Originally Posted by
spclark
Yeah, I've messed with it enough to be aware of that limitation.
Dyneema's a different critter, slippery as all heck but reacts to heat a lot like nylon and polypropylene.
(Google's reply to my query)
I've formed 'stoppers' on some stuff I've done with it with a torch & concave mould; it takes some unusual efforts to get knots that'll work.
All the typical cable heads I've ever handled looked to be cast-in-place, not unlike soldered, usually what looked like a zinc or aluminum alloy material.
I think you'll find those cable heads are steel if you try to file them.
Forming a knot in rope decreases the tensile strength by as much as 50%. Steel is exceptionally strong by volume, and shift cables are limited by size, not weight. So you could certainly make a Dyneema or Kevlar bike cable system, but it probably would not be compatible with existing shifters.