What is the main function of a Bicycle Rear Derailleur?

The core function of a Bicycle Rear Derailleur is to control the position of the chain on the rear cassette. By adjusting the rear derailleur, the chain can be moved between different gears on the rear cassette, changing the speed ratio of the bicycle, allowing the rider to choose an easier or more powerful pedaling frequency. Generally, smaller gears are suitable for flat roads or high-speed riding, while larger gears are suitable for climbing or slow-speed riding.

When a rider encounters uphill, downhill or flat roads, by adjusting the rear derailleur, he can choose the appropriate gear for easier riding. For example, when going uphill, by switching to a larger gear, the pedaling frequency can be reduced and the climbing efficiency can be improved; while when going downhill or on flat roads, switching to a smaller gear can increase the riding speed and reduce the pedaling frequency.

The rear derailleur of modern bicycles is usually designed with smooth speed change in mind. Through precise adjustment, the rear derailleur can ensure that the chain moves smoothly without jamming or chain jumping, providing a more comfortable and efficient riding experience. Proper adjustment can make the chain transition smoothly when changing speeds, avoiding unnecessary vibration or jamming.

The needs of riders vary depending on the purpose and environment of their riding. For example, mountain bikers may frequently use large gears to cope with different slopes on uneven mountain roads, while road riders prefer to use smaller gears to maintain higher speeds. The precise adjustment of the rear derailleur allows riders to quickly adapt to these needs.

Bicycle Rear Derailleurs can also play a certain protective role. When the chain is in a larger or smaller gear, it is less likely to be damaged by being too tight or too loose. In addition, the design of the rear derailleur usually ensures that the chain is transmitted more smoothly between the cassette gears, reducing friction and wear, and extending the service life of the various transmission components of the bicycle.