Converting a mountain bike to electric is one of the best-value routes into e-biking you keep a frame you love and add electric assist for a fraction of the cost of a new e-bike. This guide covers the UK conversion process in 2026.
What You Need for a Bafang Mid-Drive Conversion
- Mid-drive motor kit (most popular: Bafang BBS02B 750W or BBSHD 1000W) includes motor, controller, display, throttle, PAS sensor, brake sensors
- Battery most popular: 48V Hailong downtube or Reention Eel shark pack. 10-17.5Ah for most trail use
- Tools BB tool for your shell type, torque wrench, cable housing cutters
- Bafang BBSHD 1000W Review
- TSDZ2 Torque-Sensing Mid-Drive Review
- Which Bikes Are Bafang Compatible?
- E-Bike Battery Buying Guide UK
- E-Bike Maintenance Guide UK
Is My Frame Compatible
Bafang BBS-series kits require a threaded (BSA) bottom bracket shell. Sizes: 68mm (most UK hardtails), 73mm (many full-suspension frames), 100mm (fat bikes). Press-fit BB shells (PF30, BB86, BB92) are NOT directly compatible. Check our Bafang compatibility guide before ordering.
Step-by-Step Conversion Process
Step 1: Remove your existing bottom bracket using the appropriate BB tool.
Step 2: Thread the Bafang motor unit into the BB shell. Apply grease to the threads. Torque to spec (usually 40-50 Nm).
Step 3: Refit the chainring. Use the supplied Bafang chainring do NOT use your old road/MTB chainring directly.
Step 4: Route the controller (typically mounts on the downtube). Route motor cable to controller.
Step 5: Mount the battery. Hailong packs use a bottle cage-style mount. Reention packs use a slide-in mount.
Step 6: Install display and controls. Display on handlebar. PAS sensor at the BB shell. Brake sensors clip to existing brake levers.
Step 7: First test. Check all power modes, confirm PAS sensor is reading correctly, test brake cutoff. Keep the first ride slow.
Is a Converted Bike Road Legal
A Bafang BBS01B (250W) conversion can be configured as an EAPC road-legal e-bike if the motor is set to 250W max and PAS cut-off is at 15.5 mph. A BBS02B or BBSHD at full power is NOT road legal as an EAPC. See our full electric bike law guide.
Buy the kit: Shop Bafang kits 48V Hailong Battery
More: BBS02 vs BBSHD comparison Bafang compatibility guide