Shimano XTR Di2 Review: Can Electronic Shifters Make Bicycles Faster?

Shimano is bringing its electronically-actuated Di2 shifter technology to mountain bikes, claiming increased reliability, faster shift speeds and improved man-machine interface. Can it really make riding a bicycle easier? We spent a day on the trail to find out.

What’s wrong with traditional shifting?

As we identified above, cables are difficult to route, the entire system is subject to damage and dirt ingress and can easily go out of alignment, while putting it back in requires an experienced, deft hand.

Shifting, particularly to larger chainrings, requires some level of finesse and attention from the rider and can otherwise go wrong, leading to a slipped chain.

But Di2 is not so much about addressing failures in mechanical shifting, it’s about finding a new opportunity to increase bicycle performance.

“The challenge was not just to add digital functionality to a mountain bike,” explains Matt. “But to create a logic-enhanced, ergonomically advanced and information driven system that would elevate the riding experience.”

Riding with Di2

“Uphill!” shouted Matt from a couple hundred feet ahead. We were tearing down “The Luge” on Orange County’s Saddleback Mountain in top gear, when suddenly a steep uphill appeared around a blind corner. I had just a couple seconds to get into a low gear or I’d lose all my momentum and fail to make it up. Luckily, a couple of seconds is all it takes for Di2 to make that transition; you just push and hold the downshift button until the shifters reach the gear you want, moving chainrings in the process. I made it up and over and didn’t end up looking like an idiot.

All this talk of buttons doesn’t do the riding experience justice. If you were to hop on a Di2-equipped bike blindfolded, you wouldn’t know you were riding a bike with electronic shifters. Shimano exerted much effort into tailoring the haptic feedback of the shift levers to replicated a manual system. Yes, you’re effectively just pushing a button, with the benefits of speed, accuracy and ease that brings, but you still push a lever that looks and feels and clicks like a mechanical shifter. You’d simply be surprised by the speed and consistency of the shifts, and then you’d crash, because you’re riding a bicycle in a blindfold.

The bike I was riding was a Santa Cruz 5010 C, retrofitted with Di2 shifters. Shimano is making the system in parts, as a groupset and integrating it as a whole into some new mountain bike models. Getting to experience the technology in its most basic form on a nice, but not super high-end XC bike was a good opportunity to evaluate its effectiveness separate from the whizz-bang effect of ultralight wheels and all the other stuff you get with a $US4,300 groupset. Here, it was just a shifter, derailleurs, battery and a display.

That battery mounts to water bottle cage bosses on any bike frame and is about the size of a big Sharpie. The weight of the system will differ slightly with installation and how much of the XTR set you’re paying for, but shouldn’t be responsible for any real weight penalty in any of its guises. While the battery weighs 58 grams, you’re also saving the weight of cables and housings. The entire XTR Di2 system is said to save 50 grams over a similar 2×11 mechanical setup if you opt for a single shifter, which you should.

Allowing that single shifter to sequentially progress up and down gears for you was, to me, the biggest benefit of the system. With it, just set the desired position of the shifter, then decide whether you want the buttons to be top for up and bottom for down or vice versa. Then, you just progress through the gears as normal, the computer simply manages the chainring shifter to give you a totally sequential progression through the available gear ranges. Because moving up or down on the chainring has a larger effect than simply shifting gears on the cassette will, Di2 will adjust that as well; the net effect to the rider is just a linear progression up and down, you just hit one set of buttons to move through what’s, in the case of 2×11, 14 gears. That’s less mental effort and better management of progress than I could manage using my own brain.

With shifts coming so easily, quickly and correctly, you also feel free to shift more often and in more challenging circumstances. Transitions between steep downhills and uphills make seamless a process that was once laborious and you can now shift while tackling rough terrain much more easily. And you’re exhausting far less mental effort even while shifting more, allowing you to focus more on the actual riding with the bike actually working better beneath you.

Going into this test as a mountain bike neophyte, I was expecting neat technology that, judging by the price tag of the XTR groupset, wouldn’t be relevant to my limited riding ability. But, I found completely the opposite. Not only was a I able to ride better with electronic shifting — and feel that difference — but it also helped cover my mistakes and and make the overall ride a little bit easier.

I never would have been able to nail that transition from steep descent to big ascent with a manual shifter. On my own bike, I would have lost all momentum, slowed down to virtually zero, then toppled over. With Di2, I just slid though the gears and maintained my cadence. It couldn’t have been easier.

And any other rider will benefit from Di2 as well. I suggested to Matt that potentially the best application could be for new and casual bicycle riders, who probably find the sheer number of gears intimidating and confusing at a time when they have got better things to be concentrating on. His response was sort of a grimace and a suggestion that they’d probably be ruled out by the cost.

That’s where Di2 lies right now — it’s a genuine, worthwhile advancement in bicycle technology that is, for now at least, only applicable to racers and rich guys. The rest of us will have to watch and wait for the technology to trickle down to more achievable prices.