Shimano Dura-Ace Di2 electronic: first ride

Can Shimano succeed where others have failed?

Shimano’s Dura-Ace Di2 electronically-controlled shifting system is finally here. We rode the new gear at its launch at the legendary Formula 1 race circuit in Suzuka City and just to make things interesting Mother Nature saw fit to provide buckets of driving rain. Game on.

Shimano claims its new shift-by-wire system is effectively faster than old-style cables (we’ll explain in a bit), requires less effort, and far less finger movement. The gradual performance degradation caused by cable housing wear or contamination is completely eliminated (as Shimano puts it, “the input always equals the output”).

Big claims indeed. What we wanted to know was simple; how does it work on the road

Zoom zoom

Di2 is jaw-droppingly smooth. Even the standard all-mechanical 7900 Dura-Ace group almost seems clunky in comparison and SRAM’s top-tier Red group just can’t compare. Our early impressions are that Di2 ushers in a previously unheard-of level of shifting precision and refinement.

The di2 lever doesn't just look smaller than 7900; the body is substantially smaller in girth and it's also 100g lighter. : the di2 lever doesn't just look smaller than 7900; the body is substantially smaller in girth and it's also 100g lighter.
Di2 vs 7900 levers

The 7900 Dura-Ace group uses the same system of pins, gates, and ramps as Di2 so you might not expect much of a difference. But while the mechanical drivetrain is just as capable of knocking off similarly smooth shifts under ideal conditions, Di2 makes nearly every shift so dead-on perfect that it’s almost eerie.

Instead of forcing the chain on to larger cogs or rings at less-than-ideal times as we often do with mechanical shifting, Di2 basically only shifts at the designated gate and it seems to hit its mark almost every time.

Front shifts in particular are remarkably well controlled. While 7900 opts for a slightly wider front derailleur cage to eliminate the need for trim, Di2 sticks to a narrower dimension for more precision and squelches the rub by automatically tweaking the position depending on rear gear selection.

For example, when in the inner chainring and largest rear cog and then shifting to the outer ring, Di2 first adopts an intermediate position that allows the chain to cleanly grab the ring without overshifting and then finishes the rest of the movement just afterward so as to eliminate cage rub.

This will be a more common sight if shimano gets its way. : this will be a more common sight if shimano gets its way.
D12's brain is surprisingly clever

The CPU also quickly realizes that you’re now in a cross-gear combination and then readjusts the cage back inwards a hair to squelch rub on the inner cage, just as you would do yourself.The reverse happens when shifting in the opposite direction. Clever.

Unlike mechanical systems though, even rear shifts use a two-step motion, at least for upshifts. The rear derailleur overshoots slightly to grab the smaller cog a little more quickly and then tweaks the cage back over to quiet things down.

Di2 doesn’t actually shift the chain from cog to cog faster than 7900. Since shifts are now even more dependent on the location of the timing gates on the cogs and chainrings it’s arguably a bit slower if anything. However, the time savings come more in the reduced delay from lever input to derailleur output. It’s a subtle difference for sure but one that’s tangible nonetheless (again, don’t scoff until you’ve ridden it).

Multiple shifts honestly surprised us. There’s no built-in mechanism to trigger multiple shifts. You can’t slam the shift lever across several clicks. But the button throws are so short that you can rattle off as many shifts as you want with little issue. Galaga champions: your time has come.

As intelligent as it is, Di2 can still be confused but you really have to ride it as if you’re intentionally trying to break it. Like if you dumped six gears in one direction and then went three gears in the opposite direction before the system had completed the first set of commands. While out of the saddle and in a full sprint. And shifting up front at the same time.

Of course, that scenario is purely hypothetical because we’re far too responsible to even dream of treating a test bike this way…

Lay your hands on me

The button throws are fantastically short but they still require a relatively firm push thanks to the collection of springs that lie behind them. : the button throws are fantastically short but they still require a relatively firm push thanks to the collection of springs that lie behind them.
The button throws are fantastically short but they still require a relatively firm push thanks to the collection of springs that lie behind them.

