Inside this sheath runs a brake hose and a thin wire. Unfortunately on my bike I have 12cm of wrapped insulation tape instead, which is untidy and unravels.

It'd be a huge job to remove everything and slide a sheath on.
Is there some wrap on style heatshrink, or a superior tape, that would do a tidy job of it?
Self amalgamating tape might do a neater job, it'll define stay on better.
I've used those crimp/spiral hair bands that I found in the pavement and cut in half. Wrapped around two cables it stops them from clattering around.
I'll try that tape.
I believe the original sheath was too tight for 5.5mm Hayes hose and the cable.
I used this, did a decent enough job https://www.screwfix.com/p/self-amalgamating-rubber-tape-black-3m-x-25mm/2115v
Not enough room to wrap, so I used several pieces fitted perpendicular to the hose, each overlapping slightly with the next.
Then Kintsuglue (Sugru) to fill the ends where it goes into the frame.
Spiralwrap as above (1st choice), or self amalgamating tape depending on contents of toolbox.
Both are worth having anyway, sort of things that are cheap and just the right thing for certain jobs.
I didn't go for the spiral wrap as I wanted them fully enclosed.
Spiral heatshrink or spiral self amalgamating tape would be ideal, that is if such things were possible.
At the risk of stating the obvious, surely “spiral tape” is just straight tape wrapped into a spiral? (Like bar tape)
Heat shrink tape exists, but it seems expensive compared to normal self-amalgamating tape…
At the risk of stating the obvious, surely “spiral tape” is just straight tape wrapped into a spiral? (Like bar tape)
I imagine it would come in a shaped form that makes it easy to screw onto something, like the rigid spiral stuff above.
I'm not sure heat shrink tape would have any particular benefit over self amalgamating.
How about…
Get some normal heat shrink tube and cut a length about twice as long as you need
Slide the tube onto the handle of a wooden spoon (or similar)
Use a sharp blade/stanley knife to cut a spiral along the complete length of the tube
Compress the resulting spiral (like a spring) so that you have an overlap for the tape to bond to itself
Apply heat…
It’ll either work a treat or fail spectacularly but if it’s the first, file a patent and then sell it to multinational tape corp inc…