I have only had one cable fail in the past decade. I thought that I felt some sharp bits on fingers at my right side bar end shifter and I had to adjust the shifter a few times over the last dozen miles, when I got home I took a closer look.



Only three strands remaining, very little warning. If the sharp ends were not stabbing my fingers, it would have been zero warning other than sudden need to adjust shifter a couple times.

I carry a spare rear derailler and spare rear brake cable. I do not carry a cable cutter, if I need it I will wrap up the excess and tape it to something with electrical tape.