Shimano XTR Di2 electronic shifting (continued from Part 1) There are six specific Di2 components: The rear derailleur, the front derailleur, front and rear shifters, a battery, and a display unit/junction box (or junction box only if you choose). The cranks, chain, and cassette are all common to mechanical XTR. Di2 is available in single, double, and triple ring crankset options.
How it works?
The simplified explanation (and perhaps slightly obvious one) is that the rider initiates a gear change at the shifter. This sends a signal to the display unit/junction box (the brain), which in turn sends a signal to either the front or rear derailleur (or in some cases both - more on this later), which activates a small electronic motor in either the front or rear derailleur, that then changes gear. All this is powered by the battery. The battery can be located either in a purpose designed seatpost, or the steerer tube of the fork (with a specific stem), attached to the frame, or in some cases in the frame itself.
The key advantages of Di2
Firstly, Di2 is, in theory, a “set and forget” system. Without any cables to stretch, or to get contaminated with moisture and grit, once Di2 is set up for your bike “it should never need adjusting”, and you should get crisp, clean gear changes every time. Shimano are so confident of this repeatability that they suggest if you do start having shifting issues it is likely to be due to an issue with another component of your bike; for example a bent derailleur hanger or a damaged frame.
Secondly, because rider input at the shifter is no longer mechanically connected to the subsequent action at the derailleur, but rather by wire and with the advantage of an electrical motor in the mix, the interaction at the shifter can be tuned to provide the best experience for the rider, while the action at the derailleur can be tuned to provide the best possible shifting. This advantage is probably best illustrated in the shifting of the front derailleur. While the feel at the lever is not too dissimilar to that of a mechanical shifter, the derailleur is actually shifting with more force. In theory this makes for a faster gear change and means that you can shift gears while you’re applying more load to the pedals.
The third advantage (and perhaps the most interesting) is customisation, and most notably the ‘Syncro’ option. Because the Di2 system is managed electronically and has some on-board smarts, the way it works can be tweaked to an individual’s preferences (for example swapping which lever shifts which derailleur), and it can also be set up to help manage the way the rider shifts through the gears, ensuring the most efficient, and mechanically sound, gear selections. The Syncro option allows the rider to use just one shifter to click up and down through the entire gear range (front and rear). I believe this option alone should make naysayers pause for thought. All of sudden you’ve got the simplicity of a single shifter with the extended gear range afforded by multiple chainrings. All the rider has to do is decide whether they want an easier or harder gear, push the appropriate lever, and the Di2 system takes care of the rest.
The final key advantage with Di2 is, I believe, its potential for expansion. Already there is the option to integrate Di2 with the Fox iCTD system. This enables you to control the mode setting (climb, trail, descend) of both the fork and shock at the handlebars, and at the push of a button. There is certainly scope for the system to be further expanded going forward. Although there was no mention of it, I see no reason why you couldn't have an electronically actuated dropper post. And while the idea of having your bike wired from head to toe might initially seem a little off-putting, in reality Di2 enables a much cleaner looking bike setup (especially in frames that are designed to house the battery and a secondary junction box).
My time riding Di2 in Australia was limited, but it was enough to garner some first impressions. We hope to put in more time on the groupset soon, after which we'll be able to give a proper review. In the meantime here are my initial thoughts:
The very first thing I noticed was that the paddles on the shifters were set up in reverse to what I had expected. When I climbed aboard, my first action was to shift into an easier gear and instinctively I depressed the larger of the two paddles on the right hand shifter, which actually shifted into a harder gear. This felt counter-intuitive. It was suggested that this was one of the things that could be easily changed in setting the preferences. However it's something I expect you'd soon become accustomed to. Otherwise the action of the shifters felt positive and not unlike the mechanical levers. I'm told that the road Di2 has a far more subtle feel at the shifter, but it was decided that for mountain biking it was important the action was more purposeful, positive, and familiar. Which it is. The shifting felt crisp, clean, and consistent. Every shift was accompanied by a distinctive, and distinctively electrical, whirring from the derailleur. Although the whirring seemed a little a slow, in reality the gear shift was very quick and matter of fact. As claimed, the shifting seemed to work better under pedalling load than mechanical systems. One of the things I appreciated most with the system was that every gear change whether up or down, front or back, had the same consistent feel at the shifter.
Switching to Syncro mode via the handlebar mounted display was simple, and after a short spin I was struggling to fathom why you'd ever choose anything other than this mode. Being able to run though the entire range of gears from one shifter was brilliant (like the experience of running a single chainring, but better). In the short riding time I had, I was fairly confident that I would choose to ditch the left hand shifter and use Syncro mode full time, freeing up space in the cockpit for a dropper post lever and further simplifying the bike setup.
On that note, my final impression from my ride was just how pleasant it was to have a super clean cockpit. Because you now have a system that replaces mechanical shifter cables with the far more compliant electrical wires, the options for internally routing are greatly improved. The Di2 bike that I rode was more or less internally routed all the way from the shifter through the bar, stem, and frame to the derailleur. I'm used to seeing at least four or five separate cables and hydraulic hoses in my field of vision when riding; to have only two hydraulic hoses was an unanticipated joy.
So there you go, my first impressions of Di2. Hardly a comprehensive review, but stay tuned as we hope to be able to bring a full review sometime soon.
Also coming to a future issue of Spoke magazine is a full review of the new XTR carbon Trail wheelset . . . .