Originally Posted by
drpaddle
Well, I'm not a Jagwire fan. The steel wires in the casing run parallel to the length, instead of coiling like classic housing. On a recent ride, that enabled my rear derailleur cable to actually slice through the side of the casing. That disabled the derailleur. I was able to lock it into one gear and finish the very hilly ride shifting just my three chainrings. Yes, I admit quite a bit of fault in the failure: I didn't use proper end caps on the casing, and I didn't lube the vintage derailleur adequately and it became tough to move. I also used the Jag casing in an area requiring a tight bend, and it doesn't like to bend like that. All in all, though, I installed it just as I would have installed classic casing. I replaced the damaged section with vintage spiral casing, and everything works great again. Bike is my 1970 Mondia Special 650b conversion.
...your photo of the damaged housing is "indexed" derailleur cable housing, If you're mostly doing friction shifting and brake cabling, you should be using Jagwire brake cable housing. It's a sprial wound steel coil housing, and can also be had with a plastic liner. It's much more flexible, and it won't asplode like that, even if you put it together without housing ends.
REally, the only reason you'd want to use housing like the stuff in your photo is for indexing derailleurs One possible exception is Campy NR rear derailleurs, which in ancient times required quite a bit of overshifting to change gears. But that was mostly due to the spiral wound chrome housing that came with most of it as original, which is wildly compressible, and is not real user friendly in terms of a positive shift. On those, even regular spiral wound housing is an improvement