Tips for running internal RD cable in Giant TCX?

[Veloo]

Neighbour is asking for some help to swap out a portion of housing on his Giant TCX. Not sure what year it is but pic attached.
Lever is SRAM Apex.

It's not going down to the smaller cogs.
He said the shop swapped out all housing and cable except for the housing from the lever to the downtube. From what he described, they had to fiddle quite a bit at the LBS to get the cable fully routed through.

As an external cable guy, this doesn't sound like a pleasant task. Anyone have tips on how to facilitate the routing cable from the downtube back to the RD?

[gravelreformist]

Use the existing housing to pull the new housing through.

The Park internal cable routing kit is crazy expensive for what amounts to some wire, magnets, and special ends, but it can easily pay for itself in the amount of time it saves just setting up one bike. Routing di2 and brake cables through a set of aero handlebars recently would have been nigh on impossible without it.

[benb]

On a carbon frame you don't even need something like the Park kit.

You just need a decent magnet which you can find at any toy store or if you have an old hard drive, VCR, etc..

Be careful not to scratch the finish but just insert the cable and run the magnet along the outside of the frame and the cable will follow along.

This works so well I never actually use the park kit I got, but the Park kit probably works in some edge cases that nothing else will work in.

This assumes cables inside the frame without housing, but housing often runs through a channel and it's so stiff it usually behaves a lot better.

[Mark McM]

Since he mentioned "housing from the lever to the downtube", that implies that there is a housing stop where the cable enters the downtube, and then bar cable runs inside the frame. In these cases there needs to be a cable guide at the bottom bracket.

Sometimes the cable guide is external to the BB shell, which means that the cable has to exit the frame at or near the BB shell, run through the external cable guide, then either re-enter the frame to run through the chainstay, then exit it the chainstay and run through another piece of housing to the derailleur.

Occasionally the cable guide is internal the BB shell, which case there needs to be access to the inside of the shell in order to thread the cable through the guide. This access might be through a cover or plug in the bottom of the BB shell.

There are also some bikes in which the housing from the shifter continues into the downtube, all the way to a cable stop in the bottom bracket cable shell.

So you'll have to start by 1) first determining whether the cable is run bare through the frame or if the housing continues into the frame; 2) if the cable runs bare through the frame, you'll have to determine whether the BB shell cable guide is internal or external, and how to access the cable at the BB shell; 3) or if the housing continues into the downtube, whether the housing stops at the BB shell or continues all the way through the frame and out the chainstay to the derailleur.

Once we know these things, we can probably give some more advice as to how the fish the cable (and/or housing) through the frame.

Many bike manufacturer websites have bike manuals which will give instructions on routing cables. You should check to the Giant web site to see if they have a downloadable manual for this particular bike. If it is an older model, there may be archive of manuals for discontinued models on the Giant web site.

[benb]

The TCX is still Giant's current Cross bike AFAICT.

Info should be easy to come by.

[Wunder]

Everything Mark said is correct. For my Cervelo R3 that is internally routed with stops on the downtube, an under BB guide (removable which makes this job easier), another stop at the chainstay, and bare cable through the frame I have some hollow PTFE tubing with a 2mm inner, 3mm outer diameter.

I remove the rear housing, slide the PTFE tubing over the cable BEFORE REMOVING IT, until it pops out below the BB, pull back the cable until exposed, then slide another tube up to the housing stop. I use these as guides to thread a new cable and then remove them. I probably have some pictures I can supply later. With this method it's an extra step, but not really any harder than an external cabled bike.

Tubing like this. I have three, each in 1 meter length.

https://www.ebay.com/itm/39505055294...3ABFBMltrV79lj

[JSL]

These can be a bit tricky.

The clear inner housing doesn't continue from the handlebar to the derailleur. There's a separate short piece through the chainstay on most frames from the factory(fed in from the rear) and it's often impossible to make the connection between the hoses.

You'll most likely have to remove the BB unless you're very lucky. Afterwards, I use a burner piece of clear housing (longer than you will ultimately use on the frame) fed in from the rear to the BB exit port. Make the connection with the wire there, guide the wire through the chainstay and then replace the burner housing with the correct piece.

I do it this way because it's extremely tricky to feed anything from the BB end through the chainstay on these due to the placement of the exit hole, glue, etc.

Sounds more complicated than it really is. Just takes patience.