The Transmission System of Electric bike: Derailleurs and Hub Gears

Do you need clarification about the pros and cons of derailleurs and hub gears? We demystify all of them below. Many e-bike presentations focus on the motor's performance or the battery's size. The drive train of an electric bicycle is an often overlooked element. The extra power of an electric bike's motor allows for larger, more efficient gears.

 ebike derailleur gears

About derailleurs and hub gears

What is derailleur gearing? This set consists of a black derailleur, or rear mechanism, and a rear cassette, or rear cog, a row of silver sprockets. Some bikes also use a front derailleur, but front derailleurs are rare on e-bikes.

The derailleur gears are external, and the rear derailleur is usually connected to a cable. The derailleur guides the chain to a larger, easier-to-pedal sprocket, ideal for hill climbs, by tightening the thread with the lever on the handlebars. Releasing the tension in the cable means that the springs in the derailleur pull the chain down and out onto the more minor, harder-to-pedal cog sprockets (higher gears) for higher-speed riding.

Most e-bikes come with a derailleur, but hubs are also the primary option. Both options go back many years, so they are technologically advanced and should serve their purpose well. So what are the advantages and inconveniences of these two devices?

Pros of derailleur gears:

  • The main advantage of a front derailleur drivetrain is its quick response to shifting commands. The rider can instantly change gears while pedaling by activating a selector on the handlebar.
  • The presence of the electric motor also accelerates the responsiveness of the chain's movement on the sprockets.
  • Derailleur shifting is also reliable on e-bikes, especially e-bikes with electric crank motors; it tends to wear out more than conventional bikes.
  • They are lightweight systems, in the budget end of the market, and if damaged, are cheap and easy to replace. It is said to be more efficient than internal hub gears.
  • The derailleur offers a wide selection of gear. Adding more color to that point: In recent decades, a relatively simple wide-range gearing has been developed that uses only a single sprocket on the front of the chain and a vast range of cogs on the rear cassette.
  • The number of teeth is usually given in the derailleur gear specification.This setup means "low gearing" - i.e., easy pedaling on more resistance off-road, and you could tackle steep terrains. Note that fewer teeth on the front sprocket make the bike easier to ride, while the larger rear derailleur sprockets make pedaling easier. In contrast, a gear setup for a typical city bike might have a front sprocket and rear cassette, offering a narrower, higher gear range for typical town riding environments.

Cons of derailleur gears:

  • Changing gears while stationary, or changing multiple gears in one shift is not recommended.
  • Due to the open design, they require regular cleaning and maintenance as the open elements get dirty quickly thus making the gear noisy and difficult to move.
  • The derailleur sticks out close to the ground, so it's also prone to damage. Although it usually takes a hard impact to cause harm, it shouldn't happen very often.
  • More significant wear (about 30% higher than on a standard bike) is due to the motor's forceful pull on the chain for pedaling assistance. It means the bike's chain and sprockets must be checked more frequently and possibly replaced.

All that said, they are relatively easy to maintain for the user compared to hub gears.

Hub gear:

The hub gears are entirely wrapped in the rear hub. A hub gear system consists of a corner and integrated kits located on the bike's rear hub. Due to its location inside the seat, the gear system is well protected from external influences. That will prolong the life of gear hubs and minimize the risks of damage to equipment. The parts of the system is planetary gears, a hub gear, internal gear hub etc. The gears and greases are sealed within the housing of the hub gear, leaving the equipment and mechanism exposed to the elements in contrast to derailed kits. Changing gear ratios has traditionally been done with a hub-attached shift lever and Bowden cables, and twist-grip shifters have become common. The Shifting takes place inside the hub shell, and the pinions mesh together to make the rear wheel spin at a different speed than the sprocket. Hub gears are mechanically more complex than derailleurs, where the chain derails from one sprocket (or sprockets) to a larger or smaller sprocket, but the mechanism is hidden from rain and harsh and violent impacts; Shifting also doesn't depend on the state of the chain.

Pros of hub gears:

  • Low maintenance. Since the gears are not exposed to the elements, they can often run for thousands of miles at will without much attention. Your chain should also be more durable since it only moves between different gears sometimes.
  • It can shift multiple gears at once from a standstill, an ideal feature for stop-start riding around town. If you are looking for a belt-drive e-bike rather than a chain-drive e-bike, you will need a hub gear bike, as derailleurs are unavailable for belt drives. They are ideal for riding in all conditions as they are sealed from the elements.
  • The internally geared hub design also eliminates the need for cables and shift levers, making maintenance simpler, less frequent, and more affordable. The new gear system can be operated by an electric motor delivering up to 80Nm of torque to suit the broadest range of use cases, making it ideal for urban and hiking and heavy-duty cargo e-bikes.

Cons of hub gears:

  • Usually heavier and more expensive than derailleur gears, especially for systems with more kits. If something goes wrong inside the hub, it's usually the job of an expert (although this is very rare, because its reliability, on the other hand, is often a reason to choose hub gears).
  • You can opt for a ''rear pedal'' coaster or fully enclosed drum brakes with some hub gears, although these options are more common in continental Europe than in the UK and US.
  • Usually has a smaller range than wide-range derailleur systems. The rear wheel is more difficult to remove (for tire repairs, maintenance, etc.) than a derailleur system.


A derailleur or hub gear system

Which is better: A derailleur or hub gear system?

The internet is full of arguments about which is better - derailleurs or hub gears.

The answer is simple: it depends. It depends on how you ride and what derailleur or hub setup your e-bike is running.

As a general rule, hub gears, and cheaper narrow-range derailleurs are used on city bikes, and derailleur gears are used on more sport-oriented e-bikes, i.e., e-road bikes or off-road bikes.

So the conclusion is – you decide what's better for you. The derailleurs are very simple in use and the perfect solution that stood along the time. Throughout the centuries there was a lot of refinement and although it can be a little finicky and hands-on, they still work pretty well in most conditions and their prices are variable. They are easy to service and don't weigh too much. Internally geared hubs are the best way to avoid small everyday hassles on your bike. They are easy to use and very practical for everyday uses such as simple transportation from one point to another. Just make sure that you have shops nearby where someone can service or rebuild the hub if it's ever necessary.