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Internal routing question: two cables, one hole?
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Hi, I helped a friend build a road/gravel-ish bike from the frame up (his first bike, $1,000 budget, frame bought due to bike shortage, etc.). The frame seems to be, oddly, designed to be built as a 1x, so it only has internal routing holes for the rear derailleur and a rear disc brake cable. This is surprising because it makes building a 2x difficult.

Question: Does anyone have any solutions for routing two cables through one internal routing hole? I could try running both derailleur cables through one, or the brake and front derailleur cable through the slightly larger brake hole. Perhaps there are ferrules or stops that make this possible.

- Frame is a Marin Gestalt 3 (2017) (viewable here: https://www.marinbikes.com/...bikes/2017-gestalt-3)
- The build is 2 by 10 speed Shimano 105, compact crank, mechanical disc brakes.
- I know there are ways to route a cable externally (using zip ties, or Problem Solvers brand cable stops etc.).
- Ultimately I may convince him to go with a 1-by setup.
- I know there's the $1000 solution with SRAM wifi or Di2, but those are way out of budget and his knowledge as a beginner rider.

Thanks for any info or ideas you have. I know there might not be a perfect solution, but I do know that Slowtwitch is one of the most knowledgable places for asking!
Last edited by: AG Tri Newbie: Sep 2, 20 9:28
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Re: Internal routing question: two cables, one hole? [AG Tri Newbie] [ In reply to ]
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Might be helpful to say what make/model the frame is??
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Re: Internal routing question: two cables, one hole? [s.gentz] [ In reply to ]
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Totally! Sorry – edited above, and - Frame is a Marin Gestalt 3 (2017) (viewable here: https://www.marinbikes.com/...bikes/2017-gestalt-3)
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Re: Internal routing question: two cables, one hole? [AG Tri Newbie] [ In reply to ]
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The bike is made for 1x. That's all there is to it.
You might get lucky with some hack to get a cable to route internally but doubt it will ever work well.
External- is the BB drilled for a cable guide to go up to the FD? If not, are you going to tap a hole for the cable guide?
Can the frame even accept a front derailleur?
It looks like the Gestalt range uses the same(ish) frame throughout and the Gestalt 1 was sold as a 2x bike, so you might be in luck with the drilling and using a standard diameter clamp on FD.
External housing stops can be had, but the downtube of that bike is almost certainly some non-standard roundness and finding a clamp on housing stop in the right diameter could be a challenge.

It would be much easier and far less hassle to just go 1x.
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Re: Internal routing question: two cables, one hole? [ayontz] [ In reply to ]
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Yeah I totally agree on all your points! I'm guessing 1x will be the eventual solution, especially when he realizes that it works very well. I'll help him figure out a 10 speed cassette and perhaps a rear derailleur hanger to increase his range. He is nervous about having enough gears for hills, and this is his first "real" bike, so even Shimano integrated shifting is mind-blowing (a paradigm shift...?) for him – in a good way.

- There is a hole for the plastic Shimano derailleur cable guide piece to screw into, so that's no problem.
- I installed a clamp for the front derailleur and had it all set up. There is room for the front derailleur cable to turn up to meet the front derailleur, like on traditional bikes.
- I wasn't able to get a good stop for the front cable where it enters the frame (I initially jammed it in alongside the brake cable, but without its own ferrule/grommet).
- You are right on the tube shapes – kind of oval. I think stick-on / zip-tie-on ones might work, but aren't great looking.

I really appreciate your help! I've been scouring the online catalogs of Jagwire, Problem Solvers, etc. too, and even went to Lowe's in search of random electrician pieces that might be of use.
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Re: Internal routing question: two cables, one hole? [AG Tri Newbie] [ In reply to ]
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I would buy a different frame.
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Re: Internal routing question: two cables, one hole? [AG Tri Newbie] [ In reply to ]
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I would guess using zip ties or adhesive would be a disaster.
There is no way that they would be secure enough to ever have a FD shift correctly.
You need something that will not move at all when a substantial amount of force is applied to it. Just try moving your FD with your fingers. Then imagine that force applied to a zip tied housing stop.
That's why all the Problem Solvers and such are clamps. You can tighten the snot out of them and they won't go anywhere.
Housing stops exist that you rivet on, but really?

Pull out a gear chart and show your friend that a 42t front with a 11-42 out back will actually give him a easier set of gears than a 50/34 with a 12-28.
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