Depending on the type of cable, rust can do it in, too. And because the housing is often exposed to the elements, it’s at greater risk and can become corroded, cracked or bent.
The good news is that today most road bike cables and housings are high-quality. If you keep your bicycle maintained and don’t crash, they should last several seasons, at least. Once they bind or fail, though, they should be replaced.
In this and next week’s Tech Talk, I explain how. This week we go over the tools and materials needed, and how to check for bad cables and housing, in addition to removal. Next week, we’ll cover replacement.
Tip: One of the best reasons to pay attention to the condition of your shift cables and replace failing ones soon is because they can break inside the shift lever, right at the cable head. The head is made of soft metal and pulled tight into its holder with each shift. Since the holder is usually deep inside the shift lever and difficult to access, the cable head can be difficult to remove. You can avoid this hassle by keeping your cables in good condition.
Disclaimers: If your shift cable housing is wrapped beneath your handlebar tape, you may need to know how to remove and replace the tape to replace a worn-out cable housing section. Also, these instructions are written for road bikes with externally routed shift cables. If yours travel through the frame, they should last longer than externally routed ones. I don’t explain internal routing here, though it’s mostly just fishing the cable through.
Tools and Materials
You may not need all of these things, depending on your setup:
- correct type/size wrench for derailleur cable anchor bolt (usually 5mm)
- bicycle cable/housing cutter, such as Park Tool’s Professional Cable and Housing Cutter
- pick or awl (for re-opening housing ends crimped from cutting)
- replacement shift cable
- replacement housing
- cable caps/ends (crimp-ons for preventing fraying)
- housing ends (“ferrules” — if not already on your housing sections)
- electrical tape for finishing the handlebar tape if you need to remove and re-wrap it
- cable donuts/O-rings (if your cables hit your frame and rattle when riding)
Tips: Shift cables can be crushed and fray when you cut them, and housing can be difficult to cut. Special bicycle cable cutters sever cables and housing in diamond-shaped jaws for a clean, no-fray cut every time. If you don’t want to purchase cable cutters, which can be expensive (but a good pair should last a lifetime), you can get clean cuts with high-quality diagonal cutters, but test yours first on a scrap piece of cable and housing to make sure they’re sharp enough. A Dremel tool with a cutting disc will work, too, if you have one.
Checking and removing the bad shift cable
Checking the cable
Sudden hesitation in shifting or suddenly having to repeatedly use your rear derailleur adjustment barrel to tighten the cable (see last week’s Tech Talk) are common signs that the cable or housing are failing.
Check the housing first. It can crack or split or get bent or crushed, especially at the ends where it meets the stops on the frame. Inspect it from the handlebars all along its path to the rear derailleur for defects. There shouldn’t be any cracks, splits or wires protruding, and the runs should be smooth with no abrupt bends.
It’s harder to check cables because they can be mostly hidden inside the housings. So, instead of visually checking them, try to feel for issues. You can do this by first shifting into the largest rear cog. Then, get off the bike and stand next to it.
Now that the chain is on the largest cog, and you’re not pedaling, you can operate the shift lever without the derailleur moving. This lets you feel the cable. To do it, shift the lever back and forth while holding and pulling on the shift cable wherever you can hang on (next to the down tube on most bikes). A failing cable will feel rough or will bind.
Record how the cable and housing are routed
Before taking anything apart, look carefully at the cable and housing sections and make sure you know how it all goes back together again. Take photos or sketch it. In order of priority, the most important things to note are:
- Exactly how the cable is held at the anchor bolt on the rear derailleur (a bright light and magnifying glass can help here). Be sure to note which side of the bolt the cable is on.
- How external housing sections are routed from the lever to the frame.
- Whether there are metal or plastic ends on the housing and where they fit (again, these are called “ferrules”).
- How the bare cable is routed along and/or under the frame.
Tip: If you get confused or forget to take a photo, you can usually refer to how the front shifter’s handlebar housing section is routed.
Removing the cable and housing
If there’s a crimped end cap on the end of the cable near the cable anchor bolt on the derailleur, snip it off with a bicycle cable cutter. Then loosen the anchor bolt. Be careful not to loosen it so much it falls off the derailleur, rolls across the floor and vanishes!
You can now pull on the cable and it will come out of the housing sections and you can free them from the frame. Again, pay attention so you know how everything goes back together.
To get the cable out of the lever, make sure it’s shifted all the way back to its starting point. To do this, pull on the cable and shift the lever into highest gear. Now you can squeeze the lever as if you’re braking, look inside and you should see the silver round end of the cable (the cable “head”) inside the lever. If not, there may be a small plastic cap secured with a screw(s) on the lever that you need to remove first.
Once you can see the cable end, push on the cable and the head will come out of its holder so that you can pull it out of the lever.
Next week in Part 2, we’ll install the new cable and housing and get back on the road.
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s streak of consecutive cycling days has reached more than 8,000. Click to read Jim’s full bio.