Merckx Corsa Extra internal cable routing

I've invested in a beautiful new Campagnolo cable set but the rear brake cable has too much friction through the internal cable route in the top tube so the calliper's not releasing.

Only the inner cable passes through the very small cable route hole. I've tried cleaning out the channel with teflon spray but still a friction noise through the tube. The Campagnolo brake cable inner is quite thick so I wondered if a thinner inner would work or perhaps there's some other trick to it? Any ideas gratefully received!

Thanks all, Jon

Cable

Hi Jon
I use Shimano cable on my corsa extra and the outer cable goes straight through. Its a perfect fit, snug enough so it doesnt move.

Jamie

Thanks Jamie,

I think my Corsa Extra frame is slightly different, the recessed cable hole is not more than 2.5mm diameter. I guess your frame has a larger hole to enable you to feed the Shimano sleeving all the way through? Wish mine was the same!

Had another go with last night with more spray lube and pulled an old length of frayed cable through a few times in case there's any debris in the tube. Actually a little bit of rusty stuff came out but I think it's quite clean now.

Tried the rear brake again but the cable is still not running freely.

The Campagnolo brake cable inner is 1.8mm in diameter so after a bit of investigation I've decided to try some Jagwire brake inner which I believe to be thinner at 1.4mm. It might be enough to stop it snagging.

As another idea, I see some of the funky alternative cable systems like Alligator ilink etc have a removable inner lubed sleeve which might fit through the hole if I'm lucky?

If anyone else has overcome this problem with an internally routed brake cable in the top tube, please lend me the benefit of your experience!

Cheers all

Jon

Mine has the outer cable through the top tube, but I would suggest:

Use ferrules on the end of the cable where it contacts the top tube, so that the inner goes into the tube in a straight line.

Fit the plastic lining onto the bare inner cable inside the top tube.

Thanks all, I got some stepped ferrules. For 5mm brake cable outer stepped down to 3.7mm outer diameter to fit into the frame.

It was a little loose so I wrapped some heatshrink sleeving and some electrical tape to make the ferrules fit snug.

Anyway bike built now and rear brake working!

cheers for the advice

Jon