The videos are now posted!! I put them at the top so they would be easy to find. Later, I will place them in the article where they are relevant.
So, while a few other projects are on hold and I try to dig out of all the bikes in the busy season that we’ve been repairing and building, I found some time today on my day off to stop by the shop and experiment with some different combinations of road and mountain electronic shifting components and how each system reacted for some new build scenarios. My thoughts in particular go toward touring setups and long endurance racing. While this won’t be the complete combinations of every single component, I covered quite a few of them and think it will be a great reference for everyone if they are trying to mod some Di2 builds or come up with better gearing solutions for specific rider needs. That being said, it was really just a fun time to see what will work with each other and how it is going to shape future electronic systems.
All of the experimenting except for actuation of the XTR Di2 front derailleur were done off the bike so I could quickly switch components and visualize the connections for the varied setups. My first nagging question was how well the XTR Di2 rear derailleur worked with Dura-Ace Di2 shifters. I took a couple of videos of the components working (or not working) so you can see the component selection all in one frame and how the parts respond. I’m also thinking of making a compatibility chart for the various components so it can be utilized by someone who hasn’t been able to test it themselves. Onto the fun part!
I connected the XTR Di2 rear derailleur to a Junction B port and connected that to an internal seatpost battery and front Junction A. From Junction A, I connected the rear shifter and saw a nice 75% battery level. Then, I pressed the shifter button and eureka! It worked just fine. The more machine-like sounding motor quickly actuated for both single shifts as well as a continuous up or down shift when either shifter button was pressed and held. In essence, it worked just like a Dura-Ace Di2 rear derailleur would, only now it is possible to have a gearing range in the back of up to 42 teeth, which allows for an exceptional mountain climbing road bike. Check out the photos below.
I had expected that this would be the result. It makes sense considering that the etubes are used on both systems and the software is very similar. From this point, I was unsure of the full connectivity and wanted to try the next scenario. I determined that the next obvious choice is trying to use the mountain display (Junction A on MTN Di2) with a Dura-Ace Di2 rear derailleur and Dura-Ace Di2 levers. This display would be particularly helpful for long trips to see what gear the chain is in and the battery level. Seeing this visually could very well make much more sense to some riders. I find it fairly easy and naturally to look down at the bike while riding and check my gear, but others coming through the shop have difficulty with this in some cases and the addition of the display is helpful solution. Also, while the mountain junction A has only three ports (one for the Junction B wire connection and one each to the shifters), I found a great solution of even more options which I will get into later in this article.
After disconnecting the road Junction A from my bench setup, I connected the Dura-Ace rear derailleur to the Junction B connection and connected the XTR mountain junction B to the Dura-Ace Di2 shift levers. Happily, the display lit right up and I was able to shift through the rear gears just like with using the road Junction A, except the rear cog number was displayed on the XTR display as well as the battery level. It should be noted that when I connected the XTR rear derailleur to the road junction A and the Dura-Ace Di2 rear derailleur to the XTR mountain Junction A, both would not work in Synchro mode while using road levers. I did expect this as well because the road components were not designed with Synchro shifting in mind and is likely specifically programmed into the XTR Di2 shifters. Check out the photos.
So, as a summary at this point, we have learned the following: Both the XTR Di2 and Dura-Ace Di2 rear derailleurs work correctly (except for Synchro Shift with Road Lever and Mountain RD) with either mountain shifters or road shifters as well as both work with either road or mountain Junction A. I swapped the shifters out at this point and connected an XTR Di2 shifter to the Dura-Ace Di2 rear derailleur and mountain Junction A setup, which also worked correctly. It was able to actuate multiple gear shifts, single gear shifts, and continuous shifting when either button was held down. Check it out below.
So, the rear derailleurs seem to be relatively interchangeable, which is a great thing. It will allow further possibilities of different builds. In my mind, I envision urban commuter flat-bar bike with XTR front shifting, Ultegra Di2 rear shifting on an 11-32 cassette, and a nice mountain Junction A display. Also, I envision this as a 1×11 setup, which I will explain why next.
