The rear brake cable and housing are internally routed through the top bar of the frame. It rattles around when riding on bumpy roads and sounds annoying. What's the best way to mitigate this?
With the assumption that the whole cable housing is threaded into the frame (rather than cable-stop internal routing), there are two main hacks/bodges you can do to it.
- Electrical tape - fiddle with the cable until you feel that it's more or less either floating in the middle of the frame's tube or resting against it with sufficient force. If your frame tubing's fairly narrow (kind of like a steel bike frame), I suggest you go for the latter and push the routing against the frame inside. Mark the points of the cable housing just on the entrance/exit of the routing holes. Roll a few turns of electrical tape on those marks (just enough for tight-fit on the routing holes) and push them back to place.
- Cable/zip ties - If your frame's routing holes are big enough, or has that detachable cover like this:
you can wrap a lengthy zip tie to the cable and slip it inside the hole. The zip tie's resistance to being curled should keep your cable in place. Add more zip ties to your discretion.