How To Replace Your Bike Brake Cable
Like on any vehicle, brakes are one of the most important systems of a bike. Bike brakes are controlled by a bike brake cable which needs to be replaced periodically. The operation is not that complex and, if you love DIY, you could even try to replace your bike brake cable by following this step-by-step guide.
Understanding Bike Brake Cables And Their Outer Casing
Usually, bike brake cables have a diameter of about 1.6 mm and are controlled by a lever which, when pressed, causes the brake pads to stop either the rim of the wheel or the disc. For a good grip, the bike brake cable should undergo a tension which should be divided into a rough draft during the mounting phase and a fine adjustment through the tension screw found on the body of the brake.
The brake systems are different depending on the type of bike and they might also vary depending on the type of brake installed on the bicycle. For this reason, it is always recommended to buy the right type of brake cable and outer casing that is compatible with your bike.
Regarding the outer casings, they usually have an outer diameter of 5 mm and an internal one of 1.6 mm. The metal filaments constituting the outer casing are typically disposed in a spiral along the entire length of the case.
This design triggers a more rapid response from the brakes and allows cyclists to exert a weaker tension on the brake lever. In fact, thanks to these filaments the outer casing of the brake cable is able to transmit power without requiring too much effort.
Moreover, the outer casings are usually internally coated with a Teflon layer that increases the sliding of the cable inside the case.
The caps of the outer casing can be made of steel or plastic, depending on the manufacturer’s choice.
Why Is It Important To Change The Bike Brake Cable?
How many times do you brake during a trip? Each time you press the braking lever you induce stress into the system, which imperceptibly but continuously degrades the cable and its outer casing. For this reason, the bike brake cable should be replaced every two years, if there is no obvious damage, or even more frequently if you’re using your bike for training.
Because it is made of spirally wired metal filaments, the cables can corrode, while the water and dirt can infiltrate into the outer casing and reduce the sliding of the cable. But when is a mandatory replacement required?
If the bike brake cable needs to be replaced, it is recommended to replace the whole system that includes the cable, outer casing, casing head and wicker.
How To Replace Your Bike Brake Cable
Replacing the brake cable and the outer casing is a simple operation that only requires minutes. To replace the brake cable you will need:
In this article, I will focus on replacing external bike brake cables. The cables with internal frame transition will be treated in a dedicated article.
Step 1: Cut the cap of the cable
With the wire cutter, cut the cap of the cable right above the point where it meets the cable, in order to untwist the spiral.
Step 2: Release the cable
With the correct key, loosen the retaining screw without removing it and release the old cable. The type of key is different from bike to bike, but usually, you will need either a 5 mm Allen key or a 10 mm English wrench.
Step 3: Remove the old cable
At this point, the brake lever must have become very weak to pull. Lower it and look inside, where you should see the end of the brake cable. Push the cable from one end until it comes out. If the cable is worn out, jammed or folded this operation might require a few minutes of patience.
Once you’re able to grab the cable with the hand, pull it out to remove it completely. In the case of special braking systems, such as U-brake or V-brake, you might have to dismantle a few components to do this operation.
Step 4: Remove the outer casing
The outer casing should also be replaced together with the brake cable. To remove the old one, pull the outer casing towards you and out of the body of the brake lever. You should now remove the outer casing from the fasteners fixed on the bike’s frame.
In some cases, the outer casing is fixed with latches that are welded to the frame. On the contrary, on some bikes, the outer casing might simply be fixed with clamps that need to be cut, so consider their eventual replacement too.
In the case of the racing bikes, the outer casing is usually fixed to the handlebar with insulating tape. In this case, remove the tape by cutting it with a cutter, paying attention not to pinch the outer casing if you want to reuse it.
Step 5: Measure the size of the outer casing
To determine the correct length of the new outer casing you can use the old one as a template and cut the new one to the same size. Nevertheless, it is always better to take a new measure directly on the frame.
To do this, insert an outer casing cap in one end of the outer casing and mount it on the braking system on the lever. Make it run along the frame of the bike until it reaches the body of the brake. Make sure that the position of the cable allows you to turn the handlebar effortlessly but make sure that the curvature is not too accentuated, to prevent the sliding of the cable.
While measuring the length is uncomplicated for the front brake, things are less straightforward in the case of the rear brake. In this case, you’ll have to pass the cable through your seat at the right angle, otherwise, you risk to limit the smoothness of the cable.
Step 6: Cut the outer casing
Once you determined the right length of the outer casing, cut it with the wire cutter. The cut must be decided and clean, without grubbing.
Once the cable is cut, use the screwdriver to open the hole. This operation is important because cutting always tends to crush the Teflon coating and prevent the cable from sliding. Once the hole is widened, fix a plastic outer casing cap on the end.
Step 7: Insert the cable inside the lever
Lower the brake lever to locate the brake cable entry point. Then, slide the cable from the terminal-free part. In the case of V-Brake brake levers, the cable must slide out from the adjusting screw, while in the cruiser bicycles the cable comes out from the back of the body. Pull the cable and match the terminals with the brackets inside the lever.
Step 8: Install the outer casing
Insert the cable into the first sheathing piece and fasten it to the handle and to the clamp. The inside of the outer casing is not greased, as the Teflon coating allows for a high degree of smoothness. Fix the first piece of the outer casing and turn the handlebar in both directions to check if it feels strange.
If moving the handlebar in any direction feels odd, try shortening the outer casing. On the other hand, if the handlebar doesn’t rotate completely but remains locked by the casing, it means that it is too short and you’ll have to replace it with a longer piece.
In the case of racing bikes, the outer casing must be secured to the handlebar with insulating tape. To do this, simply wrap the tape around the handlebar and outer casing.
Once the outer case is installed, cover the ends with plastic caps and engage them in the clamps, then run the cable along the frame of the bike until it reaches the body of the brake.
In the case of cruiser bikes, the outer casing is housed inside the tensioning screw, while in the case of the V-Brake, the outer casing is clamped into a steel element.
Step 9: Fix the cable to the retaining screw
Grab the cable with your hand or with a solid third-hand tool, tighten it slightly and allow it to pass through the groove present on the plate of the retaining screw.
In the case of V-Brakes, the cable passes directly into the screw which has a hole in the cylindrical part that is used to lock the cable against the arm of the brake.
Holding the cable in position, tighten the retaining screw. Check that the screw is tightened to 5 Nm with a torque wrench, as in this way you’ll be able to make further fine adjustments.
Step 10: Cut the excess cable
Measure a length of 2 inches from the retaining screw and cut off the excess cable using a wire cutter. Make sure the cut is clean and precise.
Once the cable and the new outer casing are mounted, you can adjust the tension of the cable and make the lever more responsive, depending on your personal preferences.
Before hitting the road, remember to try the brakes on a street with moderate traffic so you can record and fix any defects. Don’t forget that even if the brakes seem to work well, they might give you unpleasant surprises when in the saddle, so make all adjustments before taking any risks.