Installing front derailleur cable through BB

[ontarget]

My front derailleur cable is beginning to fray, so I need to replace it. I've never done this on this particular bike before, and have a question for you all before I screw something up.

The cables are externally routed. The FD cable runs on the bottom side of the downtube, through a guide on the bottom side of the BB, through a hole in the bottom side of the BB area, then out a hole in the top side and to the derailleur. The portion going through the BB area looks like a straight shot. Should I expect to be able to just insert the new cable without much fuss, or do I need to attach a string to the old cable to use for pulling the new cable through? Or some other technique?

Thanks!

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[AngryScientist]

what bicycle are we talking about here?

a picture of the BB area would totally help...

[Blown Reek]

If it's external and your bottom bracket guide looks like this,



then all you have to do is route the cable. No other tools or tricks necessary. Easiest thing to do in the world.

[eddief]

I had a Spec Roubaix where the channel through the bb was a bit clogged up. I think there was a plastic tube through which the cable had to pass. It took a bit of "jamming" of the cable to clear the path. But I'd guess if when you take out the old one and if it comes out smoothly, then inserting the new one should go smoothly too.

[seanile]

could look like this, in which case you want the little plastic tubies

[ColonelJLloyd]

If it's like the Merckx you can rob the lining from sold old housing by dissecting carefully with a razor blade.

[zmudshark]

If it's a straight shot, it's a straight shot. Should be easy-peasy.

[ontarget]

Sorry for the lack of photos previously. Here are a couple quick ones I took as I was heading off to work this morning.

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[icepick_trotsky]

I think you just poke that through as is and cross your fingers.

[David Kirk]

Start with a brand new uncut cable so that it's soldered closed on the end and this will allow you to poke and jab it through without worry of it fraying. Then once you get it all set up cut it to length.

dave

[Blown Reek]

Originally Posted by icepick_trotsky

I think you just poke that through as is and cross your fingers.

Originally Posted by David Kirk

Start with a brand new uncut cable so that it's soldered closed on the end and this will allow you to poke and jab it through without worry of it fraying. Then once you get it all set up cut it to length.

Yes and yes. Poke gently.

[ontarget]

Thanks for the feedback, everyone. Much appreciated!

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[dustyrider]

[Mark McM]

That's an awfully sharp bend where the cable enters the BB shell - not a particularly well executed design. While I'm sure it can work at some level, the derailleur cable can easily get a kink at the bend, hampering the shifting performance a bit. Not to mention that if you shift the front derailleur a lot, the cable may slowly saw its way through the BB shell.

What brand/model bicycle is this?

[Hilltopperny]

I took a pipe cleaner and threaded the cable through it and through the frame on my internally routed bike. Before I figured that out it seemed impossible.