Review: Shimano Dura-Ace Di2 9150
Aug 31, 2020
article & images by Nick Salazar
Synchro shifting is something we've wanted for a long time, and we're THRILLED to see Shimano finally do it in such style. We first saw a user-made version of this concept back in 2010, from Fairwheel bikes. They hacked their Di2 system, using custom circuitry and wiring, to tell the system when to shift the front derailleur and rear derailleur, asking the rider to input only "up" or "down" on the shifter. This was a revelation back in 2010, and something we begged and pleaded Shimano to develop as a standard option. Ten years later, IT IS HERE. And yes, it is absolutely and completely AWESOME.
Shimano calls it "Synchro" shifting rather than "Sequential" shifting, but it is identical to the concept Fairwheel developed those ten years ago. But predictably, Shimano has improved upon the concept, and made it a natural and native option in the system. Want to control the derailleurs independently? You can do that, if you're weary of the change, or use this new Synchro shifting, which is undoubtedly better. There are two different modes: S1 for "Semi-Synchro Shifting," or S2 for "Full Synchro Shifting." Forget about S1 and just stick with S2. It's awesome.
With Shimano's software, dubbed "E-Tube Project," available for PC, iOS, and Android (currently no Mac version), you can completely customize your bike's shift settings. It will allow you to input your bike's chainset teeth, cassette range, and completely customize the shift points, both up and down. It's just perfect, and exactly what you want. If you are a geek and care about the exact shift points, it's just what the doctor ordered. But if you're not a tech-head, no worries. The default settings are VERY GOOD, and will do just about exactly what you'd want, as long as you are in the Full-Synchro (S2) shifting mode. In my experience with the bike, I didn't end up changing any of these settings. I just got on the bike and rode. I end up with more usable gears than with AXS, closer gear ratios, and I still don't have to ever look down to worry about which chainring I'm in. The system is completely set-and-forget. It 100% replicates the benefit of 1x I've always been drawn toward, which is the simplicity of a simple "up" or "down" shifting choice.
The one thing it doesn't offer compared to a true 1x system is the absence of a front derailleur, meaning a potential aero loss. However, independent tests on this have had mixed results; some folks have concluded that the front derailleur doesn't incur an aero penalty with a pedaling rider on board.
In all, I really loved Synchro Shifting. A lot more than I thought I would. It truly behaves like a 1x system, with none of the potential drawbacks of 1x (wider gear ratios, poor chainline, drivetrain friction losses, lack of a chain catcher). Let's hit the jump one last time, and talk conclusions.