Ask a Mechanic: Internally Routed Cables

Today’s question came in response to the video above that I made on internal cable routing. 

Question: Unfortunately, I rushed into it and pulled the rear brake cable out of the frame before using a lining tube to reroute the new cable.  Now I’m finding it utterly impossible to reroute the new cable.  I have a BMC Team machine SLR01, which doesn’t accommodate the spoke wire method.  The enter and exit holes are quite tiny, and the new cable isn’t finding its way out the exit hole.  There’s hardly any space to fit anything else through the hole.  I think it might not even be so easy to reroute a lining tube through the frame so that I can pass the cable through that!

Any suggestions?  I’m at my wit’s end! From: JP

Answer: One tactic is to use a powerful magnet to draw the cable where you want it to go.

Another method that is more involved, but also more reliable is to attach a string or dental floss to the end of the cable and then draw the string through the frame and out the exit hole using a vacuum. The way that I prefer to attach the string to the cable is to take a cable crimp and then cut off the closed end and any funnel-like flange if there is one. Slide the crimp onto the end of the cable along with the string and then clamp down on the crimp like you normally would at the end of a cable install. This should hold the string tight to the cable so that it doesn’t pull off when the cable is pulled through the frame.

Check out this video we made to show how the process works:

Welcome to our Ask a Mechanic column where our expert mechanics Daniel Slusser and Greg O’Keeffe answer your bike maintenance questions. If you have a question for us, please post it on the Art’s Cyclery Facebook Wall or e-mail Daniel directly at To see more great how to videos click on the highlighted link to subscribe to our YouTube channel and stay up to date on each episode of the Art’s Cyclery/VeloNews Ask a Mechanic Series.