Internally Routed Shift Cable Replacement

[Tony S]

So I have a new-to-me bike and I need to replace the front derailleur cable. It's the first time I've had to do this on a bike with internal routing. The cable enters the frame at the top of the down tube, exits briefly under the BB, where it routes OUTSIDE a removable insert, re-enters the same hole and emerges through a much smaller hole at the top of the BB, whence to the derailleur. Of course after futzing around too long I ended up with the cable out of the frame.

Anyway, it looks like the key to threading the thing is that the large insert under the BB has to come out. However, the well-adjusted rear shift cable routes around the same insert. So my question is, is there some trick to removing the insert and replacing the FD cable without having to undo the RD cable (and possibly be forced into replacing it, too) at the same time? Bike is a 4yo Cervelo R3.

 

[wooglin]

Time for a new bike. Sorry.

 

[Tom K.]

I know service departments everywhere are backed up, but I'll just say that I'm a damn fair bike mechanic, and internal cable replacement is one of two things that I cheerfully pay the LBS to do for me.

Not because I can't do it.....but because the lead mechanic has done so many that he has the "touch".

Or maybe it's time for AXS?!

 

[Erik Timmerman]

 

[Tony S]

I'll get some pics up.

 

[crgildart]

Here's me finishing up my DIY internal cable repair..

 

[scott43]

I've never worked on a Cervelo before..but...it may be possible to get some rear der tension relief..if you shift to the top cog in the back, stop pedaling, and then shift down with the rear shifter while pulling the cable manually you might get enough slack to either disconnect the rear der cable from a cable stop (to get more slack..) or to at least get done what you need to do without having to disconnect the cable and mess that up. Beyond that I think you're looking at using a spoke or some other hook to try to pull it through without messing about too much.

 

[cantunamunch]

I know service departments everywhere are backed up, but I'll just say that I'm a damn fair bike mechanic, and internal cable replacement is one of two things that I cheerfully pay the LBS to do for me.

Not because I can't do it.....but because the lead mechanic has done so many that he has the "touch".

As I intimated in my previous thread on this topic, I am convinced that most LBS seriously undercharge the customer for this work.

And yeh, I'm totally going wireless, - for the gr dropper at least.

 

[gwasson]

So I have a new-to-me bike and I need to replace the front derailleur cable. It's the first time I've had to do this on a bike with internal routing. The cable enters the frame at the top of the down tube, exits briefly under the BB, where it routes OUTSIDE a removable insert, re-enters the same hole and emerges through a much smaller hole at the top of the BB, whence to the derailleur. Of course after futzing around too long I ended up with the cable out of the frame.

Anyway, it looks like the key to threading the thing is that the large insert under the BB has to come out. However, the well-adjusted rear shift cable routes around the same insert. So my question is, is there some trick to removing the insert and replacing the FD cable without having to undo the RD cable (and possibly be forced into replacing it, too) at the same time? Bike is a 4yo Cervelo R3.

The trick is there is a thin cable guide that you thread over the old cable from the bottom (derailleur side) until it comes out the top of the frame. Then you pull the old cable out and thread in the new cable. So it's really not that hard to do as long as you have the cable guide.

I think it is pretty much a pain without the cable guide.

 

[Tony S]

The trick is there is a thin cable guide that you thread over the old cable from the bottom (derailleur side) until it comes out the top of the frame. Then you pull the old cable out and thread in the new cable. So it's really not that hard to do as long as you have the cable guide.

I think it is pretty much a pain without the cable guide.

Very concrete. Thanks!

there is a thin cable guide

There is? Is it on my workbench? In my back pocket? Where is it?

 

[Philpug]

I know service departments everywhere are backed up, but I'll just say that I'm a damn fair bike mechanic, and internal cable replacement is one of two things that I cheerfully pay the LBS to do for me.

Not because I can't do it.....but because the lead mechanic has done so many that he has the "touch".

Or maybe it's time for AXS?!

Plus the need for all the proprietary tools that sometimes are required.

 

[gwasson]

Very concrete. Thanks!



There is? Is it on my workbench? In my back pocket? Where is it?

You can ask the LBS for one. I think they come with every new bike, so my LBS gave me guides when I went in and bought replacement cables. If you are doing the rear derailleur, you need 2 guides, assuming the cable routes through the rear chain stay.

Edit:

I mean to say, they are installed in the frame and then the shop threads the cable through them when building the bike. Most likely they save a few so they have them on hand when replacing cables. I am sure the experienced guys can do it without the guides, but it makes it much easier.

 

[gwasson]

Here is a nice hack that might help.

 

[Ross Biff]

I know the infernal cable routing of which you speak! It's not the worst set up out there but no internal cable changes are fun. Just be thankful for the huge reduction in aerodynamic drag you get!!! The cable guides spoken of previously ( we call 'em noodles or spaghetti) are very useful so put them somewhere safe if you get your hands on some from your LBS.

 

[Tony S]

Hey everyone. Thanks for all the help. I got it done last night. Really wasn't so bad. (It actually took me longer to figure out how to get the cable head properly seated in the new-to-me shifter body than to thread the stupid thing.)

Basically I just followed the suggestion from @scott43 . Removed the RD cable from its anchor bolt carefully without stripping off the crimp at the end. This provided just barely enough slack for to get the BB insert out of the frame far enough to fish the new FD cable with the help of a flashlight and long tweezers (see pic). Once I had it, step two was taking the piece of spaghetti (@Ross Biff , @gwasson) skulking quietly in the down tube and threading it from the big BB opening up through the small hole in the top of the BB shell immediately below the FD anchor bolt. Ran the cable through the spaghetti and Bob's your uncle.

View of BB insert in operational mode:

BB insert partially removed with newly fished cable visible:

Key tool:

 

[zircon]

Piggybacking on this thread. Any Trek owners and mechanics have thoughts and opinions on recabling an Emonda? On a scale from "annoying weekend job" to "get on the LBS waiting list and tip them double" how much of a PITA is it going to be?