jeffreythree

New one on me, but I just work on my own bikes. Any idea how this happened? It is the original Jagwire Lex cable housing for the rear derailleur on my Jamis Renegade. Both ends look like this with half the wires of the housing shifted various distances out of the outer housing, and the outer housing torn up under the ferrules. I have seen frayed, but not that shifting of the wires. The bike is only 2 years old and has less than 2000 miles, mostly this summer. Cables are a bit to long after lowering the bars; so I just recut the housing for now and used a new cable. I wonder if I should replace all of this housing on the bike?

Andrew R Stewart 

This happened because you used your bike, and likely didn't replace cables as frequently as you obviously should have. We see this casing strands migrating lengthwise often enough. On cheap as well as quality bikes. But, regardless of my somewhat tongue in cheek opening, I have never yet had anyone explain why it happens to the green bike but not the blue one given both having a similar situation. We have concluded that the short term fix is simple, replace the casing loops (and inner cable as precaution). The long term avoidance is monitoring and servicing more frequently.

My personal thoughts are that when the casing gets flexed frequently the casing strands can loose their ability to keep as a unit (all the strands act in unison) and some will migrate. My evidence for this theory is that we almost never see this with the casing loops that are between non moving stops but do see it when there's a stop on the frame and the casing's other end is (usually) at the shifters. So the steering rotations of the bars are the flexing I refer to. Andy

alcjphil

Just wondering if you used proper ferrules for shift housing. If the ferrules were designed for brake housing the casing ends will not be properly supported and they can push through the larger hole in the brake cable ferrule

Andrew R Stewart 

We see this problem with both the proper steel SIS ferules as well as the plastic ones. Andy

pdlamb

Would painting the bike blue work?

Troul 

It comes from being used. Only way to stop that is to not use it... or possibly painting the bicycle cyan?

HillRider

Yes, but alcjphil's point was if the OP's bike came with brake (5mm) ferrules rather than shift (4 mm) ferrules, that could explain the housing fraying.

Andrew R Stewart 

Sure if a bike was equipped with the wrong ferules it would increase the likely hood of problems. This isn't a common thing but it does happen, more often after a casing replacement had been done by someone who wasn't informed of the improper ferule issue (or didn't care, thankfully these people are few, IMO).

To add detail though- SIS casing has been made in both 5mm and 4mm diameters. Brake casing is nearly only 5mm. So to use a steel brake casing ferule on a 4mm SIS casing means that the wrench (be they pro or home) wasn't able, or didn't, notice the fit being wrong. Not saying this doesn't happen, just that it requires two mistakes.

I'll also note that casing strand punch through (as when a brake casing ferule is used on a SIS casing, regardless of diameter fit) is, IME, generally not the same as what the OP is showing. Andy

dsbrantjr

Did you form the cable housing to its approximate final shape before you cut it? If you left it straight while cutting it, when you bend it to its working shape you will stress the strands in just the pattern that is exhibited. This is most apparent in the loop of cable going to the derailleur since it makes a sharp almost 180 degree bend.

JohnDThompson 

Or upgrade to friction shifting and coiled housing.

jeffreythree

Makes sense, I thought housing would last longer than 2k miles though. If I rode this bike all year, I would be changing housing out every 6 months. The Shimano housing on my other bikes last a lot longer than that. I expect to change cables more frequently than the housing, but this cable was fine.


It is already blue.

It was installed by the manufacturer and assembled by the local bike store. Ferrules are steel and fit properly.

Ha! Several of my bikes have friction shifters, and I have even considered switching this one out to Gevenalle Audax friction shifter/brake levers from the current Claris brifters.

masi61

This is a good point. I have a Shimano cable and housing cutter tool that has a ferrule crimper on it. The idea is that once the housing is cut to length, you put the (metal) ferrule on it then crimp it with this octagonal shaped pattern which then keeps the ferrule in place. Now these were Shimano Deore XT compressionless housings that were quite thick. I notice that road dereailleur compressionless housing is not a thick and it is usually terminated by nylon ferrules which are not crimped but are a snug fit.

I like the idea of bending the housing to the desired shape before cutting to allow the lengthwise strands to be allowed to orient themselves first and then once terminated the trimmed section might have waste wire strands of slightly different lengths.