Spoiler alert: this review will inevitably skirt around the obvious battle between the group at hand (Shimano's Di2 9150), and SRAM's top-shelf 12-speed AXS group. Both are absolutely fantastic, and we may later write a separate article pinning them head-to-head more directly. This review will focus more specifically on the Shimano group. But at least one important element is worth noting: in the category of electronic drivetrains, they represent nearly polar opposites in design philosophy. Where Shimano minimized batteries and added wires, SRAM instead minimized wires and added batteries. SRAM embraced 1x completely, where Shimano made a system that almost makes 1x obsolete. Both systems are absolutely brilliant, while being quite different.
Anyway, for this article, we'll mostly look at Shimano on its own merits, starting with an introduction of the system itself.
I've loved Shimano's electronic Di2 group since 2011 when we first reviewed Di2 7900. Shimano exploded out of the gate with the first viable electronic groupset. Undoubtedly, Shimano was the first to achieve this feat. Others may balk, and mention the earlier Mavic groups. But those niche rear-derailleur-only offerings (Zap and Mektronic) were neither complete nor fully-baked as complete systems. They were road-only, rear-derailleur-only, inefficient (they literally drew power from your pedaling to power the RD), and ultimately a flop.
The award for the first electronic drivetrain clearly goes to Shimano. And in the many years since Di2 premiered, Shimano did not rest on the laurels of that achievement. On the contrary, Di2 has grown into an entire ecosystem, and expanded wildly capability, popularity, usage, and just as importantly, competition. Shimano's electric revolution is here to stay.
Looking back on our first in-depth review, the conclusion was not only that di2 was a worthy entry into the high-end component market, but that it was redefining that market. Beyond that, we concluded that di2 had even more to offer the triathlete than it had to offer the road rider, who was its original target market. Fast-forward to today, and those statements remain true and poignant. That is, Shimano continues to introduce significant innovations with each cycle, but it is the triathlon/TT rider who continues to benefit the most.
The newest group, designated Dura-Ace Di2 9150, is easily the best in Shimano's history, and not only does Shimano continue to make significant advancements, but is constantly aware of the trends in the industry, and how to best equip athletes to address them. In my opinion, 9150 is the best group Shimano has ever made. Compared to SRAM's newest AXS groups, Di2 9150 is in a very tight race for the title of best group ever. Hit the jump; let's go!