In this article I’m going to explain how to replace a cantilever brake cable. In this case it concerns my Scott Town XC, which has a low-end Shimano 200GS setup.
Both the cable housing and the inner cable itself has probably never been repaired. This means the cable is roughly 30 years old. And even if I’m wrong in my age assessment, it was clear the cable was in need of replacement.
Replace a cantilever brake cable video tutorial
Why and when to replace a cantilever brake cable
Re-adjusting the brakes had caused some of the individual strains to break. With a new cable this isn’t possible, but with a rusted one it is. I’ve ridden hundreds of miles with the cable in this state, but common sense dictates it’s safer not to.
There was also a significant amount of rust on the cable. When I pulled the cable through its housing you could clearly see some of it coming off and accumulating on the top tube. After I had replaced the cantilever brake cable the difference with a new cable inside a lubed housing was significant.
What brake cable do you need?
You need to check what type of cable you need. With one of the most important elements of the brake cable being the cable head. This kind of knob fits in the inside of your brake lever.
Although you probably need a cable with exactly the same cable head, which is most common, there are varieties.
You can check the cable head by looking at the underside of your brake lever. You should be able to see the cable head in the brake lever case.
Step 1. Removing the cantilever brake cable
Since I replaced a cantilever brake cable I’ll need two different size spanner wrenches and a pincer to cut the cable.
Since you won’t be reusing a worn out rusted cable you simply cut it. You’ll need to or else the frayed end will get stuck in the cable housing.
The cable is also kept in place with screws. One for a single cantilever brake, and one for the straddle cable yoke.
Quite some force was necessary to pull the cable through its narrow housing. It’s not necessary to remove the outer cables. You can simply leave them in place, unless of course you also plan to replace these.
Removing the brake cable entirely is easiest if it only hangs in the brake lever by the cable head. This way you can easily manipulate the cable head out of its case. By pulling the brake lever you create an opening to reach the cable between the lever and the adjusting nut and barrel.
Step 2. Putting the new cantilever brake cable in place
Before I install the new brake cable I put some sewing machine oil in the cable housing. Both gravity and the insertion of the new cable will make sure the oil will be spread out across the entire inside of the housing.
Inserting the new cable starts by placing the cable head inside its cage.
The end of the new cable is welded together, which ensures it won’t fray and makes pulling it through the cable housing a piece of cake.
Step 3. Checking your brake shoes
Now is also a good time to check the brake shoes if they are worn out and in need of replacement as well. Usually installing a brake cable necessitates brake adjusting anyway so you can save yourself the hassle of doing it twice if you replace the brake shoes at this time as well.
In my case I decided the brake shoes had some more usage in them, evident by the margin of rubber above the wear line.
Step 4. Overhauling the adjusting nut and barrel
The adjusting nut and barrel are parts of the brake lever that enable you to finetune brake cable tension. They consist, logically, of a nut inside a barrel. The cable housing sits inside the barrel.
By rotating the barrel counterclockwise the nut is moved outward, effectively lengthening the cable housing and putting more tension on the cable inside it. Obviously rotating the barrel clockwise releases tension.
My brake lever nut and barrel were moved to its limit, disabling its ability to add more tension to the cable. Some slight corrosion also made it extremely difficult to actually rotate the barrel.
So first off I put some sewing machine oil on the nut and rotated it a couple of times to make it move more freely.
When you replace a cantilever brake cable I move the nut all the way into the barrel (clockwise). When it can move no further I give it a single rotation counterclockwise.
Usually you’ll need to add a bit more tension initially and some cables may stretch overtime (unusual nowadays with high-quality brake cables). This way you have the option to both add tension and release tension.
Step 5. Cable tensioning and brake adjusting
The last step is to actually tension the cable after you’ve pulled it through the yoke and brake arm itself.
Initially I tighten the cable in such a way that both brake shoes are against the rim and then add 1 to 2 mm.
I can fine tune the brakes later by readjusting the brake shoes or the tension screw inside the brake arm (these brakes only have one per pair).
If you’re happy with your brake adjustment it’s time to cut the cable about 5 cm. or 2 inches from the brake arm. A professional brake cable cutter keeps the cable from fraying when pressure is applied, but that specialty tool is very expensive. I didn’t do it this time, but maybe putting a piece of tape around the cable will help in preventing this from happening.
I always seem to have no cable crimp sleeves so again I was forced to reuse the old one. You can widen the squashed part of the sleeve by inserting a nail into the opening. But the whole concept of bike restoration is about reuse, so reusing even the tiniest bit like a crimp sleeve feels kind of poetic.
I make sure the crimp sleeve stays in place by using the exact same pincer but applying less pressure (I have snipped sleeves in the past).
Some final adjustment with the help of the brake lever barrel and the job of how to replace a cantilever brake cable is done.
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