Bicycle brakes are an integral part of a bike because they are what stops it from moving. If they don’t work properly, they will need to be fixed before you can safely use your bike again. A bike brake stops the bicycle from moving by jamming rubber (rim brakes) or metal and fibres (disc brakes) against the rotating wheels. Most of the bike brakes are operated by a cable that’s been pulled when pressing the lever, compressing the callipers onto the rim or pistons onto the disc rotor. There are a number of reasons why bike brakes don’t always work, such as, the calliper being broken, pads being worn or contaminated, levers being faulty or the cable having issues. In this blog we are going to concentrate on the last problem and show you the secrets behind bike brake cable replacement.
What can cause a need for bike brake cable replacement?
- The cable is rusted or corroded- Rust (orange coloured) and corrosion (white and powdery) inhibit the cable moving smoothly in the outer casing. If they are really rusted/corroded then you will be unable to make the brake work however hard you squeeze the lever. If the problem has only just started, then the spring in the brake won’t be powerful enough to return the calliper to its original position and the pads will just stay on and rub against the rim/rotor.
- The outer casing is bent- The outer casing has a steel coil running along the length. This can get bent and then inhibits the inner wire running smoothly. Even if you can operate the brake with the lever you probably won’t be getting maximum performance.
What is the brake cable made out of?
Brake cables are mainly made of two materials:
- Galvanised steel- Significantly less expensive to manufacture than stainless steel, however susceptible to rust causing the cable to seize in the outer casing and eventually to break.
- Stainless steel- Offers great resistance to corrosion. Thanks to its sleek surface it travels in outer casing much more smoothly.
Some stainless steel cables are also coated or polished to further reduce friction. These are the most expensive. Most cable manufacturers offer these specialist cables.
What’s on the end?
On one end… nothing. It just finishes. I’ve bought it up because I think it’s important to note that the end is sealed. If the sealing is done properly (and most are) the thin strands of wire that are wound together to form the cable can’t unravel. It means that the cable can easily be pushed through the outer casing and under the pinch bolt without one strand getting caught. Make sure that you don’t trim the cable to size until you have finished threading it through the outer casing and attached it to the brake otherwise you’ll lose this helpful addition.
What’s on the other end?
The non-soldered end has what we call a nipple or cable end. The two most common are:
- Pear nipple, thus called because it looks a bit like the fruit. It’s used on drop bar levers found on road and gravel bikes.
- Barrel nipple, so named because it is a bit barrel shaped. This is used with flat bar levers found on mountain bikes and hybrids.
There are, of course, exceptions. Vintage Campagnolo have a smaller diameter pear nipple and some old Brompton levers use pear nipples even though the lever is a flat bar design. These are just two examples. There will be plenty more!
As well as the thin cable that runs from the lever to the brake caliper, there is outer casing consisting of a tightly coiled steel tube, offering flexibility and strength. It is covered in a thin plastic sheath to stop the coil corroding and inside is a thin P.T.F.E. tube running through the whole length of the casing allowing the cable to have a smooth run. It has a 5mm diameter meaning that the 1.6mm diameter brake cable can run comfortably through it without snagging.
- 5 mm allen key or 8/10mm spanner. They are used for releasing and tightening the cable at the caliper.
- Cable cutters. They differ from pliers and snips as the blades cross over each other. They are the only guaranteed way to cut inner wires and outer casing without damaging it.
- 1.5mm allen key or a pin. Useful to prise the closed up P.T.F.E tubing. When you cut the outer casing, the thin piece of tubing inside can close over. Making sure that it is open means you get the smoothest run of inner wire possible.
Bike brake cable replacement– removing the cable.
- For drop bars first remove the handlebar tape up to the brake lever and any sticky tape or insulating tape holding the cable in place.
- If you have full casing on a rear brake, make sure that you remove any attachments, such as cable ties or plastic retainers.
- Find the end of the cable where it is attached to the brake caliper. Undo the retaining bolt.
- Where it is fitted will probably be flattened and maybe frayed, so cut off the wire so that it will be easier to remove.
- For “V” brakes, remove the rubber boot and noodle and set aside.
Pull off any outer casing and also set aside. If there’s more than one piece, remember which length goes where.
For caliper brakes and cable disc brakes reset the barrel adjuster on the caliper.
For flat bars turn the barrel adjuster and lockring on the brake lever so that the slots line up with the slot in the brake lever.
Pull the lever blade and slide the cable through the slot.
Swivel the cable so that you can release the end out of the lever.
For drop bars, pull the brake lever and keep it in the open position by attaching it to the bars with a cable tie or toe strap.
Gently push the brake wire from the trimmed end so that the cable hook unit stays in place. The pear head will emerge from the lever. When it is a little way out, hold the end and pull the wire out of the system.
Preparation of bike brake cable replacement
- When replacing a cable it is good practice to change the outer casing and ferrules as well. The ferrules are the plastic or metal covers that go over the end of the outer casing to stop it fraying or coming apart. They add a tiny bit to the diameter of the casing, so if you find that the outer casing won’t fit comfortably into wherever it’s going, such as the guide pipe, drop bar lever or caliper, then leave the ferrule off as the tight fit of the casing will stop it coming apart.
- The outer casing needs to be cut to 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 the cable is cut, because the inner is coiled, the metal end can curl over the hole and stop the cable from passing through smoothly. Use your cable cutters to snip off the offending end.
- Also, the thin piece of P.T.F.E. tubing can close up when cut 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 trimmed 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 unravelling.
- For V-brakes check the noodle or guide pipe for damage. If it’s bent the cable might not be able to pass through it smoothly. Replace it if necessary.
- Check if the ferrule is required.
There are three main types of noodles:
- 90 degree angle– This noodle is used for rear brakes and also front brakes where they are operated from the left hand side lever.
- 135 degrees angle– This noodle is used for front brakes where they are operated from the right hand lever.
- Flexible- This noodle bends enough so it can be used for both front and rear brakes. You will often find it on folding bikes where the flexibility stops it getting damaged when the bike is being folded and unfolded.
Bike brake cable replacement
- For flat bar levers take the cable and slot the barrel end into the lever.
- Slide the cable through the slots on the lever, lock ring and barrel adjuster.
- Turn the lockring towards the end of the barrel adjuster. Reset the barrel adjuster.
- Fit the required piece of outer casing.
- For drop bar levers take the cable and slot it into the cable hook unit.
- 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 pear end sits in the cable hook unit.
- Release the lever.
- Fit the required piece of outer casing.
- Now place it along the bar and tape it so that it stays in position.
- Replace the handlebar tape. Watch our video here if you’re not sure how to do this.
- Route the outer casing, making sure that it isn’t tangled with the other cables.
- Fit the outer casings in the required stops. Make sure when you route the outer casing that it isn’t tangled with the other cables.
- If you have full casing, attach it to the cable guides.
- For V-brakes fit the noodle and slot it in the bridge.
- Now refit the rubber boot.
- For cable disc brakes and road brake callipers slot the cable through the barrel adjuster and into the pinch bolt.
The next step is the brake adjustment. You can find out here how to do it on rim brakes. Click on this video to learn how to adjust disc brakes.
Don’t cut the cable yet, leave it until after the final adjustment. This is in case you have made a mistake somewhere along the line and you need to start again. Feeding a cut cable where the unsoldered end can unravel will make the job so much more difficult, if not impossible