Di2 Wiring help

[CrankAddictsRich]

Hey guys... I'm trying to pre-plan some Di2 wiring for a Shiv TT build and I was hoping that some guys with Di2 experience might be able to help me as I have no prior Di2 experience.

Here's the wiring scheme i've come up with.



I bought a very lightly used 6870 Di2 TT set up. Based on the picture, it appears that it comes with a shifters, FD and RD that I've labeled in the photo above. It looks like it also has a 5-way junction box and a JC-41 internal junction box. My plan was to hide the 5-way junction box internal just inside the head tube, along with one of the new BT/Ant + D-Fly boxes. I was going to drill a small hole in the tope of the seat post and mount a 3-way junction box under the saddle so that I could re-charge. Will this work? Thanks in advance guys.

[djwalker]

I don't think that you are allowed to have two EW-90's (A and B) in the system at the same time. I haven't tried it myself but none of Shimano's charts or manuals say that it will work. You could use a pair of EW-JC41's or EW-JC130's to combine the shifter wires into a single wire in the downtube. The JC41 is small enough to fit inside of bars and bar extensions (I have done it) so they can be hidden. The other thing to consider is that the 6871 wires are permanently attached to the lever so if the length is wrong you will need additional wires and junctions. Take a look at the attached file which is an excerpt from the technical manual.

[CrankAddictsRich]

I don't think that you are allowed to have two EW-90's (A and B) in the system at the same time. I haven't tried it myself but none of Shimano's charts or manuals say that it will work.

Hmmmm... good info. The thing that made me think it would work was that I read a post from a guy that said he kept a spare EW-90A and 300mm cable and he'd plug it into his RD to charge the system.

You could use a pair of EW-JC41's or EW-JC130's to combine the shifter wires into a single wire in the downtube. The JC41 is small enough to fit inside of bars and bar extensions (I have done it) so they can be hidden. The other thing to consider is that the 6871 wires are permanently attached to the lever so if the length is wrong you will need additional wires and junctions. Take a look at the attached file which is an excerpt from the technical manual.Di2TT Wiring.JPG

I wasn't aware of that aspect of the 6971 shifter levers. Hopefully they'll work, if not, I may be forced to run some of the system external.

[kode54]

have you explored the idea of using the new 'Y' cables? you can avoid using multiple junction boxes.

[CrankAddictsRich]

have you explored the idea of using the new 'Y' cables? you can avoid using multiple junction boxes.

No, I didn't realize such a thing existed... hmmm.

[kode54]

new for this year/season. cleans up some of the wiring.

[kode54]

did a quick search and this came up...

https://glorycycles.com/shimano-di2-ew- ... e-harness/

[djwalker]

You could use a Y cable to connect the buttons in the extensions. That, plus the two wires from the brake/shift levers and one wire in the down tube would fill up a single JC41 and should work fine. If the shift/brake wires are too short you can use a coupler and extension wire like is shown in the drawing I attached above.

I think that a second EW-90 might work for charging but I don't know if it would allow shifting to work because both EW-90s would be trying to do the same functions- mode select, adjustment, etc..

[goodboyr]

It will work for charging only. You just can't run the system with it in line. (shifting, adjustment, mode selection etc.)

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[CrankAddictsRich]

Maybe this is a better solution... just using an extra cable and a-junction in the RD to charge. Then I'd just have to figure out what's going on inside the bars to get the cable to each where I want them too.

[DeeHubbs]

When your A-Junction is inside the frame, you will be unable to micro adjust the FD or RD, take the system out of crash recovery mode, or toggle between your preset synchro shift programs.

[CrankAddictsRich]

When your A-Junction is inside the frame, you will be unable to micro adjust the FD or RD, take the system out of crash recovery mode, or toggle between your preset synchro shift programs.

I won't be using synchro shift, so that isn't even a concern at all. As I said early, I'm new to Di2 so I don't know all of the ins and outs, but isn't the micro adjust really just used during set up? Once the bike is setup, is there really a need to micro-adjust? Not really sure about crash recovery mode...

[jorisee01]

Or you cold just split the cables and connect them and cover them with isolation tape or something. Save some weight too. And probably some money.

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[Pokerface07]

You could use a Y cable to connect the buttons in the extensions. That, plus the two wires from the brake/shift levers and one wire in the down tube would fill up a single JC41 and should work fine. If the shift/brake wires are too short you can use a coupler and extension wire like is shown in the drawing I attached above.

I think that a second EW-90 might work for charging but I don't know if it would allow shifting to work because both EW-90s would be trying to do the same functions- mode select, adjustment, etc..

Y-cables won't work. Both the extension shifters and brake lever/shifters for TT have cables hard-wired in already.

[Pokerface07]

You can do it, but you'll just need to use more B-junctions to connect the front shifters to the A-junction under the saddle.