If you have a rusty cable, or one that snapped then your gears will shift poorly or even stop working and the cable will need to be changed. If replacing gear cable on bike feels like a tricky task to you then do not fear. In this article we will guide you through this process step by step so you can successfully replace the gear cable on your bike.
Most derailleurs are operated by a cable that’s tightened or loosened when applying the shift lever.
- If the cable or its outer casing are faulty your gears might not work properly.
- Too loose cable will cause the derailleur not being able to reach the biggest sprocket or chainring.
- If the cable is rusted it will not move smoothly through the outer casing causing poor shifting.
Types of gear cables
Gear cables are mainly made of two materials:
With one or two exceptions, all brands and styles of gear lever use the same cable ends.
When replacing a gear cable on a bike it is a good practice to also change an outer casing.
The outer casing consists of many thin lengths of wire held in place with a plastic coating on the outside and a thin P.T.F.E. tube running the whole length of the casing on the inside. This striated wire system is crucial for precise indexing.
Replacing gear cable on bike – tools required.
- 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.
Removing the gear cable from the handlebars
- To ensure the cable slots in the correct position, shift the gear lever to the highest gear at the back and 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.
If you unscrew it too much, the washer might change position without you noticing. It is important for accurate shifting that you position the washer correctly.
- 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 drop bar levers, turn over the bracket cover from the back side and, if necessary, remove the handlebar tape up to the gear lever and any sticky tape or insulating tape holding the outer casing in place.
Removing the cable from the frame
- Pull off any outer casing and set aside. If there’s more than one piece, remember which length goes where.
- If you have full casing running from the lever to the derailleurs, make sure that you remove any attachments, such as cable ties or plastic retainers.
- If you have an internal routing and are not sure how to remove and fit the cable watch this video to follow step by step guidance.
- Some drop bar lever bikes have inline cable adjusters fitted between two pieces of outer casing near the lever.
Inline cable adjusters work in the same way as regular barrel adjusters. They consist of an outer barrel, slightly narrower inner barrel and sometimes a spring.
Turning the outer barrel anticlockwise will add tension to the cable.
Turning the outer barrel clockwise will reduce the gear cable tension. 
- Put the inline cable adjusters aside as you will have to refit them later.
- Screw any gear barrel adjusters all the way in.
Finding which way the cable attaches to the lever
The cable attaches in different ways depending on the model of lever. If you’re unsure about where the cable enters and leaves the lever then check the technical documents. To do so find the code or serial number on the shifter. For drop bar levers it’s usually under the hood and for flat bar levers it’s usually under the shifter body. Use this code to find the Dealer or User manual documents. We’ve added some useful links below.
Removing the gear cable from drop bar levers.
In our example we are using Shimano 10 speed Tiagra.
- Remove the cable cover from the bracket.
- Gently push the gear wire from the trimmed end so that the cable end emerges from the lever. If it’s sticking, jiggle it a bit until it moves.
- When it is a little way out, hold the end and pull the wire out of the system.
Removing the gear cable from flat bar levers.
- Carefully remove the bolts. Remove the cover from the casing or the inner hole cap on the side.
- Gently push the gear wire from the trimmed end so that the cable end emerges from the lever.
- When it is a little way out, hold the end and pull the wire out of the system. If it’s sticking, jiggle it a bit until it moves.
- For STI levers, prise out the nipple with a pick or slim, flat bladed screwdriver.
Preparation.
When replacing a cable it is good practice to change the outer casing and ferrules as well.
- You need to cut the outer casing so it the right length. Use the old outer casing as a guide.
If you have fitted a longer stem or wider handlebars the new outer casing might need to be longer to allow full handlebar movement.
- When you cut the cable, 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.
- When you have cut and opened both ends, run the inner wire through it to make sure that it runs smoothly.
- Now fit the new ferrules to match the old ones. They are designed to stop the outer casing coming apart. Press the cable end against a hard surface. Make sure that they are fully engaged.
Replacing gear cable on bike with drop bar levers
- Slide the inner cable through the entry port.
- Now push it further into the lever. You might need to manipulate it a bit as it has to fit in a designated slot.
- Push the cable all the way in so that the nipple sits in the designated slot in the unit.
- Feed the inner cable through the outer and push the outer into the lever. Some Shimano levers use a special short tongue ferrule. Insert the convex shape on the ferrule into the groove in the unit.
- Reinstall the cable cover.
- For non exposed cables, place the gear outer casing along the brake outer casing on the bar and tape it so that it stays in position.
- Now replace the handlebar tape. Our article here will guide through this task.
You can also watch our video tutorial:
- Fit an inline cable adjuster if necessary. It is a good practice to feed the gear cable through starting with the inner barrel.
Replacing gear cable on bike with flat bar levers
- Install the inner cable so that the nipple sits snugly in the lever. You might need to manipulate it a bit as it has to fit in a designated slot.
- Refit the cover or inner hole cap.
- Feed the inner cable through the outer and push the outer into the lever. Route the outer casing but make sure that you don’t tangle the cables.
- Start fitting the outer casings in the required stops, or feed the cable through the frame. If you have a full external casing attach the cable guides.
- If the cable runs along or inside the down tube then under the bottom bracket shell there will be a cable provider. This usually has two slots. The one for the front gear cable is situated centrally and the one for the rear gear cable is placed closer to the crankset.
- Feed the cable through the hole in the provider.
Now it’s time to position the cable into the derailleur.
- Feed the inner wire through the cable stop or barrel adjuster.
- When you are fitting the cable under the pinch bolt it is very important that you position it in the way advised by the manufacturers. There will be a groove, either on the derailleur body or on the washer.
- Feed the cable along the groove and tighten it.
- If you fit it incorrectly the derailleur might not shift properly.
- If there is a lip on the washer don’t move it to cover the cable. It is designed to stop the washer from spinning.
When the cable is in position it is time to adjust the gears. Our article here will guide you through this task. You ca also watch our video tutorial: