of freewheel at the rear wheel. It is a bicycle on which the chain is necessarily driven by the movement of the rear wheel. The pedals, the chain and the rear wheel are therefore integral.
But be careful, just because you can’t see derailleurs doesn’t mean the bike is a fixie . Single speed freewheel bikes are common, for example on children’s bike models. And on bikes with integrated transmission.
Indeed, the bicycle with integrated transmission has speeds. But they are “hidden” in the hub of the rear wheel. These heavy-duty bicycle transmission systems, such as the Nexus 7-speed wheel , are increasingly common on city bikes and e-bikes .
Among conventional transmission bikes , the different systems are differentiated by their number of speeds. Usually a 10 speed bike has 2 chainrings and 5 speeds in the rear. 2 × 5 = 10, of course. This was a usual standard from the 1970s to the 1990s. Since then, the number of rear sprockets has increased every year. And there are now bikes with 10 rear speeds and two or three chainrings… In recent years, especially for MTB and Gravel bikes, the single chainring transmission with 11 or 12 reverse speeds has become common. This is referred to as a 1 × 11 or 1 × 12 transmission.
Maintenance of bicycle transmission components
There are three main stages in the proper maintenance of a bicycle transmission: cleaning , lubrication and adjustment . Preferably, these operations are carried out regularly, at least at least twice a year, and in that order.
The cleaning the chain and bicycle gears will extend the life of your chain. This simple operation only takes a few minutes, if you use the right bike care products – there are good biodegradable and environmentally friendly degreasers. Once the chain and gears are clean and dry, the lubricant is used to prevent metal-to-metal friction, which would also wear down the parts while causing unpleasant noises.
To properly lubricate the chain of the bike, you just need a few drops of lubricant on the inner side of the chain. Then shift gears to distribute the lubricant on the gears. It is also useful to lubricate the cables from time to time. We explain how in our Tutorial on the 10 point bike review . Finally, adjusting the rear derailleur requires a bit of skill, but it is quite simple by following the guide. Adjusting the front derailleur is even easier.
Eventually, it rarely happens, but sometimes, that the bicycle crankset becomes loose. You will then feel a strange float while pedaling. Find out how to tighten a bicycle crankset in just a few steps.
When and how to replace parts?
Even on a well-maintained bicycle drivetrain, parts may need to be replaced. Sometimes because of wear and tear, sometimes to increase comfort on the bike. The most common wear is on the bike chain: it must be changed when it is too loose. The steps for changing chains are the same as for shortening a bicycle chain .
With the quick links, it is really easy to change your bike chain. And even to link chains of different colors, for the pleasure of the eyes.
If your chain was too worn out, chances are the sprockets are too. Fortunately, changing the cassette of the bicycle is also a mechanical operation within everyone’s reach. Sometimes you will want to change the cogs or chainrings on the bike to change the pedaling ratio. It is a question of comfort and terrain.
The calculation of the ratio of a bike is always the same, whether for a fixie, for a classic bike or an electric bike.
Do your front or rear derailleurs never seem to work well, despite a good adjustment? It’s probably time to replace the derailleur cables and housings . And for both comfort and wear, learn to change the pedals of the bike or more simply, to tighten the pedals .
About the compatibility of brands and types of transmissions
Of course, if you modify the parts of the transmission, you will be faced with the question of the compatibility of the new parts. And above all, the incompatibility problems. The first thing to check is the number of reverse gears on the bike. Indeed, the chain widths vary according to the number of sprockets. If you are changing a derailleur or shifters, see our guide to shifters .
You should know that the length of cable pulled by the levers varies between brands. It is therefore not recommended to use levers and derailleurs of different brands, unless you have the indication of the pulling length.
For mechanics more accustomed to major repairs, it is possible to change the bicycle bottom bracket . But you must then correctly calculate the chain line to keep an optimal fit.