Internally routed cables are more resistant to the weather and make the bike look neater. However, replacing internal gear cables on bike can be a tricky task. In time-honoured fashion, CMA will show you how to tackle the job in easy steps.
Some modern bike frames are designed to have the cables routed internally. This way of cable fitting protects it from the elements and makes the bike looks neater.
– With outer casing running through the frame.
– Without any outer casing running through the frame
Tools required
To make the task easier you will need:
- 5 mm allen key or 8/10mm spanner. They are used for releasing and tightening the cable on the derailleur pinch bolt.
- Cable cutters. They differ from pliers and snips as the blades cross over each other.
- 1.5mm allen key or a pin. Useful to prise the closed up P.T.F.E tubing.
- Spare outer casing and utility knife. The PTFE from inside the outer will be necessary when replacing gear cable without casing.
- Insulating tape. This to stop the cable sliding out.
Replacing internal gear cables on bike
If the casing is fitted internally, when replacing the inner wire it will act as a guide.
- Shift the gear lever to the highest gear at the back or the lowest gear at the front.
- Find the end of the cable where it is attached to the derailleur.
- Undo the retaining bolt just enough to remove the cable.
- Where it is fitted the cable will probably be flattened and maybe frayed. Cut off the damaged end so that it will be easier to remove.
- If required remove the cable from the bottom bracket cable provider or remove the provider itself.
- While holding the casing at the top pull the cable out of the outer.
- Holding the casing slide the new cable in the outer all the way in.
Replacing internal gear cables on bike together with outer casing that’s fitted internally.
If the outer casing is damaged and you need to replace it as well don’t remove the old cable yet.
- Take the new outer casing and measure it against the old one. Where it enters the frame, follow the tube until the outer casing reapers.
- Once measured cut it to the right length.
- When you cut the casing, the thin piece of P.T.F.E. tubing can close up so use a very thin piece of metal, like a pin or 1.5mm allen key to prise it open.
- If there’s an internal routing hole cover remove it from the frame.
- Remove the ferrule from the end of the old casing.
- Slide the new casing over the cut end of the inner cable until it meets the old outer. Join the two ends together with one layer of tape.
- Hold the old casing with one hand and the new one with the other and simultaneously pull the old outer and push the new one until the taped joint comes out.
- While holding the new casing with one hand remove the tape and slide the gear cable out of it.
- Attach a sticky tape so the casing doesn’t slide out. If this happens your task will take much longer than you anticipated.
- Remove the internal routing hole cover from the old casing. While holding the new casing with one hand remove the tape and fit the internal routing hole cover.
- Replace the ferrules to match the old casing.
- Push the outer all the way to the shifter and feed the new gear cable through.
- If required refit the cable provider under the bottom bracket.
Replacing internal gear cables on bike when cable is routed without a casing.
A Good way to replace an internal gear cable is to use PTFE tubing from the gear outer casing.
- First you need to measure the tube where the cable is routed and add about 30 cm.
- Cut the measured length of the gear casing.
- When you cut the casing, the thin piece of P.T.F.E. tubing can close up so prise it open.
- Use a utility knife to pare of one side of plastic coating.
- Now peel the coating and remove the wire strands. You now have your new internal routing tool!
- Shift the gear lever to the highest gear at the back or the lowest gear at the front.
- Find the end of the cable where it is attached to the derailleur. Undo the retaining bolt just enough to remove the cable.
- Where it is fitted the cable will probably be flattened and maybe frayed. Cut off the damaged end so that it will be easier to remove.
- For the rear gear cable take off the first bit of casing.
- If required remove the cable from the bottom bracket cable provider.
- Slide the PTFE tubing over the cut cable all the way until it stops.
- Hold the outer with one hand and the PTFE tubing with the other and simultaneously pull the casing and push the tubing until about 15 cm of tubing is showing.
- Tape that end of the tubing to the frame to stop it sliding out and remove the inner wire.
- Hold the top end of the PTFE tubing and remove the tape.
- Feed the gear cable through it until it comes out at the other end.
- Remove the PTFE tubing. Grab the bottom of the cable and pull it until the outer casing slots in to the cable stop.
Now it’s time to adjust the gears. If you need a help you can check out our article about gear indexing here.
You can also watch our video tutorial here:
You can also find out how to replace internal gear cables in our video tutorial here: