Originally Posted by Fiemme
Instead of using brake cable housing try using the teflon inner of gear cable housing. This will allow the cable to glide easy and not rub on the metal frame.
I'm sure you can purchase the teflon tube as an independent item.
You can also use a plastic tube cover on the brake/shifter cable, like they do on the Nokon setups and no need to weld anything and save your paint (aka prevent rust). I'll try to find some.
Here it is: Nokon Cable Liner
If you cover the whole cable length you should cut a longitudinal hole or slice near the bottom to allow moisture to get out, or the cable will eventually rust. You can hot glue gun the liner to the bottom bracket guide or some other glue method if you are only using it at the bottom bracket. The liner allows the cable to move freely and shift/brake, just don't heat shrink it to the cable.