Derailleur gears

At some point, before anyone purchases a bicycle or e-bike, one question inevitably comes up: derailleur gears or hub gears? The derailleur is a light, inexpensive gear system with high efficiency. Unlike with hub gears, most of the components of the derailleur gear system are exposed. A high-quality gear system is important for safe cycling and a pleasant riding experience.

What is a derailleur?

Derailleur gears are one of the most common types of gear shifting systems used on bicycles. In this system, a shift lever operates a derailleur that controls the course of the chain over the chainrings. With this system, the rider can only change gears while pedalling forward.

Derailleur shifting systems must be serviced regularly: Almost all of the moving parts are completely exposed, so the components are more vulnerable to dirt, weather conditions and damage from falls than those of some other systems, such as hub gears. That said, the maintenance they need is fairly trivial – only hub gears have lower maintenance needs. Replacing a chainring or the sprockets of the derailleur is a fairly simple matter. Unlike bicycles with hub gears, derailleur gears are only available with a freewheel.


Advantages of derailleur gears

Disadvantages of derailleur gears

  • higher efficiency
  • low weight
  • allows fine-tuning of cycling behaviour
  • economical shifting system
  • higher wear
  • maintenance required
  • can only shift when pedalling forward

How does the derailleur work?

On a bicycle with derailleur gears, the chain runs over a number of different chainrings and sprockets. The rear derailleur is used to shift the chain from one sprocket to another at the rear wheel, thus changing gears. There are one to three chainrings at the front and up to twelve sprockets at the rear, where the shifting mechanism is. The combination of the number of chainrings and sprockets determines the number of gears the chain can change between. Using shift levers on the handlebars, the rider controls a front and rear derailleur to put the bicycle in the desired speed. 

The bicycle chain runs between the cogs and is transported from one chainring to the other by the front derailleur. A front derailleur pushes the chain sideways so that it either falls onto the next smaller chainring or is pressed against the outside of the next larger chainring, which then, as it is pulled forwards, jumps up to that chainring. Bicycles with derailleur gears generally have 10 to 30 speeds.

The teeth on the chainring and sprocket engage with the bicycle chain to move it. This engagement is what makes the gear shifting happen. By shifting, you change the gear ratio between the pedal crank and the rear wheel.

What is the gear ratio on a bicycle?

The gear ratio on a bicycle means the number of revolutions of the rear wheel when the crank completes one revolution. Riding in a high gear means choosing a higher gear ratio. This means that it takes fewer revolutions of the crank (pedalling movements) to move the rear wheel, although it also takes more energy (the resistance is greater). In low gear, the cyclist must pedal more, but each revolution takes less energy.

Pedalling makes the chainrings rotate, and the cogs at the rear of the bicycle acts as the sprocket. The chain rotates the sprocket by interlocking with the teeth of the sprocket and pulling it forward.  The number of these teeth determines the gear ratio, which is: the number of teeth on the chainring to the number on the sprocket.

What’s better: derailleur gears or hub gears?

Hub gears are considered to be an extremely reliable system. The gearbox is enclosed, so it is protected from outside influences, and that makes it very low maintenance. Additionally, it is very unusual for a chain to jump off a hub gear. The shifting process itself is simple and the amount of maintenance needed is low. This is why hub gears are quite popular among users of city bikes. But as you move out to areas with elevation, derailleur gears quickly become the better choice for their higher efficiency and capacity for fine-tuning.

Derailleur gears are commonly used for a wide variety of reasons: The low weight of the rear derailleur is attractive for use on road bikes, while its high efficiency makes it attractive for mountain bikes. Additionally, the number of gears is more critical for the sporty rider, and on this, the derailleur system has the advantage. 

Derailleur gears – FAQs