Originally Posted by
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.
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