Di2 Internal Junction Location

[ValleyForge]

Thinking about putting XTR Di2 on my XC bike - a carbon 2014 Cube duallie.

The cables run currently through the frame and exit just in front of the (press-fit) BB facing the ground. There is a smallish window here filled with a plastic block anchoring the two grommets.

I am wondering how big the Di2 Internal Junction SM-JC41 is and if it will fit through. Alternatively can it be shoehorned up the downtube via the BB shell?

[Duck!]

The JC41 box is roughly 25x15x8mm, give or take a couple in each dimension. That's before anything is plugged into it. The easiest way to fit it is to stuff it in through the bottom bracket once all the cables are connected. Just be careful to ensure the cables are clear of the moisture-sealing sleeve between the bottom bracket bearing housings when refitting the BB.

[ValleyForge]

Thanks Duck. The cable egress hole is 28 x 15mm so it might work. Just trying to keep as much internal as possible. The battery in the headtube option looks good, but not worth the added cost of a new stem & bars.

[Duck!]

Where are you thinking of mounting the battery?

I can't really see how the existing cable port would be of use anyway if you're trying to keep everything internal. That sort of arrangement is typically to integrate a guide for mechanical gear cables under the BB shell, and under the cover the hole into the frame cavity is considerably smaller. Plus you'd end up with at least one cable externally, which you're trying to avoid (I'm making the assumption here that the frame is already internally routed).

[ValleyForge]

Battery in the seatpost. Given the suspension, the wires need to come out somewhere and under the BB looks the best. Mostly I wanted to have the battery inside and avoid the external bidon junction box.

[Duck!]

OK. In any case, I still reckon the easiest way of getting the junction into the frame will be to take the cranks off & stuff it in through the BB - I've never seen a cable-exit port big enough to poke the junction box through. Where this could strike a problem is if the BB is a fully-enclosed sleeve with no access into the frame cavity. Depending on how the existing FD is routed you could possibly keep that internal, thus only needing to pop the RD cable out to pass the lower linkage.

[ValleyForge]

Both FD & RD will need to go out through the cable port as I can't see a clever way around it. I can now see why for most LBS it's easiest just to do it all external in an upgrade installation. Will probably do the cranks to going from XT to XTR Trail triple. In for a penny....

[Duck!]

Yeah, problem with Di2 being so new for MTB, it's a real trial & error thing to retro-fit neatly until more compatible frames come on stream from the manufacturers. Same deal it was for roadies 5 or so years back. Interested to see how you go sorting it out.

Is there the ability to run the RD cable through the chainstay? Would be a nice tidy setup if you can, just pop it outboard to get under the linkage. Setup tip for the RD in any case, fully depressurise the rear suspension so you can get the cable slack right to not be upset by full compression. Not allowing enough could have unwanted side effects.

[ValleyForge]

Thanks Duck - have seen someone use a compression strap to get the rear wheel through to full travel. Letting the air out would be easier. My LBS, I guess like most have limited retro-fitting experience. It is a bit of trial & error.

[Duck!]

Any progress?

[ValleyForge]

My tax refund hasn't arrived yet. But the accountant asked for an extra $4400.

And he doesn't want to barter for the near new XT drive train.