Anyone who has sat on an e-bike knows the feeling: you pedal energetically and the bike accelerates powerfully, you easily reach 25 km/h — and then suddenly ride into sticky mud. At least that’s how it feels. At this speed a legal limit is reached and the bike turns off the juice. Sometimes this is pretty annoying, as the bike could do more. We’ve researched for you how to get round this restriction, and what you need to observe if doing so.

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Basic principle of e-tuning

An e-bike constantly monitors its speed and how powerfully the rider is pedalling. Using this information, it decides on how much drive to deliver. When the bike reaches the legally defined speed limit of 25 km/h, the motor support is deactivated. With the right fitness or gradient, the bike can of course still go faster — just without motor drive. If motor assistance above 25 km/h is desired, then the system must be made to think the current speed is slower than it actually is. Most tuning options are based on this point. A small electronic device is installed between the wheel magnet sensor and the computer unit, which calculates the speed. This device manipulates the electrical impulses from the magnet, and the computer then calculates these falsified signals into a slower current speed. As a consequence, the drive is not deactivated even though the bike is actually moving much faster than 25 km/h.

Faster – but not more powerful!

Many e-bikers assume that by installing an e-tuning kit, they get a more powerful motor which allows them to accelerate faster. Unfortunately, this is not the case. The tune doesn’t increase the performance of the drive unit; it just artificially circumnavigates the legal 25 km/h limit. Up to this speed no change is achieved, so handling on steep ascents remains exactly the same.

Increased loads for motor and battery

The question of whether the e-tuning puts increased loads on a system is easily answered: yes and no! The e-tuning doesn’t influence the motor control at all — motor RPM and temperature control remain unaffected. Thus, there is no danger of unintentionally overloading the manufacturer’s drive unit. However, by overcoming the 25 km/h limit, in practice the system is used at full load for much longer periods — comparable to long mountain climbs. The motor uses more electricity; the battery is drained faster and requires more frequent recharging. The higher battery temperatures don’t have an especially positive effect on its overall lifespan.
In addition, the rest of the bike’s drivetrain is worn out faster as the motor is used more and with higher loads applied to the chain than using a regulated motor that forces you to comfortably pedal along at 25 km/h.

So what does e-tuning actually achieve?

If you buy a tuning kit, you won’t be getting a new bike.
The adverts of some suppliers — suggesting speeds of up to 75 km/h — are theoretical in nature.
A tuned e-mtb with a normal 250 watt motor can briefly reach a top speed of 60 km/h with a lot of rider effort and on flat terrain. For longer periods, a fit amateur rider could achieve 35-50 km/h. Compared to a 25 km/h un-tuned bike, there can be a noticeable increase in riding fun, especially on flatter trails.

Nice side-effect: better training thanks to e-tuning

This might sound like a paradox at first, but it really is true: on a tuned bike most bikers ride with more human effort too! The 25 km/h limit has an unpleasant effect. Up to this limit, the bike always rides faster the harder you pedal. But once you’ve reached 25 km/h, the motor support is reduced until all additional propulsion comes from your own legs. Only after this do you accelerate completely from your own power. So at the 25 km/h limit the bike doesn’t go any faster for a time, even though you are pedalling harder and harder. This effect can feel pretty mean — especially when you don’t know the background reasons for it. This is also the reason why many e-bikers ride at exactly 25 km/h and don’t have to contribute much own effort. A tuned e-bike avoids this problem with an easy rule — pedal harder, go faster!

Legal, illegal, who cares?

E-bikes with pedal support of up to 25 km/h, a nominal motor power of 250 watts maximum, and a power assist of 6 km/h maximum are categorized legally as normal bicycles; the rider is not subject to any additional rules and regulations.
If the pedal support still functions above 25 km/h, then the bike becomes a so-called low-power bike. This needs an insurance number plate and must be registered. This last rule will above all make riding a tuned e-bike legally in public spaces as good as impossible. In theory, it is still possible to have a self-tuned e-bike registered, but in reality this would cost so much that you’d be better off buying a brand new, unrestricted e-bike. So if an e-bike is fitted with a tuning kit, you can only ride legally on private land.

Take note: many e-bike manufacturers are very critical regarding tuning kits and threaten users with the loss of their warranty. We would recommend clarifying with the manufacturer or retailer what is allowed and what isn’t.

The Tuning kits

Tuning kits are available in different versions from varying manufacturers. The main difference is in the way they are fitted. Most of them need to be soldered into a cable or plugged into the cable which connects to the wheel magnet sensor. To do this you need to cut the cable and sometimes take off the motor cover. These solutions cannot be spotted externally and can partially be turned on or off from a hidden switch or using the bar-mounted control unit.
Other tuning kits are just placed over the magnet sensor. You don’t need to cut cables, but the kit is easily visible.

We took a look at a few of the most common tuning kits:

Chiptuningbox from – 139 Euros


The Chiptuningbox is the simplest way to tune an e-bike which we could find. You just plug the plastic box over the magnet sensor and re-adjust the wheel-mounted magnet and you’re done. The whole thing takes a minute. Above 16 km/h, the box cuts a third of the speed communicated by the magnet to the control unit and therefore increases the drive support to a theoretical 75 km/h. To deactivate just remove the box – you don’t need to do anything to the cables or cable routing of the bike.

Sx2 Dongle from – 159 to 199 Euros


>With this option an additional cable is introduced to the e-bike cable loom. To activate the tuning function, a small stereo jack is then plugged in. Fitting requires the motor cover unit to be removed, but the electronics are as good as invisible afterwards. On the more expensive variant, the system can be turned on and off from the handlebar display.

JUM-Ped-SE Vmax Remover for BionX from – 169 Euros

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For BionX drives another solution is available: using a tuning tool which is directly connected to the handlebar display, the default 25 km/h limit can simply be de-activated. Afterwards, you just remove the tool. To reactivate the speed limit, reverse this process. Simple, quick and invisible — unfortunately only available for BionX so far.

ASA eSPEED for Bosch from – 179 Euros


Here an additional cable is introduced to the cable loom, similar to the Sx2 Dongle.
Fitting is a bit more time-consuming, but you have the advantage that the system delivers two different speed values to the display unit and motor controller. The correct speed limit stays displayed on the bar control unit, in contrast to the other systems.

Words: Tobias Döring Fotos: Christoph Bayer