Gebla Rohbox reset, maintenance, and cable replacement

Warranty option

This issue may be covered by your Booda Bike 2-year warranty. Many common problems, however, can be fixed quickly with the troubleshooting steps below. We recommend trying these steps first, especially if the bike is otherwise safe to inspect.

If you would prefer to start a warranty request, or if you are unsure whether the issue is safe to handle yourself, contact Booda Bike service and we will be happy to help.

Learn more

The Gebla Rohbox is an adapter that allows Shimano GRX brake/shift levers to operate a Rohloff gear hub. If the system shifts poorly, the cable tension usually needs adjustment.

A cable that is too loose can cause missed shifts or no shift at all. A cable that is too tight can cause the hub to shift two gears at once. Open the Rohbox cover, check the internal plate position, and make small adjustments with the two cable tension screws until the mechanism sits in the correct middle position.

Caution

Do not ride the bike if the shifting is unreliable, stuck, skips gears, shifts two gears at once, or the hub does not engage the selected gear correctly. If the adjustment is unclear or the problem remains after resetting, contact Booda Bike service.

What is the Gebla Rohbox?

The Gebla Rohbox is a mechanical shifting adapter.

It is used when a bike has:

• Shimano GRX road-style brake/shift levers
• a Rohloff gear hub
• a cable-operated conversion between the two systems

The Rohbox converts the cable movement from the GRX lever into the correct movement needed to shift the Rohloff hub.

Because this system works with precise cable tension, small changes in cable tension can affect shifting quality.

Applies to

This guide applies to Booda bikes equipped with a Gebla Rohbox shifting system, typically on models using Shimano GRX levers with Rohloff hub shifting.

Maintenance

Basic Gebla Rohbox maintenance:

• periodically check whether shifting still feels precise
• check whether cable tension has changed
• check that the cover screws and the large center screw are secure
• keep the outside of the unit clean from dirt and moisture
• inspect the cables and housing for wear, fraying, or drag
• readjust the system if shifting becomes slow, inaccurate, or inconsistent

If the bike starts missing shifts or shifting twice, check the cable tension before assuming there is a larger hub problem.

Common problems

These are the most common Gebla Rohbox issues:

• the cable tension loosens over time
• the adjustment screws are in a tight, hard-to-reach position
• if the cable is too loose, the bike may not shift correctly
• if the cable is too tight, the bike may shift two gears at once
• the shifter lever may need too much travel before the shift happens
• the mechanism may rub internally if the tension is too high
• a loose screw can create play in the mechanism

Before you start

The Gebla Rohbox is sensitive to cable tension. Make only small adjustments.

After every adjustment, test the shifting before making another change.

Resetting the Gebla Rohbox

1. Remove the cover

Use a T25 Torx key to remove the two screws holding the cover plate.

Then remove the large center screw.

2. Check the internal plate position

Inspect the position of the internal plate.

The middle gear drives the shifting mechanism:

• when shifting down, the mechanism rotates the gear in one direction
• when shifting up, the mechanism rotates the gear in the other direction

The goal is to return the mechanism to the correct centered position.

3. Identify the two cable tension screws

Two cables enter the Gebla Rohbox:

• one cable is responsible for downshifting
• one cable is responsible for upshifting

Both cables have a tension screw. Use these screws to loosen or tighten the cable tension.

4. Adjust the cable tension

Make small adjustments only.

Use the diagram above as a reference:

Adjustment state	What it means
Too loose	The shifter lever must travel too far, and the bike may not shift correctly.
Correct	The mechanism sits in the correct middle position and shifts cleanly.
Too tight	The mechanism can rub against the gear, and the bike may shift two gears at once.

5. Test the shifting

Before closing the Rohbox:

1. Shift up and down through the gears.
2. Check that the mechanism moves freely.
3. Check that the shifter does not need excessive lever travel.
4. Check that the mechanism does not rub or bind.
5. Confirm that one lever movement gives one clean gear change at the hub.

6. Reinstall the cover

Once the shifting feels correct, reinstall the cover plate and tighten the screws.

Tightening the screws

If the system feels loose or the cover has play:

1. Remove the cover.
2. Check the large center screw.
3. Check the cover screws.
4. Tighten the screws securely.
5. Recheck shifting after reassembly.

Note

The screws are in a relatively tight area, so access can be awkward. Work slowly and avoid forcing the tool at an angle.

Cable replacement

The Gebla Rohbox uses two shift cables. Cable condition has a direct effect on shifting accuracy.

When to replace the cable

Replace the cable or housing if:

• the cable is frayed
• shifting becomes heavy or sticky
• cable tension no longer stays stable
• the housing is damaged or contaminated
• the system cannot be adjusted reliably anymore

Final check

Before riding, confirm that:

• the Rohbox cover is secured
• the large center screw is secure
• both cables are seated correctly
• the bike shifts up and down reliably
• the hub engages properly in the selected gear
• one lever movement causes one clean gear change

Caution

If the bike skips gears, does not engage a gear, shifts two gears at once, or the shifter feels blocked, do not ride the bike. Contact Booda Bike service.

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