Bottom Bracket Exchange

Bafang Bottom Bracket with Torque Sensor (120mm)

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NOTE: Working on the bottom bracket unit with torque sensor is critical – if you don't know, what you're doing, you may cause irreparable damage to the bottom bracket unit by ripping of the sensor cable.

  1. The silver ring screw clamps the chain wheel to this inner splined piece, which is inside the right side screw (left in the picture).
  2. The splined piece serves as an adapter between the main torque sensor unit (the central piece with shaft and splines) and the chain wheel.
  3. All three pieces have splines that only fit together in one rotational position, as one of the splines is wider than the others.


The specific tools you need are the following:

  • Pedal Arm / Crankset Extractor (to take off the pedal arms and pedals) Here's how: https://www.youtube.com/watch?v=IGnbl6v3esQ&feature=youtu.be
  • Bottom Bracket Splined Key (for the Silver Ring Screw) It has an inverted thread, the arrow on it points in the direction for tightening it.
  • Bottom Bracket Wrench Key (for the outer Main Screws) One side has an inverted thread, the arrow on them points in the direction for tightening them.

Short mounting instruction:

  1. left bottom bracket screw / sleeve (see Bottom Bracket Main Screws) mount first in the frame and tighten. First by hand until it goes no further, then by wrench: direction of rotation + torque is inscribed on the part itself.
  2. Screw in the inner part of this sleeve slightly, do not tighten it completely yet.
  3. Insert bottom bracket with sensor unit from the right side into the frame, first thread the cable (through the hole from bottom bracket into controller housing) and position carefully so that it is not squeezed. Make sure it is completely seated in the frame, if necessary, use a rubber mallet to help it along. Then tighten right sleeve, first again by hand, then with wrench: direction of rotation + torque is also on the part itself.
  4. Now check the sluggishness of the bottom bracket with the help of a crank arm and adjust accordingly with the inner part screw from point 2 – a special wrench is used for this.

Dismounting the bottom bracket sensor unit:

  1. To disassemble, carry out the steps in reverse.
  2. CAUTION: the bottom bracket itself must not rotate during (dis)assembly, otherwise the sensor cable will be damaged or destroyed / torn off! No guarantee or warranty in case of defect!

Controller housing lid

Pin Assignment:

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