I have a custon built frame with brazed on cable guides under the bottom bracket. At the time it seemed like a good idea, the builder certainly thought it was a step up from the basic moulded plastic cable guide.

As an Engineer, a steel cable running in plastic ((I assume it is nylon or similar) is a much better engineering solution than one running on steel. Add a paste of mashed paint and a bit of rust that will develop in the steel guides over time and they seem even less of a good idea.

Having said this I have had no problem with my custom frame, I just cannot see the point of brazed on steel cable guides under the bottom bracket.

Am I missing something?