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I need some guidance on how to replace the shifting cable on a Cube nuroad with its internal cable routing.

I prefer not to replace the outer cables nor to remove the hydraulic hose.

The hydraulic brake hose and the rear shifter cable are routed internally.

I have a partial idea on how it's implemented.

What I know so far:

  1. The plastic inlet/outlet part consists of two parts which clamp the cables, they're pulled together with the screw
  2. The shifter cable ends/terminates in the top inlet and terminates at the bottom inlet
  3. The actual shifting (inner) cable is lose inside
    • I can see the end cap in the inlet
    • I hear it rattling against the frame tube when pulling and pushing the cable
  4. The hydraulic hose is fed through the opening and exits at the bottom opening
    • it's not terminated
    • it's not fixated

This is how the inlets/outlets look like:

Top inlet/outlet Bottom inlet/outlet


This is how I imagine replacing the cable ...

Needed:

  1. Two ~1.2mm diameter shrinking tube (~10 cm) for splicing cables
  2. Lighter, heat gun or torch
  3. ~1.5m long, ~1.2mm diameter junk shifting cable, electrician wire or cord to help pulling the new cable through the frame

Process:

  1. Cut the cable at the derailleur
  2. Push the cable from the derailleur end to give the assembly some play
  3. Loosen the top and bottom inlet screw, remove the outer part and pull out the inner part
    • ensure the inner clamp part does not get lost inside the tube
  4. Pull out the outer cable from the bottom clamp
    • the inner cable should now hang out of the bottom clamp
    • the outer cable from the bottom outlet to the derailleur is empty
  5. Pull the inner cable out of the clamp
    • it is now only fed through the top clamp and through the tube
  6. Splice the installed cable with the helper cable
  7. Pull the outer cable slightly out of the top clamp
  8. Pull the spliced cable carefully out of the top inlet, don't have it disappear inside the tube
  9. Fixate the helper cable at the frame
  10. Open the splicing and remove the shrinking tube
  11. Pull the inner cable from the shifter
  12. Feed the new inner cable through the shifter and outer cable
  13. Feed the new inner cable through the top end cap and clamp
  14. Splice the new inner cable with the helper cable
  15. Unfixate the helper cable
  16. Pull the spliced cable from the bottom opening
  17. Open the splicing and remove the shrinking tube
  18. Feed the new inner cable through the bottom clamp into the outer cable to the derailleur
  19. Mount the bottom clamp
  20. Mount the top clamp

Splicing would look like this:

Spliced cable

... which is quite sturdy.


I'm not sure about the clamp mechanism and the internal cable route. Would there be some guide or are the hydraulic hose and the inner cable going in a straight line?

Is there something missing in the process or can steps be skipped/simplified?

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  • 2
    Do you have cable liner? You could slide cable liner up the old cable to act as a guide through the frame for the new cable.
    – Michael
    Sep 4 at 21:10
  • No, I don't have cable liner at hand. Sep 4 at 21:12
  • By the way: Isn’t it dangerous to have an uncovered cable running along the hydraulic brake lines? It’s only the rear brake but still dangerous in case it rubs through …
    – Michael
    Sep 5 at 6:24
  • There might be an installed liner (I did not have the whole thing apart yet). And whether it rubs nor not probably depends on the routing. I doesn't have to be the case that it crosses and touches. Sep 5 at 6:35
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I've done something similar when replacing the outer and inner of a full-length internally-routed cable. My method was:

  1. Have a new inner and outer cable to hand.
  2. Cleanly cut the end of the old inner cable, and clean. Ideally it should not be rusty.
  3. Attach the end of the new inner cable to the old inner cable. Tape won't work - I first did a butt-joint with superglue, but that wasn't good enough.
    Second was to trim some strands from each end, and overlap/intertwine the remaining strands and apply superglue/CA glue, and leave it to cure overnight.
  4. Then I could push the new cable in, and the old cable was encouraged to go backward.
    This leaves you with a new cable installed backward, hanging bare inside the frame.
  5. Cut the outer cable to just over the finished length, clean the ends, but don't fit ferrules.
  6. Then fit the new outer onto the end of the new inner and push it through the frame. You might need lubricant. The inner cable is purely there as a guide, you can't pull the outer into place.
  7. Once the new outer is through, you can whip out the new backwards inner, install the ferrules, and then feed it through normally. Trim to length and finish the job.

If you drop the cable inside the frame, then it gets much harder, specially if the access ports are small. Sewing Cotton and an air blower become helpful.

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Take a piece of shift housing that's about 6cm longer approximately than the frame member it's run through, or about maybe about 800mm if you want a long one that can do pretty much anything. With a razor, carefully cut one long slit from end to end. With gloves and eye protection, whip it hard against a hard surface. It will come apart into a bunch of sharp wires and a liner. That's your liner. Cut the anchored part of the old shift cable so you have a clean end. Run the liner over the clean end. About 5cm from the end of the cable, put a big kink in it, ie bend it 90 degrees. That will keep the liner on as you feed the liner all the way through. Once it's through, pull the old cable out and slide the new one through.

Liners taken from housing are often the simplest approach because there are many kinds of frame ports and pieces that can fit something their size but no bigger. Some would accommodate the kind of splicing you proposed, and that's fine if so, but many will not.

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