Most places say to replace cables about twice a year, and housing once a year. That might be necessary if you ride in the mud every day, but for most people, replacing cables once per year and housing every year or two is enough. (I’ve gone 3-4 years between cable replacements without trouble.)
The key is to watch your cables for signs of wear, such as fraying, and replace them if they look worn. If your cables look and act like new, then there is no need to replace them. However, if they are wearing out, let’s replace them…
1. Get new cables.
The first thing to do is get a new set of brake cables and housing. Make sure to get brake cables, which are thicker than derailleur cables, and brake housing, which is made from a single flattened and coiled piece of wire.
2. Check your current set-up.
Before you touch your bike, take a look at how the cables are currently routed. For example, how they wrap around the frame and handlebars and where they attach to the brakes. You’ll want the new cables to be routed the same way.
3. Remove cables.
Take a hex wrench (usually 4 or 5 mm) and loosen the pinch bolts on the brakes, then slide the cables out. (Cut the cable end caps off if necessary.) Then you can remove all the cables and housing and slide the ends out of the brake levers.
4. Prep new cables.
Now it’s time to cut the new cables and housing. The best way to do that is to line up the old and new cables side-by-side, and cut all the new stuff to match. Make sure to cut the cables and housing using bicycle-specific cable cutters, and then file the cable housing so it’s smooth. Then you can crimp ferrules (end caps) onto the cable housing.
5. Barrel adjusters.
Before installing the cables and housing, reset your barrel adjusters. On both the brake levers and brake calipers, turn the barrel adjusters all the way in, then back them out two to three turns. This will allow you to fine-tune the adjustments later.
6. Install housing.
Install the cable housing by placing it in the frame’s cable stops.
7. Install cables.
Starting at the brake levers, install the cable, making sure it is seated in the lever properly. Then slide the rest through the housing and under the pinch bolt on the brake caliper. Pull the cable taut to where the brake pads allow a little clearance around the rim, and tighten the pinch bolt. Then crimp on the cable end caps to prevent the cables from fraying.
8. Final adjustments.
Pull the brake levers and check the feel. Now you may want to pull the cables tighter if there is a lot of slack, or just make some adjustments to the barrel adjusters to get the best feel. (Dialing out the barrel adjusters will take up slack, while dialing them back in will create more slack in the cable.)