It’s great that the rear shifting was so easily compatible, but I thought, what about the front? I took the original setup to start (Dura-Ace Di2 levers with road Junction A and XTR Di2 rear derailleur) and connected an Ultegra front derailleur to the system. Click, click, click. No luck. I swapped the Junction A for the mountain Junction A with no change. The front derailleur would not work while the XTR Di2 RD was connected. So, just to check, I grabbed the Black Inc Cannondale that I featured in my last article with an XTR Di2 front derailleur on it and placed it in my bike stand. I disconnected the Ultegra Di2 front derailleur and connected the XTR Di2 front derailleur. Yay! It worked great with the Dura-Ace road levers (except for no Synchro shifting).
This might simply be the difference in software for the components and might change in the near future. I will be writing a second part for this article soon when I have a chance to connect the mod’d systems to the software and see what is recognized or if firmware is simply the issue. Questions I still have now include: If I connect mountain components to a road setup, is it possible to upload road firmware to them and have the system work interchangeably? Also, if I do the opposite and connect an Ultegra Di2 front derailleur to a full mountain system and check the firmware, will i be able to make it compatible then? I am not sure of these and few other small issues, but it was really nice to get ahead of the curve and start customizing these electronic setups as much as we can.
My last experiment was to connect a sprinter switch to the Dura-Ace lever to see if the XTR Di2 rear derailleur would work. I guessed that it would and it certainly did. I was able to actuate shifts just like the switch would do on a road bike setup. This has a lot of promise as a satellite shifter of sorts for long ascents where multiple hand positions are needed. I can even envision taking the guts out of the Dura-Ace lever for the shifting connection for the sprinter switch and just having the switches as hidden shifters for a sleek (and much more lightweight) look on a flat bar XTR Di2 setup. The possibilities are there. We just have to test them and be a little creative. I hope you enjoyed the photos, the video, and the experimentation. There will be lots more to come.
– SNC
secondnaturecycling 
Hi there, would xtr di2 shifters work on dura ace di2 fd and rd setup?
Hey what a great post! Thanks for the info. I have a few questions about a new XC bike I’m building. Okay so here is my optimal setup.
One xtr shifter, duraace rear derailleur with 11-30 cassette, and xtr front derailleur (for 26/38 crank). Is this feasible with one shifter? Do I need the mountain junction display in order to have syncro shift? I’d just as soon stick a d-fly in there and have gears displayed on my Edge 1000 in order to save weight and clean up the bars by running a road junction. I have a feeling though the mountain junction is responsible for syncro shift though?
Oh yeah one last question, will a dual shift on the xtr shifter actuate a dual shift on the duraace rear derailleur?
You should be able to run a road junction with the mountain shifter, but the rear derailleur prevents the synchro shift from happening. The Dura-Ace isn’t programmed to accept synchro shifts. In the long term, this is a scenario (if you want one shifter) where you stick with the XTR front and rear.
Okay that makes sense. Probably I’ll end up running both shifters then and a road junction. The d-fly makes syncro shift less useful.
Did you test to see if a double shift on the xtr rear shifter actually shifts the duraace rear mech twice?
I hope you are still tending to this thread. I have dome much of what you have. The problem I am running into is, the FD-M9070 (2x)only takes up 10 teeth, which stinks if your want to run a 50/34 front (Note – I am trying to set up a tandem for I need high highs and low lows). What I really need is a true hack that will allow a FD-9070 or FD6870 to run with the XTR RD-M9050. I am thinking about trying an FD-M9050 (3X) which takes up 18 teethh and set the limit screws and double shift quickly toi get to and from 50 to 34… Note that the cage on the XTR M units is very small and trying to run a 50/34 will not work. I have considered physically modifying the case, but will am looking for advice before heading that direction.
Actually, that sounds like a great option to try with the triple front derailleur in order to get the right spacing for the chainrings. I would definitely see if your shop has one to try before you buy it. Also, I have considered modifying the cage before, but this will likely cause some other issue to occur or may indeed ruin the derailleur, which would be costly. You are correct that the front Dura-Ace derailleur will not work in conjunction with the rear XTR derailleur. I am putting together an article on the new SRAM eTap that we got to build this past week and changing the cage to a long cage may solve many more problems overall. From the fact that the components are ‘synced’ and use signals from the shifter to the derailleur (which has the brains), I see hacking this as an easier solution but modifying the rear cage. Plus, I expect to start seeing multiple models of the erar derailleur (i.e. short/med/long cage).
