Did you know most Di2 hardware is cross-series compatible? You can actually mix different series and even different generations of Di2 hardware, as long as you make sure you follow the Di2 compatibility chart!
Hidden somewhere on the Shimano e-Tube Project website is a Di2/e-Tube compatibility chart. This useful PDF helps you select your components, making sure they're compatible before spending $$$ and installing them on your bike.
Want to use the mountainbike Di2 display on your road bike? You can!
Feel like upgrading your derailleurs but not your shifters? Sure! You can!
Compatibility chart? Where? How does it work?
The latest version of the compatibility chart can be found on the Shimano e-Tube project website under help/guides. At the time of writing the latest version of the chart is 3.4.2, we have mirrored it for you so that you can download it right here, should the Shimano e-Tube site ever go offline.
We have selected the SM-EW90 Junction box, R9150-series Dura-Ace shifters and two 11-speed derailleurs; the RD-6870 Ultegra rear derailleur and the Ultegra FD-R8050 front derailleur. Note that we could also have selected the Dura-Ace FD-9150 front derailleur if we wanted to.
The only thing you can never do is mix different speed derailleurs. All derailleurs have to support either 10-speed or 11-speed.
Mixing mountain bike and road?
So.. can you use mountain bike di2 hardware with road hardware? Sort of… it’s complicated. You should be able to use road shifters on a mountain bike – but would you really want to? However, let’s say you wanted to build a 1×11 Di2 setup? You’d probably want to take advantage of the Clutch System Shimano equipped the mountain bike rear derailleurs with, but use your road shifters. You should be able to do this no problem!
The only real limitation is that derailleurs you use have to be either road or mountain bike derailleurs – you cannot mix these derailleurs. Other than that you’re free to do whatever you want.
Like you’ve read above, we’ve mirrored the Shimano Di2 compatibility charts. Click either of the images below to downloads the full compatibility chart PDF. Note that the pages relevant to your set up depend on which series hardware and, perhaps more importantly, which battery you’re using.