Shimano began using batteries to power some of their high-end drivetrains over seven years ago when they first introduced Dura-Ace Di2 for the road. That was eventually followed up with an electronic drivetrain for us dirty mountain bikers, XTR Di2, in 2014. The latter cost around $2,800 USD for a complete 2x11 group, which is enough coin to buy a decent entry-level bike, one that even comes with a drivetrain, albeit controlled by silly steel cables. XT Di2 costs roughly half as much depending on how you configure it, with a 1x11 setup coming in at around $1,300 USD. Yeah, that's still a load of money—I could live in Central America on $1,300 for a long time—but it's at least a bit more realistic for some riders to consider.
XT Di2 is, for all intents and purposes, the working man's electronic drivetrain. It should function to within a shift cable's width of its twice as costly XTR Di2 brother, and it sure as hell better offer some sort of advantage over the now "antiquated" traditional XT drivetrain.
So, does it? To find out, I spent far too long installing an XT Di2 1x11 drivetrain onto my bike in December, and Vernon Felton had the same thing but with two chainrings (argh, a front derailleur!) bolted to his own bike. Two testers, two different setups on two different bikes, and four solid months of use throughout the wettest, nastiest winter that we can remember.
It'd be easy to add another thousand (or ten thousand) words pouring over all the details of what makes XT Di2 tick, and while that's usually how I roll, I'll spare you the essay by sending you elsewhere on Pinkbike. You can read all the tech mumbo-jumbo in Mike Kazimer and Vernon Felton's 'First Ride' piece
from back in November of last year, or if you're really keen, you can get the lowdown on the history of Di2 in the dirt by reading RC's comprehensive early look at the first XTR Di2 group
back in 2015.
XT Di2 can be had in either a single or double-ring configuration, and just like the more expensive XTR version, shifting speed and style can be customized to the rider's preference. Shimano's app can be connected wirelessly, or via a USB cable to your computer, and it allows riders to tailor the shifting to their liking. You can speed up or slow down the shifting, switch the function of the shift levers, and even enable Synchro Shifting that sees one shifter control both the front and rear derailleur.
All neat stuff, but the question that really needs answering here is if there's actually an advantage to letting a computer and tiny motors do the work for you instead of ratchet wheels with cables controlled by your thumbs. I'm a lover of any interesting technology, even electronics, but the product needs to do something better, doesn't it? Let's find out if it does.
• Drivetrain: XT Di2 one-by
• Bike: Rocky Mountain Element 990 RSL BC Edition
• Duration: early December to mid-April
Are you prone to fits of rage? Or do you have the calmness of a sloth high on laughing grass? Those who fall into the former category may want to put on a soothing nature soundtrack with rain noises and birds making bird sounds before jumping into this job; it's not nearly the simple task that I was lead to believe. Sure, bolting the bits onto your bike and plugging the wires in isn't difficult—this is actually easier than installing a traditional drivetrain as there's no farting around with cable tension to get it just right—but it's the damn battery, junction box, and rat's nest of wires that nearly gave me a stroke.
You having a stroke or not might come down to whether your frame was designed to accept Di2, and it's not a homerun even if it is. To be fair, a lot of bikes will require you to remove the fork and slip your bubble-wrapped Di2 battery and junction box into the downtube, so that's what I did... only to have one of the wires pull out, forcing me to start over. I did eventually end up getting everything jammed in there only to have the battery rattle loose from its bubble wrap cocoon during the next ride and slide down towards the bottom bracket. And that's when one of my eyes started to twitch all on its own.
In the end, I swallowed my pride and strapped my lithium-ion foe to the side of the bottle cage. Ghetto, yes, but it took all of three minutes, and I avoided having a nervous breakdown, which is nice.
Battery battle aside, XT Di2 is simple to get running once you have everything installed and connected. There's zero cable tension adjustment because, well, there is no steel cable, and the brain in the control box figures everything out for you. I wish the rest of my life were like that.
• Drivetrain: XT Di2 two-by
• Bike: Pivot Switchblade
• Duration: early December to mid-April
Shimano kitted out my Switchblade test bike with the 2x version of XT. I opted to control both my front and rear derailleurs with a single (right-hand) shifter. Installing the front derailleur took all of two seconds. Wiring the whole system up, however, took longer. A lot longer. Shimano’s Joe Lawwill did all the hard work, I helpfully sat around and made jokes while he snaked miles of wire through the frame.
The installation should have been a breeze. Pivot Cycles’ notoriously Type-A founder, Chris Cocalis, sent over a wiring schematic. What’s more, his bike features a very tidy port for the battery, so we didn’t have to stuff the battery in a top tube or fork steerer or stoop to strapping it to the side of the downtube with duct tape and baling twine (What’s up, Levy?). The Di2 battery went in easy. Teasing all that limp wiring through the down tube and chainstay? That proved more of a pain in the ass—even for a seasoned wrench and, yes, even with Park Tool’s handy-dandy magnet tool. The phrase, Like sticking an oyster into a slot machine comes to mind. Going wireless would be a boon.
Snaking a steel cable through some housing is, no doubt about it, a whole lot easier. To be fair, however, once those Di2 wires are tucked away in the frame, they are not likely to need replacing for years. In my mucky conditions, on the other hand, I’ll swap out a cable once or twice a year.
Once the wiring was done, it was time to adjust the shifting. It’s absolutely painless. Pushing the Mode button on the visual display sets you into Maintenance Mode. From there, you select which derailleur you want to adjust and then you use the shifter paddles to fine-tune the shifting.
