Step-by-step guide to correctly replacing the inner tube of your NIEF electric FAT bike.
This chapter explains how to replace the inner tube of your FAT electric bicycle.
This technical operation was performed on the NieF APRUM model.
We recommend that any type of maintenance be carried out by specialized technicians.
It is important to use professional and high-quality materials.

To replace the inner tube of your electric bicycle, it is necessary to determine which inner tube to choose, the size is stated on the side of the tire. In our case, the tire measures 20×4.00″, so our inner tube will be 20×3/5-4.00″.
E.a. is also included in the technical specifications of each model.

What do you need to carry out this repair?

  1. Gloves
  2. Pair of scissors
  3. Inner tube 20 × 3.5-4.00
  4. Bicycle pump with analogue/digital pressure gauge
  5. 18mm torque wrench
  6. Allen key 4mm
  7. plastic cable ties

Step 1: work preparation

To perform the operation correctly and safely, it is recommended to remove the battery.
Place the bicycle on the ground as in the photo, note: display, speed switch and rear luggage rack.
It is recommended to place something on the floor that can protect the above parts. In this case we used soft plastic.

Motor connection and derailleur protection

Before removing the wheel, pay attention to the motor connector and derailleur protector.
A mudguard holder (right side) is also mounted for the NieF APRUM model.
Use scissors or a regular electrician's cutter to cut the plastic band. Be careful not to cut the engine cable or taillight cables.
A 4mm Allen key is required to remove the derailleur protector.
Place the removed parts on the workbench.

Check Bafang motor spacer ring

Check that the motor spacer is positioned correctly. They should only be installed in this direction. It is recommended to take a photo with your smartphone for the next steps.

Remove the locknuts from the motor shaft

Use an 18mm wrench and remove the motor locknut on the shaft.

Turn counterclockwise
Tighten: clockwise

After removing the lock nuts, the rear wheel can be removed.

Remove Fat Band

Removing a FAT tire is no different than other types of tires, on the contrary, its width makes it easier. It is also possible to remove the tire without using tire levers.
The video shows how to remove the tire without using a tire lever.


Always inspect the tire on the tread and on the inside.
It often happens that you find a glass splinter in the tire, and after replacing the inner tube, you cycle 1 to 2 km and the tire is punctured again.
In most cases there are residues on the inside of the tire.
To check the tire on the inside, it is wise to use gloves to avoid the risk of injury.

Discovering the problem

On the profile we discovered that an iron pin has made 3 holes in our inner tube.
In this case it is always advisable to replace the inner tube.
For a quick repair on the road, using the inner tube repair kit is also great. Don't forget to replace the inner tube as soon as possible.

Tire rolling direction

Always check the correct rolling direction of the tire (it is stated on the side).

Fitting tires and inner tubes

In this video we show how to install a FAT tire and inner tube at the same time. Pay attention to the correct rolling direction of the tire.

For bicycles with a thin tire, installation can also be carried out according to the classic method (outer and inner tube separately).

Check engine spacers and lock nuts

Check that the rear wheel is mounted correctly.
The axle must fit correctly into the dropout. The spacers should only be installed in this way (photos n.1 and n.2).

Check that the brake disc and chain are positioned correctly.

Tighten the hex nut

Once the rear wheel is properly mounted, tightening the lock nuts can begin. Use an 18 mm torque wrench and tighten to a maximum of 40 Nm.
If you do not have a torque wrench at your disposal, try to tighten properly without overloading, as this can damage the threads on the shaft, or in the worst case, break the shaft.

Motor connector

After mounting the rear wheel, derailleur protection and mudguard holder, we can connect the motor connector.
There is a small arrow on the motor connector and on the connector coming from the control unit. For correct installation, the 2 arrows must be mirror images of each other.

Last step

Connect the motor plug (for the APRUM model) and secure the taillight cables with a plastic cable tie.

Inflate the tire to the correct tire pressure.
NieF Aprum for use on asphalt and cycle paths: 1.3 Bar front - 1.7 Bar rear.
NieF APRUM for use on sand and in terrain: 0.8 Bar front - 1.2 Bar rear.