Eccentric bottom bracket bearing change

Changing the eccentric bottom bracket bearings is advanced service work. It means removing the rear wheel, releasing the shift cable, removing the crank, opening the eccentric bottom bracket, replacing the bearings, and then reassembling the drivetrain and checking tension and shifting. If you are not equipped and confident for every step, have it done by us or a bicycle workshop.

Applies to

The eccentric bottom bracket is the same on all Booda frames, but the rear wheel and shift cable steps below are written for the Shimano Alfine models (Banker, Hiker). On other models, remove the rear wheel as described for your hub.

Tools and parts needed

• 15 mm wrench
• 10 mm Allen key
• 4 mm Allen key
• torque wrench
• hammer
• straight wooden plank
• new eccentric bottom bracket bearings
• bearing adhesive

Before you start

Before removing the eccentric bottom bracket, mark the position of the non-drive-side eccentric bottom bracket cap against the frame. This lets you return the eccentric to the same position during reassembly, so that the belt tension stays as it was.

Step 1: Remove the rear wheel

1. Shift to the highest gear.
2. Turn the shift unit at the hub clockwise to loosen the shift cable.
3. Unhook the cable fixing bolt from the shift unit.
4. Loosen the axle nuts on both sides with a 15 mm wrench.
5. Remove the rear wheel.
6. Pull the cable out of the cable hook on the shift unit.

The same steps with pictures: Rear wheel removal with Shimano Alfine.

Caution

Keep the belt clean and do not twist or kink it. Do not force the wheel out while the belt, cable or axle is still under tension.

Step 2: Remove the crank

1. Loosen the drive-side crank axle bolt with a 10 mm Allen key. It is tightened to a high torque at the factory.
2. Remove the drive-side crank arm together with the spacer.
3. Pull out the non-drive-side crank arm with the axle.
4. If it is tight, move it gently while pulling.

Step 3: Open the eccentric bottom bracket

1. Loosen the 3 bolts on the non-drive-side eccentric bottom bracket cap with a 4 mm Allen key.
2. Remove the 3 bolts.
3. Remove the non-drive-side cap.
4. Remove the inner plastic tube.
5. Remove the drive-side cap.
6. Remove the dust caps from the eccentric bottom bracket bearings.

Step 4: Remove the old bearings

1. Knock out the old bearings from the inner side of each cap.
2. Clean the bearing seats before installing the new bearings.

Caution

Do not reuse damaged bearings. If the caps, bearing seats, dust covers or crank axle are damaged, stop and contact us.

Step 5: Install the new bearings

1. Apply bearing adhesive to the inner surface of both eccentric bottom bracket caps.
2. Push the dust covers into the new bearings.
3. Insert the new bearings evenly into their places.
4. Place a straight wooden plank on the bearing with the dust cover installed.
5. Strike the plank with a hammer until the bearing is fully seated.
6. Check that the bearing and dust cover are fully parallel and level.
7. Make sure the dust cover is level with the top of the eccentric.

Caution

The bearing must sit fully and evenly in the cap. If it is tilted, not fully seated, or not level with the dust cover, do not continue with reassembly.

Step 6: Reassemble the eccentric bottom bracket

1. Place the inner plastic tube into the drive-side cap.
2. Insert the drive-side cap with the tube first.
3. Insert the non-drive-side cap.
4. Refit the 3 bolts.
5. Turn the caps until the marks you made before disassembly line up again.
6. Tighten the 3 bolts with a 4 mm Allen key to a maximum of 5 Nm.

Step 7: Refit the crank

1. Insert the non-drive-side crank arm with the axle into the bottom bracket.
2. Make sure the wave spring washer sits on the non-drive side.
3. Place the spacer onto the axle from the drive side.
4. Refit the drive-side crank arm.
5. Tighten the drive-side crank axle bolt with a 10 mm Allen key and a torque wrench, to the torque specified for the crank fitted to your bike.

Caution

The crank bolt torque depends on the crank. If you do not know the correct value for your crank, do not guess: contact us, or have this step done by a workshop. A crank bolt that is too loose can come undone; one that is too tight can damage the thread.

Step 8: Refit the rear wheel

1. Place the rear wheel into the frame.
2. Lay the belt onto the front and rear sprockets by hand. Never lever it on.
3. Seat the axle fully in the dropouts.
4. Check that the belt sits correctly on both sprockets.
5. Tighten the axle nuts with a 15 mm wrench.

Step 9: Reconnect and adjust the shift cable

1. Hook the cable back into the shift unit.
2. Turn the shift unit clockwise.
3. Put the cable fixing bolt back into place.
4. Check that the yellow setting marks on the shift unit line up in the reference gear Shimano specifies for your hub version (8- or 11-speed).
5. If they do not line up, move the shift unit anticlockwise to tighten the cable, and let the cable hook settle into place.
6. If they still do not line up, adjust the cable with the fine-adjustment bolt on the shifter.

If the marks will not line up, or you are not sure which gear to check them in, have the shift adjustment done by us or a workshop before riding.

Final safety check

Before riding, check all of the following:

• The eccentric bottom bracket caps are aligned with the original marks.
• The eccentric bottom bracket bolts are tightened to a maximum of 5 Nm.
• The crank bolt is tightened to the torque specified for your crank.
• The belt tension is in the green range: see Belt tension.
• The belt runs straight after 10–15 crank turns: see Belt alignment.
• The rear wheel is fully seated in the dropouts.
• The shift cable is connected correctly and the yellow marks line up.
• The crank turns smoothly without grinding, wobble or side play.
• The bike shifts correctly while stationary and during a careful test ride.

Caution

Do not ride the bike if the crank has play, the belt is not seated correctly, the rear wheel is not secure, or the bike does not shift correctly.