A magnet clipped to the wheel speed sensor fools the controller into thinking the wheel is turning slower. 10-min install, no tools. Sensitive to moisture.

BadassBox 5

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Internal wired kit

Plugs into the motor harness. Discreet, real speed shown, advanced features (Bluetooth, anti-detection). Requires opening the motor case.

SpeedBox · VOLspeed · PearTune · Wiesel

💻

Software flash

Reprogrammes motor firmware via PC cable. No hardware to install — invisible to service centres. Shimano EP801/EP6 only.

Eplus Flash

The basics

Why your ebike cuts out at 25 km/h (15.5 mph)

A magnet fixed to a spoke passes a sensor on every wheel rotation. The controller counts this frequency, multiplies it by the wheel circumference and calculates real speed. When it exceeds 25 km/h, it cuts motor assistance immediately.

It's not the motor that is limited — it's the controller choosing to stop powering it. Power remains intact (250W nominal). A tuning kit works by fooling this sensor: it sends a lower frequency than reality, and the controller thinks the bike is going slower than it is.

Internal kits (SpeedBox, PearTune, Wiesel…) splice into the controller harness and interpolate the signal. External kits (BadassBox) place an additional magnet on the original sensor to disrupt the reading. The software solution (Eplus Flash) directly reprogrammes the motor firmware — no physical component required.

The measurement circuit

Magnet on spoke

Passes the sensor on every wheel rotation

Speed sensor

Counts the magnet passing frequency

Controller

Calculates speed and cuts assist at 25 km/h

The kit acts here

Falsifies the signal sent to the controller

Motor power: unchanged

The kit does not modify the 250W motor output. It only removes the cut-off at 25 km/h. What changes: range decreases (air resistance scales with the square of speed).

Alternative method

Tuning without a kit: manual methods

Two techniques exist without buying a kit. They work on older motors (pre-Bosch 2011), but are ineffective or risky on modern systems with built-in software anti-tuning.

1. Move the sensor to the crank

The crank turns 2–3× slower than the rear wheel. By relocating the magnet to a pedal and the sensor opposite it, the controller receives a lower frequency — it believes the bike is going slower. Tools needed: Allen/Torx key and adhesive tape.

Result: the speedometer shows half the real speed. Easily reversible. Does not work on Bosch Gen 4+ or Shimano EP6/EP8.

2. Disconnect the sensor wiring

Removing the speed signal entirely zeros the speedo — assistance stays on permanently. Hard to target without accurate wiring diagrams. Difficult to reverse and may damage the controller on modern systems. Avoid on any motor made after 2015.

Limits of manual methods

!Ineffective on Bosch Gen4+ (software anti-tuning)

!Ineffective on Shimano EP6 / EP801

!No real speed shown on display

!Risk of error codes on connected systems

Motors compatible with manual method

Bosch (pre-2011)Possible

Bosch Gen 2, 3, 4, 5No

Yamaha PW (older)Possible

Yamaha PW-X, PW-X2, PW-X3No

Shimano EP6 / EP801No

Bafang mid-drivePossible

What concretely changes after tuning

Three points to consider before fitting a kit.

Range: −20 to −50%

Air resistance increases with the square of speed. Riding at 35 km/h instead of 25 km/h consumes 2 to 2.5× more energy per km. A 500 Wh battery giving 80 km at 25 km/h will only give 40–60 km at tuned speed.

Recommended modifications

Larger chainring: comfortable cadence at high speed

Tyre pressure +10%: reduces rolling resistance

Fork inspection: more stressed at 35–45 km/h

Hydraulic disc brakes: increased stopping distance

Warranty & insurance

Manufacturer warranty is voided from the moment a kit is fitted — even if removed, technicians can detect modification traces in motor logs. Ebike insurance does not cover accidents on a tuned bike.

Exception: software kits like Eplus Flash (firmware reprogramming) can be invisible if a reset is performed before a service visit.

Legality in the UK & Europe

Tuning an ebike reclassifies it as a moped (L1e category). On public roads: registration, insurance and helmet are mandatory — and the manufacturer warranty is voided. Under the Highway Act 1988, electric bikes must not provide assistance beyond 15.5 mph on public roads.

For road-legal 28 mph ebikes: Consider a factory S-Pedelec (speed pedelec) — registered and insured from the factory.

📋

Reclassification

Bike becomes a moped (L1e category).

🛡️

Insurance

Third-party liability required.

🪪

Registration

Number plate and V5C equivalent.

⛑️

Helmet

Approved motorcycle helmet required.

Which kit for your use case?

The right choice depends on terrain, discretion requirements and budget.

⛰️

Electric MTB

Wet terrain, vibrations — robust internal kit.

SpeedBox · BadassBox

🏙️

Urban commuter

Maximum daily discretion.

Wiesel

🤫

Total stealth

No-hardware or invisible solutions.

Wiesel · Eplus Flash

💷

Budget pick

Best performance per pound from £89.

Eplus Flash · SimpleK

⚙️

Shimano EP801 / EP6

Safe compatibility, E299 risk avoided.

Eplus Flash · PearTune 3.0

🛰️

DJI Avinox

Amflow, Moustache and 60+ OEM brands.

PearTune MSO 5.0 RC

Guides & tools

Frequently asked questions

Is ebike tuning legal in the UK?

No, not on public roads. Under the Highway Act 1988 and the Electrically Assisted Pedal Cycles (EAPC) Regulations, an electric bike must not assist beyond 15.5 mph (25 km/h). Fitting a tuning chip reclassifies the bike as a moped — requiring registration, insurance and a helmet on public roads. All use should be restricted to private land.

Which tuning kit should I choose for my motor?

SpeedBox and Wiesel cover most Bosch and Yamaha motors. PearTune 3.0 and Eplus Flash are the only safe options for Shimano EP801. PearTune MSO for DJI Avinox. Use our kit configurator for a 3-click answer.

Shimano EP801: which kits are truly compatible?

ONLY Eplus Flash (software, £89) or PearTune 3.0 (hardware, ~£175). SpeedBox, BadassBox, VOLspeed on EP801 = E295 error then E299 = permanent, irreversible motor lock.

Does a tuning kit damage the motor?

No. The kit does not modify power output (still 250W nominal) — it removes the cut-off at 25 km/h. Range decreases by 20–50% depending on speed (air resistance scales with v²). Manufacturer warranty is voided.

What is the difference between an external and internal kit?

External (BadassBox): clips to the wheel speed sensor — no cable cutting, 10-min install, fully removable. Shows half the real speed on the display. Internal (SpeedBox, PearTune, Wiesel): spliced into the motor harness — more involved but shows real speed and offers advanced features.

SpeedBox vs BadassBox — which is better?

BadassBox wins on ease of installation (no tools, 15 min) and leaves no trace in motor logs. SpeedBox wins on real speed display, broader motor compatibility and lifetime warranty. Use BadassBox if you frequently visit a dealer; SpeedBox if you want full data accuracy. See our full SpeedBox vs BadassBox comparison →

What happens if eBike Flow suggests a Bosch firmware update?

Do not accept without checking first. The 11.13.0 firmware (April 2024) bricked SpeedBox 1.0/1.1/1.2. Disable auto-updates in eBike Flow and verify compatibility with your kit manufacturer before accepting any update. Firmware guide →

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