Where are you located?
Arlington, VA
Bummer – you like to get a few folk together with similar needs to troubleshoot this. A software solution is the BEST – get XTR and Dura-Ace to work together.
Yea, my next step is to try and connect the components and run the software in road mode and see if it will reprogram the rear derailleur (XTR) to work with the front (Dura-Ace).
I was wondering if you could try a Alfine SW-S705 shifter with the XTR Di2 Rear Derailleur and display. To see if the shifter would work directly with the XTR display and derailleur. I have seen people use Cateye button switches spliced into the E-tube wires at least that is what it looks like. I’m waiting for other parts before I start cutting up my own e-tube wires and sprinter shifters to make smaller shifters for my mtb.
Bill, that’s an interesting question. I don’t have an Alfine available at my shop, but I will definitely ask my Shimano tech rep about it. That would be sweet for an urban or touring setup. Thanks for the question. I’ll dig into it and let you know.
Click to access HM-CC.2.10.0-00-EN.pdf
Awesome link. Thanks! Always more fun to experiment hands on though than read a list… but super good reference chart
DI2 Shimano Alfine is compatible with the xtr DI2. I have it installed on a grade gt
Josep, that’s awesome to know. Thanks for the feedback. That would be a sweet setup.
Thanks for taking the time and trouble to put together a true work of art. Perhaps it’s just me being a bit slow, but could you let me know where you might actually connect the XTR Dislay to a working Ultegra di2 setup. I have got a 5 port junction A which is full, on account that I’ve got sprinter switches, TT switches and the climbing switch. I think I have got 1 spare port on the left hand Sti lever, might this be OK or will I have to compromise and remove 1 of the TT switches out of junction A?
Jamie, thanks for the comment. Yes, the only way you would be able to use the XTR display with your TT setup would be to only have one set of shifter buttons (so either no shifter buttons on the basebar brake levers or no shifters on the aero extensions). I am not sure, but you possibly could just run one working shifter on your extensions (for the rear derailleur) and one working shifter on your base bar brake levers (for the front derailleur). I would leave the other shifters on, but not plugged in. Generally, you are always in the big ring when in the extensions, so you would only need rear derailleur shifting and vice versa when you are holding the basebar (climbing in small ring and not shifting rear often).
Great to see someone take the time to demonstrate various components. However there seems to be a couple gaps in all the info posted so far.
1) “when I connected the XTR rear derailleur to the road junction A and the Dura-Ace Di2 rear derailleur to the XTR mountain Junction A, both would not work in Synchro mode while using road levers.”
Subtle point here is that even the XTR derailleurs will not do synchro when not connected to the XTR display, regardless of what shifters you use. Plus, all shifters are only buttons, and do not contain any program logic. Obviously having the XTR display + derailleurs are the deciding factor.
Did you test XTR derailleurs + display + DA road shifters and get synchro to work?
2) For the question regarding the need for more front ports, you can add as many Junction B 4-port boxes to the system as you like (they are transparent to the components and logic). So if quick connect/disconnect of TT bars is desired along with the XTR display, one can add a Junction B box at the front and use a short interconnect wire from the display to join it into the system. This will provide 5 usable ports at the stem location.
3) Although Di2 firmware updates cannot be rolled back to earlier versions, it is somewhat irrelevant to post results of old firmware combos. Likewise, posting results without stating the firmware versions used at that time.
Thanks again for uploading your results. Hopefully we will see more in the future.
Thanks for the refinement. From my combinations and experience, any time the road components or junctions are introduced to the XTR, the synchro will not work. Definitely a great idea posting the firmware versions of each component after testing. When I start at the new shop I am going to, I will make it a point to test these combos further and include firmware versions. There probably are some older firmware versions that will not work at all when combined. The reference chart that RADO posted above is a great tool for initial questioning. Since 9100 Dura-Ace is out now, I would like to test them with the XTR–particularly with the rear mech starting to borrow features like the Shadow Plus mount design and the resemblance of the derailleur bodies in the XTR and 9100 rear derailleurs.