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I just discovered an issue with a shifter cable housing and want to share some details in case anyone sees the same early warning signs. I also have some questions about the issue.

The front derailleur shift cable housing on my bike, for at least a couple of years, has been a bit wavy looking. You can see it on the left here: enter image description here

Up until recently there was no degradation in shifting so I assumed it was just a weird UV effect degrading the plastic housing and making it ripple.

However, about a month ago I noticed my front derailleur needed some tension added. I did that with the barrel adjuster. Then the next ride, it needed a bit more tension added. This continued, needing more tension almost every ride, until I ran out of barrel adjuster thread.

Yesterday I inspected the whole system a little closer, expecting to find the cable was slipping at the derailleur attachment point or something. However, it turns out the wires that are embedded in the housing have popped out the ends of the housing, on both ends:

enter image description here

enter image description here

This explains the continual adjustments I was needing to do. The cable wasn't slipping or stretching, the housing was compressing. It also explains the ripply housing.

Anyway, I wanted to share in case anyone notices some ripply or wavy cable housing. Again, this housing's looked like that for two seasons now, so if I'd known what that meant, it would have been a very early warning sign.

My questions are:

  1. Is this a normal failure mode for cable housing?
  2. This housing is about 6 years/ 8,000km old. Is that a reasonable amount of time for a housing to last? The factory housing lasted about 6 years/ 12,000km.
  3. Is there anything else I should check in my setup that may have contributed to this failure, to make it less likely to happen again?
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  • This can also be described as a "corkscrew" effect on the casing. I've seen one where it looked like wire drawn sideways off a roll, the corkscrew was so bad.
    – Criggie
    Aug 21, 2022 at 19:25

2 Answers 2

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  1. Normal-ish, yes. It's normal enough that when one sees that kind of kink or distortion on a housing, it's assumable that the wires are likely to be pulling through somewhere.
  2. Yes, reasonable and then some. Note though that the ferrule's lifespan is what's in question here, not the housing. Some mechanics favor aluminum or brass ferrules because they tend to completely eliminate this kind of failure. They have other downsides - they are expensive and can cause creaks as the bars turn, and generally speaking housing will begin to degrade in performance long before the ferrules blow through. Still though, the argument exists that plastic ones shouldn't even exist since they basically create a failure mode that doesn't exist otherwise. (I've known owners of repair-oriented shops that simply don't use plastic ferrules because of the belief they are a net negative on a functionality/reliability level, and that philosophy does work. I would rather have aluminum or brass if I was going to be in the middle of nowhere with the bike, for example. The problem for a shop is that you're trading the risk of a customer coming back with a blown ferrule for that of coming back with a creak, and you're going to either have to charge more for something that will be relevant to hardly any customers or have a niggling and probably unnecessary conversation about the topic with each one, and both of those things are actually pretty bad.)
  3. If you have any kind of circumstance going on that creates the need for high input force on the shifter from your hand, that will make this problem worse. Most of the time I've seen this, there's some kind of setup issue or other source of excess housing friction.
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  • 1
    The creaking problem should be fixable with a tiny dab of grease, though. Nothing worth abandoning a rock-solid solution for. Aug 21, 2022 at 17:42
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    @cmaster-reinstatemonica So goes the argument for them. The counterpoint is you don't necessarily want to have to grease them all preemptively, but if you don't then you'll probably get some bikes back that need the grease application, and that is a failure itself. Aug 21, 2022 at 17:50
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    For someone working on their own bikes, there's no real downside. Aug 21, 2022 at 18:03
  • Indeed. Especially if the one working on their own bike does not mind a bit of creaking in the first place. Nevertheless, it's routine to grease (some) screws when they are installed, so I guess, it could also be routine to do the same on the ferrules. I understand that market forces are pulling towards cheap and easy to install rather than durability, and I understand that's precisely why they are alien to me ;-) Aug 21, 2022 at 20:27
  • I find the plastic ones sometimes do a better job of strain relieving the housing. I installed one where the housing enters my RD and there’s now a split in the plastic sheath right at the open end of the ferrule.
    – MaplePanda
    Aug 21, 2022 at 22:29
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Its best to just replace the housing and cable when it gets to this point regardless of the lifespan you would expect. The reason for part of the cause of the housing wires poking through is that the housing has been flexed severely/and or frequently enough to cause the wires to migrate out and through the ferrule. If your cable needs to do a lot of flexing, using higher quality ferrules can reduce this kind of degradation. But eliminating the housing failing like this is your primary goal, and just using metal ferrules doesn't necessarily solve the issue. eliminating over flex is a good practice. if the housing is regularly flexing in a severe way, using a slightly longer length of cable housing might alleviate how much it must flex.

Also, in the first pic it looks like the housing has been really mangled and maybe slightly kinked. It's possible that the cable inside might have a harder time sliding freely if there is even a mild pinch, which can effect the function of your derailleurs, as they are spring loaded and if the housing is pinching the cable enough to overcome the spring force of the derailleur, sometimes you'll notice some lag or in shifting or drifting out of gears.

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  • Concur - this is an excellent time to detail strip and clean the derailleur too. Subtle damage like bends can increase resistance to movement but still function. Less resistance in all parts is ideal.
    – Criggie
    Aug 22, 2022 at 1:21
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    @Criggie I actually started the "bad shifting" investigation by taking the derailleur off and degreasing it. I haven't done that in years, so I thought maybe an accumulation of road grime + grease was causing the whole thing stiffen up. It wasn't until after doing that that I worked back along the cable route and found the failed housing discussed above.
    – SSilk
    Aug 22, 2022 at 20:08

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