Shimano has officially released the mountain bike industry’s best-known secret. Di2 electronic shifting for XTR has been anticipated since the Di2 first appeared on the company’s Dura Ace road groupset five years ago. 

Widespread acceptance of Dura-Ace Di2 is Shimano’s assurance that its new 11-speed XTR M9050 Di2 drivetrain will overcome the inevitable resistance it will receive from mountain bikers. Di2’s electronics are now well understood by retailers and mechanics.

In short, Shimano’s timing could not have been better for the off-road scene.

Shimano’s XTR Di2 system drives the front and rear derailleurs with powerful digital-proportional servo motors, not that much different from how the Dura Ace Di2 works if you’re familiar with it. The servo mechanisms are built into the derailleurs and each contains its own micro-processor, so if one part fails, the others can continue to function.

A single “E-Tube” wire that conducts power from a centralized rechargeable battery and communicates signals from the Firebolt shift buttons connects the sealed and waterproof electronic components. A small, handlebar-mounted display indicates battery life gear selection and your choice of shifting mode.

Shimano’s XTR Di2 system is intended to serve mountain bikers in all conditions, and its near-instant shifts require powerful motors, which draw heavily upon the battery, so the Di2 is designed to hibernate between actions. When a shift is called for, Di2 turns on, remembers which cog and chainring the transmission was in, shifts to the next gear and then shuts down. Hibernation greatly extends Di2’s battery life. Most owners on the Dura Ace Di2 enjoy months of riding between charges. More importantly, you never have to turn the system off. Just pull the bike off its peg and ride, the same way you’d treat a bike with a cable-operated derailleur system.

Would you be getting the XTR Di2?