I recently got a new time trial frame and I am in the process of transferring my components from my old frame to the new one. My old frame (Cervelo P3) has an internally routed rear brake cable. Near the rear end of the top tube, the cable exits the frame through a little insert that fits into the cable hole. The insert slides into the hole, then the cable housing and ferrule slides into the insert. There is a small hole for the cable, and the ferrule sits against the back of the insert preventing it from slipping into the frame.
My new frame came with similar inserts... but oddly enough, there is nothing in the insert for the ferrule to rest against. First time I squeezed my rear brake lever, the ferrule and housing just sucked into the frame through the insert. I've looked at this and scratched my head for a few hours and just can't seem to figure out how this is supposed to work.
So as you see in the attachment, the ferrule is in the insert... but I am sure over time it will work it's way into the frame, just like the rear one. Any ideas? I'm sure I must be missing something simple.