Wiring a bicycle dynamo hub…through the fork vent hole

3 minute read

Being a sucker for a clean bike set up, I had always wanted to improve how my dynamo hub on my touring bike was hooked up. Originally on my Genesis I had the cable running down the outside of the fork, held on with zip ties. While it worked fairly well, the zip ties looked ugly and the cable housing was exposed to the elements (causing the rubber casing to harden and start to perish). I finally found the time to try and improve the wiring on my newer tourer, my Soma Double Cross. The vent holes in the fork provide a perfect route for the cable so that the majority of it is hidden safely inside the fork, away from the elements and things for it to get snagged on. It is however, incredibly difficult to pass the wire through! So firstly, if you're going to attempt to do so, you need a lot of patience. Here's how I did it.

Steps

  1. Cable passed through the forksGet a gear cable and bend the end slightly so it's curved.
  2. Feed the cable in through the vent in the crown (top end of the fork) so that it will come out at the bottom vent by the drop outs.
  3. Feed the cable in slowly, not forcing it if it becomes stuck as this can cause the cable to fray, then it definitely won't go through. Instead spin and twist the portion of cable you are feeding in (also moving it back and forwards). This causes the curved end of it to rotate and eventually get past any obstructions. I found around the middle of the fork quite tricky (possibly due to the low rider mounts on my Surly LHT forks).
  4. Eventually the cable will reach or pass the vent hole at the bottom of the forks. This is a tricky part. Once again you have to spin and twist the cable at the crown end. This will cause the curved tip to rotate and if you're luck line up with the vent hole so that you can push it through. I managed to do this 3 or 4 times so it is possible. Once done feed plenty of the cable through.
  5. Get some thread. I found it too difficult to attach my dynamo wire to the brake cable, hence using thread first.
  6. Fray the end of the brake cable slightly and pass some of the thread between the frayed cable. Make sure you wrap it around plenty of times so that it's held fairly securely.
  7. Now pull the cable back through and out where it started, taking the thread with it.
  8. You should now have a piece of thread running through your fork and the gear cable out and away from the bike.
  9. Using electrical pliers cut away a portion of the rubber housing on your dynamo wire, exposing the bare wire underneath. Wrap the thread between the individual bits of wire, bend them over, then twist them to ensure the thread is attached to it securely.
  10. Now gently feed the wire through the bike. The thread isn't very strong, so just use it as a guide. Push the wire in at the crown end. It's easier to finish at the lower vent as you can see it more easily (compared to the top vent). If you meet any obstructions.
  11. If all goes well, you should end up with a wire running inside your forks. It's not an easy thing to do, so will take quite a few attempts.

Additional Tips

  • The thinner the wire, the easier you'll find it to feed through, so get some high quality, nice and fine wire. I just used some spare wire I had lying around, so I don't know the exact gauge/spec. It was a bit of a tight squeeze getting it through the vent hole.
  • Grease the brake cable and wire to help them feed through more smoothly.
  • If you find yourself trying to force something through, it probably won't work. It's delicate work that requires precision, not force.

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