We’ve seen and talked about Shimano’s Synchro Shift for both the new R9100 series Dura-Ace and M9000 XTR, where you can essentially program Di2 front & rear derailleur pairs to move in a synchronized manner in response to a single set of shift button inputs instead of separate shifters for each derailleur. While it certainly isn’t for everybody, there are some good rationales to automating the point where the front derailleur shifts to match the position of the chain on the cassette, with any time trial setup coming to mind. Well Shimano realized that they could bring that same functionality to their previous E-Tube based Di2 road groups if riders simply updated to the latest battery that packs the additional processing power required for the automated shifts. So now if you have an Ultegra 6800 or Dura-Ace 9000 Di2 setup, you can get Synchro Shifting by upgrading to the latest internal battery, and updating your groups firmware through the E-Tube app…
The latest Di2 battery that you need is the BT-DN110, which has more memory that the previous generation and can handle the additional processing load & storage needed to manage the multiple shift patterns of Synchro Shift. To get the new functionality allowing Shimano to decide when to match front & rear shifts, users with the new battery and compatible front (FD-6870/FD-9070/FD-9150) & rear (RD-6870/RD-9070/RD-9150) derailleurs just need to upload the latest E-Tube firmware to their battery. You can do that either through the wired connection to your PC or through a Bluetooth connection to the E-Tube App if you already have a wireless controller installed.
Once updated, you can cycle through modes much like you do on the new Dura-Ace with the bar-end button, but with the regular control button on the external junction box under the stem on most Di2 bikes. A new sequence of flashing lights tells you what mode you are in, as you double click to cycle through modes – solid red light indicates manual shift, twice blinking red indicates the 1st Synchro mode, & thrice blinking red indicates a 2nd Synchro mode.
That would usually mean – Manual, Full Synchro & Semi-Synchro – although you can customize each mode in the E-Tube app as well if you prefer more adjustability of when and how shift synchronization occurs. For a quick refresher, Full Synchro shift allows the rider to only think about shifting up or down and automates the shifting of the front derailleur to stay in an optimal chainring:cassette gearing combination. Semi-Synchro shift makes corrective rear shifts to match your front shifts so you get maintain a smoother transition when you shift the front derailleur and can keep a more consistent cadence.
In either Synchronized Shift mode the rider still maintains control over both derailleurs, and can use the regular buttons to control or correct shifts as needed (assuming you don’t remap shift function away through the App.) Synchro Shift was designed to complement regular Di2 function, and is intended to improve usability when paired with auxiliary sprint, climbing, and time trial shifters.
