Gear Shed

First Look: Shimano XTR Di2

With a new smart drivetrain concept, the Japanese component manufacturer unveils electronic shifting for mountain bikes.

Shimano's new electronic shifting technology for mountain bikes could be revolutionary.     Photo: Courtesy of Shimano

Though Shimano’s announcement at Sea Otter of a new 1x11 XTR component group had us excited, it was the whispers of a new electronic mountain group that sounded truly groundbreaking. Having kept the group set under wraps for the last two months to finalize development, the company announced XTR M9050 Di2 last Friday.

The new components blend all the user control of the new XTR M9000 group, including 1x, 2x, and 3x11 options and compatibility between all three, with the technology of the second generation of road Di2

That means M9050 utilizes the same plug-and-play E-tube wiring, which lets riders easily add and subtract components from the system. And it also permits user-driven programming by way of a personal computer to customize shift speed, preferences such as auto-shifting through the entire range with a single button push, and even which components control what functions (for example, front shifting could be controlled either right or left). 

But Shimano has also improved on its Di2 system. For one, the new Firebolt shifters aren’t constrained by the shape and form of earlier mechanical designs, but instead get a brand new look and shape based on ergonomics. If we had one criticism with Dura Ace Di2, it was that Shimano didn’t take the opportunity to rethink and overhaul the shifter placement and design for easier use, so it’s nice to see this function-driven metamorphosis.

Even more radical is the new Synchronized Shift system, which allows riders who use two- and three-ring setups up front to control both front and rear derailleur movement with a single shifter. The company has created a handy, in-depth video that delves into the mechanics, but the short of it is that if programmed to run off one shifter (which is entirely optional), the software picks the most efficient gear combinations and ratios and shifts both front and rear derailleurs accordingly. In the instance that both derailleurs need to move at once, the groupo first emits an audible tone to alert the rider before the shift. 

While Synchronized Shifting should produce the most efficient gear combinations (and is only possible because of Di2’s ability to shift under load), Shimano acknowledges that some users may want full manual control. So users can program that option themselves, including the use of two shifters, as well as easily switch between the settings at home. That means you could use both shifters and a manual setting on a course that you thought might have especially demanding or peculiar shifting needs, but then plug in and switch to Synchronized Shifting mode for a different ride the next day.

One other interesting development: Shimano has collaborated with Fox so that the new XTR Di2 system and battery work seamlessly with the electronic Fox iCD (Intelligent Climb Descend) suspension.

It’s a good move on Fox’s part given the ease and utility of Shimano’s E-Tube wiring, and we’re happy to see the standardization between the two. Then again, given Magura’s incredibly effective wireless system, the big question is when and if both Shimano and Fox will nix the wires completely.

Though M9050 Di2 has several additional components to the mechanical group set, including the battery and a head unit that displays gear ratios, battery power, and other pertinent info, the system should be comparable in weight to the standard equipment thanks to reduced weight of the tubing and a few lighter components.

Shimano says that a 2x M9050 Di2 setup controlled by one shifter will weigh exactly the same as an M9000 mechanical arrangement (with two shifters). Note, there are two battery options: the heavier of the two mounts to the bosses behind a standard bottle cage and acts as a data hub and charging port, while the lighter one hides in the seat post.

Perhaps the biggest question is whether an electronic system is durable enough for the mud, water, and rough surfaces of mountain use. Shimano insists that wires are actually more resilient and less susceptible to trail and weather conditions than are standard cables, and they say XTR Di2 is a fully waterproof system. They claim to have logged some 12,000 miles in development and insist they are confident the parts will hold up. We hope to take delivery of a group set later this summer and log some significant time on it to see whether or not that’s the case.

Prices aren’t set, but as with the road components, XTR M9050 Di2 is expected to carry a similar 40-percent premium over the mechanical option. The system will go on sale to the public late this year.

There’s no word yet on when, or if, the technology will trickle down to the XT level, but judging by the road Di2 components, that’s a distinct possibility—though it might take at least a year. We also anticipate that Synchronized Shifting could soon be integrated into Dura Ace and Ultegra Di2 systems.

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