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

• higher efficiency

• low weight

• allows fine-tuning of cycling behaviour

• economical shifting system

Disadvantages of derailleur gears

• 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. 

How do I shift gears with a derailleur?

With a derailleur, you can only shift gears when you are pedalling. But until the chain is resting securely on the gear teeth, you should only pedal lightly. Once the shifting action is complete, you can pedal harder again.

What is the difference between hub gears and derailleur gears?

The components of a hub gear are assembled inside a hub on the rear wheel, so they are not exposed on the outside of the wheel. This means that hub gears are protected from external influences such as moisture, dirt, and impacts from falling. Derailleur gears are not internal, so their components are exposed on the outside of the bicycle. Hub gears are heavier, but you can shift them while standing still. With derailleur gears, you must be pedalling to change gears. Hub gears generally have from three to eleven speeds, while derailleur gears have as many as thirty. Derailleur gears are cheaper and can be fine-tuned to the individual rider, riding conditions, etc.

What is better for an e-bike: hub gears or derailleur gears?

Hub gears are reliable and require little maintenance; they are protected and therefore resist mud, moisture, and even falls better than derailleurs. Derailleur gears, on the other hand, can handle the highest torques and can be combined with the more powerful motors. This means that for sports pedelecs in particular, derailleur gears may be a better choice. The bottom line is that the choice between hub gears and derailleur gears really comes down to the specific use of the bicycle.

Many top manufacturers, such as Shimano, produce derailleur systems for e-bikes.

How do I shift gears with a derailleur system?

When shifting gears with a derailleur system, you have to pedal. However, you should only pedal lightly until the chain rests cleanly on the teeth. Only then do you increase the pressure again.

What is the difference between hub gears and derailleur gears?

The components of a gear hub are installed in a hub on the rear wheel and are therefore not exposed on the bike. Gear hubs are therefore protected from external influences such as moisture, dirt and falls. Derailleur gears, on the other hand, are open. Hub gears are heavier, but you can shift them when stationary. With derailleur gears, you change gear while pedaling. Hub gears have an average of three to eleven gears, derailleur gears up to 30. Derailleur gears are cheaper and can be more finely tuned to the riding behavior.

Which is better: derailleur gears or hub gears?

Gear hubs are considered to be particularly reliable. The gearbox is protected, making it very low-maintenance. In addition, the chain rarely jumps off a hub gear. The shifting process itself is uncomplicated and requires little maintenance. This is why hub gears are particularly popular with users of city bikes. However, as soon as you head into mountainous regions, derailleur gears with their high efficiency and fine tuning are often the better choice.

Derailleur gears are popular for various reasons: The low weight of the rear derailleur makes them interesting for racing bikes, while they are installed on mountain bikes because of their high efficiency. The number of gears is also often decisive for sporty riding: derailleur gears have a clear advantage here.