E-Bike Shifters Decoded!

If you rewind the clock on the history of the bicycle, you will notice that their evolution has been mind-blowing. In the 80s, for example, we had the old Stranger Things “chopper” style bike with a big gear shifter on the top tube. Today, you push a button on your handlebar, and your gears buzz into place. Like many avid riders, you may be wondering how the voodoo of electronic bike shifters works.

Electric bike shifters use digital signals transmitted either by wire or Bluetooth to the relevant derailleur. The signal is then interpreted by the derailleur into a command, which shifts the derailleur by a preset amount. This shift pushes or pulls the chain up or down the gear cassette.

Understandably, many riders have some fair concerns or questions about electric shifters, like, “What happens if the battery dies?” or, “How reliable are they, really?” Hopefully, we can pedal through some of these questions and help you get to grips with the magic behind electric shifters. In fact, they could even be the perfect shifters for you.

The Basics Of Bike Shifters

In principle, electric bike shifters do the same job as mechanical shifters do, so you need to have a good grasp on how bike gears work to fully appreciate the beauty of electric shifters.

Almost every bicycle has a set of gears attached to the rear wheel, known as the cassette. These are the teethed rings that your chain pulls on to make the bike move. To avoid turning this into a mechanical engineering post, we’ll just cover the fundamental principles you must understand.

The biggest gear offers the most leverage (like a very long seesaw), so it requires the least effort from the rider to turn the wheel. The cost is that it doesn’t move the bike as far per pedal stroke. This makes it great for climbing.

Conversely, the smallest gear is the smallest lever, so it moves the bike quite far per pedal stroke but with greater effort from the rider.

The bike has a derailleur, which guides the chain onto the chosen gear ring, which switches between these gears. With mechanical shifters, this derailleur is connected to gear shifters on the handlebar with a thin cable.

The cable runs on a spring-loaded spool inside the shifter, and when the shifter is pushed, it either adds or takes away tension on the cable. This pulls the derailleur or releases it incrementally, which changes the position of the chain from one gear ring to the next.

In many cases, the gear on the back wheel is paired with bigger gear, or chainrings, attached to the axle of the pedals. These act like high- and low-range selectors in some trucks, effectively multiplying the number of gears. Like the rear gears, the chainrings also use a derailleur and a tensioned cable to shift the chain.

Electric Bike Shifters Replace The Cables

If you were to oversimplify the difference between mechanical bike shifters and electric shifters, you would say that they simply replace a mechanical cable with an electronic signal.

In other words, instead of a physical cable adding or releasing tension, there is either a wire or a Bluetooth receiver that transmits a digital signal between the signal and the derailleur. This signal comes as a specific command that tells the derailleur precisely how much it needs to shift and in which direction.

By removing the cables, you remove one of the biggest problems of mechanical shifters. There are few things as satisfying as the snappy response of a brand-new shifter cable, but that feeling doesn’t last very long. Cables stretch surprisingly quickly, and as they do, fine-tuning the derailleur becomes necessary and often frustrating.

Gears start to slip or skip as the cable becomes unable to keep up with riders’ inputs, and that can lead to an extremely frustrating experience.

Unlike these cables, the Bluetooth or electrical signal doesn’t stretch or deteriorate and will always be precise.

Electric Bike Shifters Use Motors That Are Ultra Precise

Once the signal from the shifter reaches the derailleur, it is interpreted by a small motor that moves the derailleur. This means that the derailleur is held in place by a motor and not by the waning tension of a cable. It also means that the shifts are near instant and practically perfectly precise every single time.

Most electric bike shifters don’t even require the rider to pedal the bike for the gears to shift. You simply hit the button, the signal goes to the motor, and the gears shift instantly.

In fact, some shifters, like the Shimano Di2, take precision even further. A common gripe of mechanical shifters is that it can be challenging to align the front and rear gears. If you are on your smallest front gear and biggest rear gear, the chain is pulled at a weird angle, which causes it to rub against the front derailleur.

Shimano’s Di2 system automatically makes micro-adjustments to the front derailleur to compensate for these tolerances, leaving you to just focus on pedaling.

Electric Bike Shifters Use Batteries

One of the perceived downsides of electric bike shifters is that they obviously use batteries to power the whole system. Most skeptics fear the moment that those batteries run dry, leaving you pedaling a single-speed bike all the way home.

If the shifters are wireless, they use a separate battery on each component. But if it is wired, it generally uses a central battery to power the whole thing. So, when the shifter is clicked, the battery gives a shot of power, which sends the signal back to the battery, which in turn figures out to which component it needs to send power to enact the command.

Fortunately, the work these batteries do is minuscule, and a single charge will last you somewhere between 15 and 60 hours of riding. Most weekend riders will likely charge their batteries quarterly, and if those batteries die, it’s because they typically last so long that the rider completely forgot to charge them.

Here is a good video that explains precisely how an electric bike shifter works:

Conclusion

Electric bike shifters work similarly to mechanical shifters in that a derailleur moves the chain onto the chosen gear. However, unlike mechanical shifters, electric shifters use a digital signal and precise motors to change the position of the derailleur, which makes shifting gears effortless and instantaneous.

Author

  • Miles Baxter

    Miles Baxter is an engineer with a longstanding love for bicycles, sparked by winning a mountain bike in a childhood lottery. Balancing a keen interest in mechanics with the thrill of biking, his career is a testament to the art of turning wheels and gears into adventures.

    Baxter Miles