Words by Flow | Images by Flowtographer

We’re shocked! Shimano have finally brought electronic shifting to the mountain bike market with 11-speed XTR Di2.

This electrifying development has been rumoured for years, but when Shimano announced a new mechanical 11-speed XTR groupset last month, we started to have our doubts; perhaps Di2 for mountain bikes wasn’t going to happen after all? But the electronic era is here, and frankly it looks amazing.

Shimano XTR Di2-8

The benefits of electronic shifting are many and are arguably more significant for the mountain bike world than on the road; zero cable maintenance, no shifting degradation in bad conditions, instant shifting response. But the potential for electronic shifting to free up frame design is also massive – without the constraints of keeping a clean, smooth line for a shifter cable, who knows where suspension design can go?

Flow was lucky enough to spend some time at Shimano Australia’s HQ recently, where we got the opportunity to actually test ride a near-production prototype version of the Di2 groupset.

The Di2 XTR groupset shares many of the same attributes with the mechanical version (gear ratios, crankset options etc), so we’ll stick to the points of difference and the aspects of the Di2 system which really grabbed us.

Shifters:

Just what the Di2 shifters would look like and how they would operate was a real unknown. Speaking to Shimano representatives, we learnt that there were many iterations, before ultimately settling on a paddle design that’s not too dissimilar to existing XTR shifters. The shifters still feel and sound like a mountain bike shifter – there’s a snappy, loud click with every shift, and there are separate paddles for up and down shifting.

Shimano XTR Di2-3

Maintaining the feel of a traditional shifter (albeit without any cable friction) was a very smart move. If there’s one criticism that Di2 shifting encounters in the road world, it’s that the shifting action feels too disengaged, more like clicking a mouse than shifting a gear.  XTR Di2 manages to keep that engaging, positive feel of a ‘real’ shifter.

The operation of the shifters can be customised too, via Shimano’s E-Tube tuning system. The up/down-shift function of each paddle can be swapped to suit your preferences, and the number of shifts executed when the shift lever is held down can be set. For instance,  you can determine if you want to shift a maximum of two, three or four shifts in one go, or if you’d like to keep shifting for as long as you’ve got the shifter depressed. You can also control the speed of the shifts.

Synchro Shift:

Now this is pretty cool. Part of the appeal of a 1×11 drivetrain is the absence of a left hand shifter and the clean simplicity this brings. The downside, of course, is the slight reduction in gear range associated with having fewer chain rings. But XTR Di2′s Synchro Shift option allows you to run multiple chain rings ( 2x or 3x ), and with only one shifter. It’s pretty crazy.

Shimano XTR Di2-2

As you shift through the 11 gears of the cassette, Syncro Shift automatically shifts between chain rings to ensure the jumps between gear ratios are smooth and even. The video above is perhaps the easiest way to grasp the system. It shows Synchro Shift in operation for a triple chain ring setup. On the right you can see which gear of the cassette is currently selected, on the left is the chain ring currently in use (Top, Middle or Low). As you can see, it covers the whole gear range, from the very highest to the very lowest gear, in 14 consecutive shifts. NB. We weren’t able to show you the actual derailleurs in operation as they were deemed to be ‘too prototype’ for video.

By way of example, imagine you’re riding in the big chain ring. As you start to shift to lower gears, the Synchro Shift system will automatically drop the chain to the next smallest chain ring, and will simultaneously shift up a gear or two on the cassette to ensure the jump between gears is even.

Shimano XTR Di2-7

Once again, the parameters of the Syncro Shift system are all totally customisable. For example, you might want to program the system to use the big chain ring primarily; in this case, you could set the Synchro Shift to only drop to the smaller chain ring once you reached the lowest gear of the cassette. You could also set it to then jump back up to the big ring once you’d up-shifted to the fourth gear of the cassette. Because you can determine the parameters of when a front shift is executed, you’re not going to be sprung with a ‘surprise’ jump between chain rings. To be doubly sure, the system actually gives you a double beep to let you know when it’s about to shift between chain rings.

Shimano XTR Di2-4

Of course if you’d prefer the more traditional approach of separate shifters for front and rear derailleurs, then you’re not out in the cold – XTR Di2 systems will still be sold with both left and right-hand shifters and the system can be set to Manual mode, rather than Synchro Shifting.

Shimano XTR Di2-1

Battery:

Like Shimano’s Di2 road groupset, the XTR Di2 system uses one central battery for the whole system, rather than individual batteries for each derailleur. The cylindrical battery can be bolted to bottle mounts, or it can be run internally if your seat post allows. There’s also scope for mounting it inside the fork’s steerer tube, as we’ve seen some riders (such as Dan McConnell) already do with FOX’s electronic iCD lockout battery. In the pipeline is a range of specially designed bars and stems with ports for Di2 wiring.

As with Di2 road shifting, we’re sure it will only be a matter of time till the batteries are internalised and frames are optimised for wiring, rather than shift cables.

Display:

The simple display sits neatly alongside the stem, where it won’t interfere with other devices like your GPS or lights. Aside from displaying which gear/chain ring you’re currently in, you’ve also got information about battery life, the mode currently selected (Manual or Synchro Shift), as well as suspension settings (see below). The display also serves as the adjuster for fine tuning the shifting, just like a barrel adjuster does on a mechanical shifter.

Shimano XTR Di2-5

FOX suspension integration:

The partnership between FOX and Shimano continues to strengthen with XTR Di2, with FOX’s iCD electronic lockout integrating with the XTR display. On the far right of the screen you’ll find an indicator letting you know if your shock and/or fork is in a Climb or Descend setting.

Wheels:

While at Shimano HQ, we managed to get our hands on some all new XTR wheels too. With carbon laminated rims and a very pretty hub finish, these are the best looking XTR hoops yet. Rather than using a dedicated UST rim (without any spoke holes), the new XTR wheels go for the far lighter option of a tubeless tape, as has become the standard of late.

Shimano XTR Di2-11