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Di2 Alfine E-tube Savings and Shortcut

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Di2 Alfine E-tube Savings and Shortcut

Old 05-10-21, 01:58 AM
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Di2 Alfine E-tube Savings and Shortcut

Did I find savings and a shortcut? I'm buying parts to replace the existing IGH transmissions on two bikes. The new stuff is Shimano Alfine IGH with Di2 shifting. My setup has only three electronic elements: gear indicator display/pushbutton shifter on handlebars, battery mount, and the shift motor. Shimano suggests I buy a simple four port junction box (no fancy button) and three separate wires to connect my devices together. However, I wonder if I could use the T-shaped wire harness (EW-JC130) they sell for connecting elements on Di2 derailleur bikes. That harness has three E-tube plugs, and I have three things to plug into. I've measured, so I know I have to splice some wire into one too-short branch, but otherwise everything lines-up. Savings would be $50 x2 bikes, and no blocky junction box to hide. I assume there is no magic to the junction box and it could be deleted as I suggest. Might this work?

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Old 05-10-21, 11:10 AM
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Originally Posted by rvtraveller View Post
I assume there is no magic to the junction box and it could be deleted as I suggest.
That "junction box" contains flashable Firmware. I'm unsure as to why, but it appears to be more than a dumb "Y" connector.

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Old 05-10-21, 11:27 AM
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Originally Posted by Barry2 View Post
That "junction box" contains flashable Firmware. I'm unsure as to why, but it appears to be more than a dumb "Y" connector.

Barry
Hello, Barry. Thanks for your reply. The junction box I would use is the SM-JC41 (SM-JC40 as alternative). Unlike some Di2 junctions, the JC-41 and JC-40 have no buttons or any obvious function beyond tying the wires together. I don't understand why they would need circuitry in there.
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Old 05-10-21, 11:36 AM
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"Dumb Junction Box"

Moments ago, I found the reference below at bettershifting.com, so I'm still hopeful. Anyone else have thoughts?

"Junction A: The junction box at the front of the bike. Either below the stem, handlebar drops or the downtube. Usually a display on mountain bikes. Has a button, LEDs and a charging port.

Junction B: A dumb junction box that connects the rear (FD, RD, battery) to the front of the bike. Basically a 4 way splitter. SM-JC41 is the internal version, SM-JC40 the external one."
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Old 05-10-21, 12:25 PM
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It'd probably help if you gave the Shimano part numbers of everything you are asking about. What some of us consider a Junction box might not be your idea of a junction box.

You have this? https://si.shimano.com/api/publish/s...001-12-ENG.pdf

It might not be for your model, but there are others available at https://si.shimano.com
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Old 05-10-21, 02:19 PM
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Proposed part numbers for Di2 system

These are the parts to be connected:

MU-S705 - motor unit at IGH transmission

SM-BMR2 - mount for external battery

SC-S705 - gear indicator display (attaches independently to SW-S705 shifter switch)

The (dumb?) junction to be considered is SM-JC41. It has no buttons or lights. I think that junction is probably a simple splitter device.

The "T"-shaped EW-JC130-MM Shimano wire has three plug, and I have three devices to connect.

I've studied the manual that Iride01 linked. It led me to ask if that junction box was necessary.
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Old 05-10-21, 03:10 PM
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Originally Posted by rvtraveller View Post
I've studied the manual that Iride01 linked. It led me to ask if that junction box was necessary.
So the Y-cable you mention was specifically developed for drop bar bikes that use a bar end junction A, as opposed to the original style that is hung from the stem. In theory you could use the Y-cable. But, lets go back and review your set up...

Currently you need to get 3 items linked together. The most expeditious and easiest way is to use either a SM-JC40 (external) or SM-JC412 (internal) as Shimano describes in that manual you referenced above, and use 3 eTube wires EW-SD50 of the appropriate lengths to connect each component to the JC40/41 to build the system.

If you want to use the EW-JC130 Y-cable first you need ensure to get one long enough to at least get two of the components links, and you only need to worry about the end that is quite short at 50mm (about 2 inches). To extend that short cable end, you'd need to get an EW-JC200 junction and an EW-SD50 cable of the proper length to make that short end reach. No idea on the pricing, but in the end, it may not save you much, and it may be simpler to just build you system according to the diagrams in that manual you've already studied. Also, I've never heard of anyone using a Y-cable to do anything except connect an EW-RS910 junction box at a bar end.

