Understanding bicycle transmission

How does a bicycle transmission work?

The classic transmission on a bicycle is simply a chain which starts from the crankset and which allows the transmission of the force from pedaling to the rear wheel. This is what you find on a fixie.

Transmission developed with the invention of the derailleur system. That is to say, a bicycle is equipped with sprockets and chainrings of several sizes, one or more derailleurs and shifters.

The rider manipulates the shifters while riding to change gears as needed. To fully understand the gear system, let's go back to the transmission components.

The transmission consists of the following parts: derailleurs (front and rear, including the cage), cassette, chain, shifters...

If you are riding in mountainous terrain and you are a novice, it would be wise to think about equipping your mount with a compact crankset and a large sprocket with the maximum number of teeth (depending on the length of the cage). of your rear derailleur).

Composition of a bicycle transmission

- The gears

The sprockets of a bicycle are small toothed wheels located on the rear hub of the bicycle. The chain is positioned on one of the sprockets to drive the wheel. They are mounted on the wheel using a freewheel or cassette system.

There are several sprockets on a geared bicycle (except on the bicycle with gears integrated into the hub). The sprockets, grouped in the form of a cassette or freewheel, are the toothed rings which allow the chain to be driven on the rear wheel. They are mounted on the wheel hub using a freewheel or cassette system.

The freewheel mechanism is one that allows you to pedal and drive the wheel, but also to stop pedaling without braking the bike.

- A Boxes is made up of separate pinionsar fixed or mobile spacers. The assembly is inserted into a freewheel body, itself screwed into the hub of the rear wheel.

- A freewheel is a single block including the freewheel mechanism and the pinions. This assembly screws onto the rear wheel hub. Freewheels are cheaper, heavier, and typically used on older or low-end 5 to 8-speed bikes (very rarely nine-speed).

To facilitate explanations, the word “cassette” is used to refer to all the sprockets.

- Trays

The chainrings are the large toothed wheels attached to the crankset. We find between 1 and 3 chainrings, depending on the type of transmission of the bike.

When the cyclist pedals, he rotates the crankset, and drives par consequently the plateau. The smallest chainrings that can be easily found have 22 teeth, the largest 56 teeth (usually reserved for road bikes). The crank is the name given to the arm of the crankset onto which the pedal is screwed. Your bike therefore has two cranks, the right and the left.

- Shifters

Shifters allow the cyclist to operate the derailleurs of their bike. Several controller systems exist. Rotating handle systems are rarely found on travel bikes because they are rather low-end, except of course the Rohloff hub lever.

The most common gear shifters on travel bikes have small levers that you simply push or pull with a flick of your fingers. By turning the handle or operating the lever, you modify the tension of the cable which pulls on the derailleur. As a general rule, the gear levers are on the right on the handlebars, the chainring levers are on the left.

- The derailleur

Indispensable element on speed bikes (except bikes with integrated gear hub) moves laterally to guide the chain towards another chainring or sprocket, when... ™we activate the derailleur lever.

We find a front derailleur, to change the tray, and a rear derailleur, to change gear. The rear derailleur plays two different roles.

By activating the control placed on the right on your handlebars, the rear derailleur will move the chain up and down. It’s thanks to him that we change gears. It also helps maintain chain tension. In other words, it prevents your chain from draggingar ground when you go from a very large cog to a very small one. Indeed, without this spring effect, the chain would either be too long on the small sprockets, or too short to mount on the large sprockets.

The part of the derailleur which acts as a chain tensioner is called the cage. This is the lower part of the derailleur connectedar two rollers (two small plastic casters). The length of a rear derailleur's cage determines how many teeth of the sprocket + chainring system it can support. The small yokes are made for cassettes with limited pitch, that is to say where the distance between the smallest and largest pinion is limited. Road bikes generally have short cage derailleurs and mountain bikes have long cage derailleurs.