BB cable guides
 

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?

If you are worried about rust there you can use a small piece of plastic cable tubing to protect the paint. Not sure why they didn't run the tubing on both cables here but think you will get the idea...

http://www.uscoles.com/bikepix/nameonbottombracketl.jpg

That is what I did on my frame but the sleeves move over time and end up in the wrong place and doing nothing.

Also from experience - in my younger days when I still went out in the cold - the tube can get water in, freeze and hamper gear changing.

I haven't got a problem with this art all, just wondered.

Helicopter tape?

over the BB cable guides were made in steel, long ago..

No you're not missing anything except to stress over a detail that's pretty minimal. I've done the brazed on cable tubes thing for a few decades and excepting once with a neglected galvanized cable and an electrolyte drink spillage have never had any issues with cables, corrosion or friction. However I, too, stress over tiny stuff (or why would I make my own frames:)) and will likely go to plastic bolt on guides in the future. Here's a shot of such a set up that I made in 1985. Andyhttps://cimg4.ibsrv.net/gimg/bikefor...03a9d67cf1.jpg

When I add brazed-on cable guides, they're either brass or stainless. Carved up to allow for any water to drain out, rust has never been a problem.