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.