Good luck!
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Old 05-10-21, 09:47 PM
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Thanks, Badger6

Thanks for your reply, Badger6. I can't auto-quote you here yet because I need to log more posts per the forum rules. But, I've copied your comments below my reply.

I've measured everything. The 550/50/550 (mm) version will serve the motor unit and battery mount perfectly. I'll need to lengthen one 550mm leg to reach the display/switch on the handlebars. I've confirmed there are only two wires inside the cable, so a secure and almost invisible splice is easy (for me). I have two-wire round cable of suitable dimension from years of cast-off A/C adapters and such. Cost savings would be at least $50.00 USD per bike. My wife and I have identical bikes, so $100 USD savings. I'm paying pandemic prices for these parts, so any savings are appreciated. My exterior wiring would be sleeker, too, without the junction.

[QUOTE BADGER6]

So the Y-cable you mention was specifically developed for drop bar bikes that use a bar end junction A, as opposed to the original style that is hung from the stem. In theory you could use the Y-cable. But, lets go back and review your set up...


Currently you need to get 3 items linked together. The most expeditious and easiest way is to use either a SM-JC40 (external) or SM-JC412 (internal) as Shimano describes in that manual you referenced above, and use 3 eTube wires EW-SD50 of the appropriate lengths to connect each component to the JC40/41 to build the system.

If you want to use the EW-JC130 Y-cable first you need ensure to get one long enough to at least get two of the components links, and you only need to worry about the end that is quite short at 50mm (about 2 inches). To extend that short cable end, you'd need to get an EW-JC200 junction and an EW-SD50 cable of the proper length to make that short end reach. No idea on the pricing, but in the end, it may not save you much, and it may be simpler to just build you system according to the diagrams in that manual you've already studied. Also, I've never heard of anyone using a Y-cable to do anything except connect an EW-RS910 junction box at a bar end.

Good luck!

[END QUOTE BADGER6]
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Old 05-10-21, 11:23 PM
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Originally Posted by rvtraveller View Post
Thanks for your reply, Badger6. I can't auto-quote you here yet because I need to log more posts per the forum rules. But, I've copied your comments below my reply.

I've measured everything. The 550/50/550 (mm) version will serve the motor unit and battery mount perfectly. I'll need to lengthen one 550mm leg to reach the display/switch on the handlebars. I've confirmed there are only two wires inside the cable, so a secure and almost invisible splice is easy (for me). I have two-wire round cable of suitable dimension from years of cast-off A/C adapters and such. Cost savings would be at least $50.00 USD per bike. My wife and I have identical bikes, so $100 USD savings. I'm paying pandemic prices for these parts, so any savings are appreciated. My exterior wiring would be sleeker, too, without the junction.
There are definitely some reports of folks splicing wires on the internets, but, it's an approach I wouldn't recommend. Reputable shops probably won't touch it after you do that, and Shimano will most certainly decline to honor any warranty. If you have further issues you'll be on your own, and probably right back here asking for help...please make sure you clearly state you modified the wiring harness/loom with splicing so we can then decline to offer any additional help because once the wiring is cut into, who knows. Sometimes saving a few pennies will ending up costing a few pounds. A lesson I've learned the hard way more than once because I am stubborn.
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Old 05-11-21, 11:43 AM
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I dont think the harness is truly waterproof, therefore, as long as the splices are done well I'd try it. if it has an IP rating of 67 or better, I'd opt to buying the harness.
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Old 05-11-21, 01:10 PM
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Reply to Troul:

Thanks for your reply The 3-plug harness is a Shimano part. It has the same connectors and cable as the straight wires, so I don't expect any more problems with water than using the more conventional parts. In fact, it reduces the number of connections from 6 to 3, so it should be more water resistant than the typical parts. My splice is easily waterproofed.

[QUOTE TROUL]

I don't think the harness is truly waterproof, therefore, as long as the splices are done well I'd try it. if it has an IP rating of 67 or better, I'd opt to buying the harness.

[END QUOTE TROUL]
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