The Chainlink

Chainlink Tech Corner: How to Sheath Brake and Shifting Cables like a Pro

by Scott Wilson

A few years ago there was a thing called Gore Ride-On sealed cables and housing. By using multiple layers of sheathing they created a shifting system that was nearly immune to contamination. The cable was coated in Teflon, the housing was composed of layers of synthetics, and there was a plastic tube that connected all the housing stops so the cable could go from the shifter to the derailleur or brake without ever being subjected to the elements, except for a few centimeters by the fixing bolt of the derailleur. Cyclocrossers loved it because they didn’t have to replace cables after every race, but for normal people the Teflon-coated cable wore out and frayed too quickly. Gore ended production, only to have the sealed cable idea re-appropriated and refined by Shimano and their eleven-speed Dyna-sys cables.

Even if Gore didn't sell well, it's still a good idea to cover up exposed cables and housing ports. So in today's article I'm going to show you how to make your own sealed cable system.

What you'll need:

  • Brass ferrules. I prefer the kind made by Wheels Mfg.
  • Several feet of plastic tubing. You want an inner diameter a little greater than
  • 1.2mm for derailleurs and 1.6mm for brake, but an outer diameter (O.D.) around 2mm
  • Cable cutters
  • Measuring calipers
  • Tape measurer or meter stick
  • Power drill and bit to match the O.D. of the plastic tubing
  • Cable lube
  • Bench vise
  • Lots of clean rags
  • Felt tip pen

First, measure the outer diameter of the plastic tubing you'll be using as a sheath. Pick a drill bit that's as close to the same size as possible. Then, take your brass ferrule and set it firmly in the bench vise, open side down. Use a rag to keep it from getting scratched and be careful not to put it in so firmly that it gets crushed or deformed. There are other, more dependable ways of securing the ferrule in the vice, like a modified axle vise insert, but rags will do the job most of the time.

Here's the tricky part: while trying to stay perfectly perpendicular to the face of the ferrule, use the drill to enlarge the stock hole to the size of the plastic tubing's O.D., but try not to drill all the way to the other side. It might take a few tries, but only drill half way through each ferrule you intend to use. This is why I like to use Wheels Mfg. brass ferrules; they're a little thicker at the ends. The reason you don't drill through is because when the tubing sheath wears out it could have more opportunities to migrate into the housing and ferrule where it’d cause extra drag.

If you do drill through your last ferrule, life isn't over; there's another way to do the job. In the alternative version, you pull the sheath all the way through the ferrule and use a lighter to warm up a sharpened wheel spoke. Stick the hot spoke into the sheath and use it to expand the end so that it flairs like the bell of a trumpet. That'll hold the sheath in place and make a great seal against the elements. I've only tried this method with brakes because they can more easily overcome the drag from a degrading sheath end. If you try the trumpet method with your derailleur cables and it works well, please say so in the comments.

Now, measure the exact depth of the enlargement on each ferrule by sticking the drill bit or a piece of plastic sheathing into the enlargement and marking it with a pen where it exits. Pull it out and measure from the end to the marked point, which should be about 1mm or less. Write this down, it'll come in handy in the next step.

With the housing and ferrules in the frame, measure the distance of exposed cable between the two ferrule faces. Remember to add the depth of the enlargement from the previous step. This final measurement is how much plastic tubing you'll need to cut. Measure to the millimeter! If the tubing is too long it will bend the cable and cause mushy brake feel or bad shifting. If it's too short it will be useless. You might have to repeat this step several times to do it right.

With all the pieces cut and sized, you can thread the cable through the housing, ferrules, sheath, and on to the other side as normal. I like to liberally spread cable grease all over the cable and reapply it when it goes in or out of the ferrules, or into the plastic tubing. The grease helps to create a seal between the ferrule and the tubing, so use plenty. It will also help keep moisture out of the system.

Finish adjusting the cables to the brake or derailleur as normal. There will be a little bit of exposed cable between the final ferrule and the pinch-bolt, but that's unavoidable. You can buy little pieces of rubber accordion hose to cover that last part up.

And there you go: a nice sealed system that will prolong your bike cable's lifespan and improve performance.

I'd like to say a thank you to the master mechanic, George Majarucon, who taught me everything I've written about today, among many other facets of cycling and life.

Scott Wilson is an MFA writing student at Columbia College as well as a seasoned professional bike mechanic. Scott’s “wrenching” experience includes bike shops, racing teams, and professional triathletes across the US. The aim of Scott’s technical articles is to explain in detail how bicycles and their individual components work...and in doing so, help you keep your own bikes running better and lasting longer.

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