I did a Di2 upgrade to my Felt IA16 last weekend, and this has the project details. I am posting, because Di2 takes a lot of research and planning, and there was very little quality information posted about different approaches, essential components, wire lengths, etc. (The Shimano installation guides have everything you need, but they are also word vomit, so almost as bad as nothing.) I picked Di2 over eTap because the big Blip Box is difficult to hide and shows lots of wires no matter what you do. I achieved a much more hidden installation with Di2 than eTap, and I still have my Junction A fully accessible.
First, Shimano’s product managers should be scolded for making so much confusion from something that is relatively straight forward. The CAN bus has been around for decades. My last two cars were built around the CAN bus. I used to have a serial-to-CAN bus interface so I could monitor traffic on the bus. I understand it pretty well, and yet Shimano found a way to make it seem complicated.
Junction A and Junction B are bad names; they are stupid names. Junction B should have simply been called something like “Splitter Block,” “Wire Junction,” or “Wire Joiner.” That is all it is. It just splices E-Tube wires in parallel. It has no internal brains. Junction A should have been called something like the “Charging Port” or “Status Port.” That is what it is. That it also happens to have additional ports is immaterial. And the EW-JC130 should never have been called a Junction B. It should have been called a splitter.
This is key, because you can have as many Junction B ports in a bike as you want. They are just parallel wire splitters. However, a Junction A (not a junction) is a special interface that you must have exactly one.
I used the bar-end EW-RS910 Junction A in the end of my extension. That took some Dremel work on both the module and the inside of my extension to get it to fit. I got a good friction fit, so it requires no other tape to secure, and neither will it come out on its own. I also drilled a couple wire exit holes on my extensions near the back end of spacers so that I have a totally hidden wire path. The net result is that I have only one Di2 wire visible on the cockpit going from the stem into the frame.
Following are some summary bullets along with pictures of the Shimano topology I used along with a diagram of my specific design.
My parts list:
The forum only allows a few pictures per post, so I will follow with a few more posts with additional pictures. These are Shimano's topology that I used as reference, my specific design, and all the stuff I had to buy. Last is the finished cockpit with just the single cable going from the cockpit to frame.
First, Shimano’s product managers should be scolded for making so much confusion from something that is relatively straight forward. The CAN bus has been around for decades. My last two cars were built around the CAN bus. I used to have a serial-to-CAN bus interface so I could monitor traffic on the bus. I understand it pretty well, and yet Shimano found a way to make it seem complicated.
Junction A and Junction B are bad names; they are stupid names. Junction B should have simply been called something like “Splitter Block,” “Wire Junction,” or “Wire Joiner.” That is all it is. It just splices E-Tube wires in parallel. It has no internal brains. Junction A should have been called something like the “Charging Port” or “Status Port.” That is what it is. That it also happens to have additional ports is immaterial. And the EW-JC130 should never have been called a Junction B. It should have been called a splitter.
This is key, because you can have as many Junction B ports in a bike as you want. They are just parallel wire splitters. However, a Junction A (not a junction) is a special interface that you must have exactly one.
I used the bar-end EW-RS910 Junction A in the end of my extension. That took some Dremel work on both the module and the inside of my extension to get it to fit. I got a good friction fit, so it requires no other tape to secure, and neither will it come out on its own. I also drilled a couple wire exit holes on my extensions near the back end of spacers so that I have a totally hidden wire path. The net result is that I have only one Di2 wire visible on the cockpit going from the stem into the frame.
Following are some summary bullets along with pictures of the Shimano topology I used along with a diagram of my specific design.
- The total package is complicated. It is 19 parts on the bike, each of which must be individually selected (except for the shifters, which you buy in pairs).
- I chose Ultegra RD & FD, because DA commanded a $350 price premium for just 66g in weight savings. I could find no other written benefit or advantage of DA.
- I chose Dura Ace brake shifters because there were very close in price, and because they say “Dura Ace,” which I do like.
- Even choosing the correct battery charger is confusing, due to different types of batteries and generations.
- I also used the method of measuring the wire lengths and then adding 10%. This gives you too much wire for the long runs and not enough for the short runs. Instead, I would probably modify that to add 20% for runs under 400mm and 10% above 400mm.
- You can put buttons nearly anywhere you want and individually program their functions. I may add another button on my extensions to change Garmin screens.
- I chose the single-button shifters for both my extensions and brakes. This commits me to Synchro-only. I think I prefer that, because it is a lean installation. But, you could mount a mix or two-buttons both places and use the convenient Junction A to easily shift between modes.
- Be alert to correctly attach the RD to the frame with Shimano’s new direct mount adapter. That adapter piece is supposed to be horizontal and there is a tab that should nestle into the B-screw stop on the RD hanger.
- Routing cables can range from easy to PITA, depending on your frame. It is very easy on an IA16. I pushed the RD cable in from the RD end, and it came out at my fingertips at the BB. And, I just dropped the other cable in at the calpac area and it showed up at the BB area with everything else.
- Routing cables through the Alpha X was pretty easy as well. I recommend removing the brake cable housings first to make more space for the Di2 cables. Then, reinstall the brake cable housings after you have the Di2 cables in.
- I choose the EW-JC130-SM splitter for my brake cables, because that let me use a 4-port Junction B instead of the 6-port Junction B.
- Don’t forget to get all of the frame grommets you will need.
- My Profile Design T1+ Carbon extensions had a ridge where the tube got thicker about 15mm in. This interfered with the EW-RS910, so I had to Dremel that smooth a few more mm in to allow room for the length of the EW-RS910.
- The FD has a little plastic cover that routes the cable behind it to keep it from hitting the wheel. (This is not shown in my FD pictures.) Don’t forget this little piece.
My parts list:
- Rear Derailleur RD-R8050
- Front Derailleur FD-R8050
- Brake Shifters ST-R8060
- Bar Shifters SW-R9160
- Bar-end Junction A EW-RS910
- Junction B 4-port 2x SM-JC41
- Wireless Unit EW-WU111
- Battery BT-DN110
- Battery Charger SM-BCR2
- Cable Brakes-B1 EW-JC130-SM
- Cable Extension-A 400mm
- Cable Extension-B1 500mm
- Cable A-B1 200mm
- Cable B1-WU101 150mm
- Cable WU101-B2 800mm
- Cable B2-Battery 250mm
- Cable B2-FD 300mm
- Cable B2-RD 650mm
The forum only allows a few pictures per post, so I will follow with a few more posts with additional pictures. These are Shimano's topology that I used as reference, my specific design, and all the stuff I had to buy. Last is the finished cockpit with just the single cable going from the cockpit to frame.