The first thing I took note of is how the Di2 shifter feels just right in every possible way. The adjustable paddles are exactly where I want them, and both the throw and the tactile feel is spot on—if I were blindfolded and had never seen a Di2 system before, I might even tell you that the positive 'ka-chung' of each shift surely comes from a steel cable being pulled through black housing and that there are no servo motors or electricity involved. Shimano has clearly strived to keep the mechanical feel of their, ahem, mechanical system, and aside from the oddly satisfying ''zzzzt'' of the tiny motor doing its job, they definitely succeeded.
How it feels notwithstanding, Di2 doesn't actually shift any quicker than a mechanical drivetrain, and dumping a bunch of gears in a hurry to get to a larger cog actually takes more time to do than with Shimano's standard XT drivetrain. While a mechanical XT shifter can jump up through four cogs with the full push of a thumb paddle, XT Di2 is a one-click, one-cog kind of operation. Sure, you can hold the paddle down and Di2 will run up through to the largest cog, but the action isn't as fast as smashing up through the gears with a mechanical setup.
But while XT Di2 might not move the chain with quite the same urgency, there is absolutely zero smashing involved. Quite the opposite, actually, with it offering metronome-like precision for Every. Single. Shift. You and I both know how to shift, of course, but I think we've forgotten that it certainly does take some know-how, especially from drivetrain to drivetrain and knowing just how far to push the thumb paddle. This is basic stuff, yes, but stick a neophyte on your bike, point them towards some sharply undulating terrain, and they're going to f*ck it up. With Di2, however, you literally can't do anything wrong; pushing the paddles will do exactly the same thing every time, no matter what. It's next-level consistency, really, which is impressive given that the bike was abused, often covered in a week's worth of mud and grime, and pressure washed with the kind of recklessness that can only come from someone actively trying to trouble Di2. But I couldn't and now I feel a bit defeated; like the damn robot has beaten me.
Again, I was running both derailleurs off the right-hand shifter, which frees up room for a dropper-post lever on the left-hand side of my bars. The basic idea behind Synchro shift is that, in any multi-ring drivetrain, there are a bunch of redundant gear combinations—many of them awkward combos that have the chain running at crazy angles. Synchro shift basically eliminates the shittier, duplicative gear combos, while affording you the full gear range of a dual-ring setup. Sweet! It accomplishes that feat by automatically shifting the front derailleur as you run up and down the cassette. Wait! What the f*ck?
Automatic front shifting? That sounded crazy to me, as if Shimano's computer was suddenly calling the shots. I mean, what if that computer and I disagreed at a key point in the ride when I didn’t want to be talking to a computer at all?
Amazingly, Synchro mode works brilliantly. You aren’t surprised that a front shift is going to happen because the system beeps at you when you are one rear derailleur shift away from the front derailleur bursting into life. Moreover, front derailleur shifts are natural and smooth, even under heavy pedal loads. I prefer the simplicity of a 1x drivetrain, but if I used a front derailleur, I’d only run it in Synchro. Rear shifting has proven flawless from day one. After about five rides, however, the front derailleur began struggling to hoist the chain from the small to large chainring. On downshifts (and particularly chunky descents) I was also starting to drop the chain onto the bottom bracket.
Solution? I simply entered Maintenance Mode and used my shifter paddle to reposition the front derailleur; that remedied the weak shifts to the big ring. Front and rear shifts have been perfect ever since. I still encounter the occasional dropped chain on particularly fast and technical descents; frequency-wise, it's about par for the course for a front derailleur system. After four years of running 1x drivetrains, however, I have little tolerance for that kind of thing. So, while I am impressed as hell by Synchro, I’d personally opt for the single-ring version of this group.
Shimano used to get slagged for not providing riders with options, but Di2 opens up all sorts of options. In my case, I could choose to use two shifters, or just one, to operate both front and rear derailleurs. Riders can also use their computer, iPad or smart phone to tweak shifting speeds and, if you are running a front derailleur, to adjust the points in the shifting process when the front derailleur kicks in (in Synchro mode) and does its magic.
While I personally prefer the simplicity (and lack of dropped chains) of a single-ring drivetrain, I'll readily admit that the front derailleur has achieved its apex of performance when operated in Synchro mode. You essentially use a single shifter, just as you would with a 1x set-up, and the front derailleur kicks into life at the right moments, to provide you with a wider gear range. Moreover, it does the auto shifts magnificently well. I had to ride it (a lot) to believe it.
Nothing to gripe about here. I've had the XT Di2 system on my Rocky Mountain Element 990 RSL BC Edition since December, enough time to completely wear out the stock Shimano chain, and have had absolutely zero reliability concerns. No amount of water has been able to give the electronics any trouble, and nothing has disconnected since I managed to sort out the install. Hell, I only just had to charge the battery a few days ago, after roughly four months of use. A typical B.C. winter and spring will usually see me change a few shift cables in that time, depending on the bike, but the XT Di2 has made exactly zero fuss.
A well-maintained cable-driven derailleur is dead simple to operate, but I will concede this: With Di2, Shimano has created a system that does not degrade in performance—no matter how much you abuse it. That’s no small thing. Mud, water, general mean-spiritedness… none of it fazed this robot version of Shimano XT. Push on the paddles and you are rewarded with a firm click and a perfect shift. Every. Damn. Time. While I was initially concerned about battery life (the front derailleur uses more juice than the rear derailleur), I squeezed in two months of riding before I needed a recharge. You won't suddenly lose power out on the trail; it's a non-issue.