The Di2 Dual Control levers are markedly different in feel and shape from 7900: they’re smaller in girth and slightly more rounded. According to Shimano, 7900’s bigger dimensions were dictated by engineering requirements (and therefore not entirely by choice) as the shifter guts were relocated into the body.

Di2 had no such restrictions so its shape is more in keeping with Shimano’s ideal. It still retains the flatter perch that we found so welcome with 7900 so it’s still a notable improvement over 7800’s ergonomics.

Unlike earlier prototypes though, our pre-production test samples omitted the small LCD displays for gear selection and battery power; that space is now reserved for the optional FlightDeck computer modules. (‘Pre-production’ in Shimano terminology means the bits were made on final production tooling but just hadn’t gone through the quality control process yet.)

Button placement, however, leaves something to be desired. Although one button per lever wears a distinct texture on its surface, they’re still hard to differentiate in the saddle even with bare fingers (let alone with full-finger gloves) and they’re almost wholly lacking in tactile feedback of any sort when pushed.

Moreover, though they’re offset fore-aft and side-to-side and also rather elongated, they’re still arguably too small and seem far too close together. Even as seasoned Shimano users, we mis-shifted Di2 with alarming frequency (albeit with stunning precision).

Shimano claims a dead battery can be fully recharged in just an hour and a half. : shimano claims a dead battery can be fully recharged in just an hour and a half.
Shimano claims a dead battery can be fully recharged in just an hour and a half.

Unfortunately, not only do the same problems exist when your hands are in the drops but new ones crop up. The fore-aft offset is a reasonable approximation of mechanical STI levers while in the hoods (really, it is; go check out your current Shimano setup) but down below you can’t simply reach a finger out to flick the very tip of the brake lever anymore. The downshift button doesn’t reach down that far and you have to curl your finger upward to reach it. Last we checked our fingers didn’t bend that way all that easily and we’re willing to bet that yours probably don’t, either.

To be fair, we weren’t able to spend nearly as much time on Di2 as we would have liked and many of our lingering questions will have to wait until proper test samples begin arriving in a few weeks’ time.

If there’s a mental adjustment period required with Di2, we didn’t reach the end of it during this trip. Even so, the button actuation doesn’t seem terribly intuitive and considering Shimano’s engineers probably could have put the buttons virtually anywhere, the final locations seem to be needless analogues of the mechanical system that unfortunately didn’t translate as well as they should have.

Our limited time also provided little real world information on battery performance although the fact that it didn’t immediately roll over and die in the pouring rain was encouraging..

Shimano’s own “conservative estimate” says the 7.4V Li-ion battery will run for at least 2000km per charge and will withstand 500 charge cycles before exhausting its usable life. However, Shimano also had no answer for us on exactly how many shifts it estimated would be made during those 2000km and the LED battery indicator provides only a relative approximation of remaining charge rather than a more informative absolute display.

Wave of the future or stuck in the starting gate?

Cyclists are undoubtedly a funny lot. While the majority of us have heralded the rise of fancy carbon frames, new metallic alloys and other tech-heavy developments, the idea of using something other than a comparatively ancient steel cable running through a plastic-lined housing strikes most of us as anathema for whatever reason (and let’s not even get into the discussion of how we’re still clamping on those scandium-enhanced rims with small blocks of rubber).

Think of it this way: in this day and age, how many of you would agree to revert back to non-power assisted steering or brakes in your car? Or alternatively, take a look at the specs for your car’s throttle system to see whether it’s controlled by a few strands of cable or a copper wire carrying a bunch of electrons back and forth. You might be surprised.

Di2 does seem to work in the wet.

Shimano naturally has remained steadfast in the position that its new SEIS (Shimano Electronic Intelligent System) technology not only offers more performance than traditional cable-actuated transmissions but that electromechanical designs have the potential to eventually take over mechanical systems altogether someday.

While the new Di2 initially strikes us as an impressive package that could perhaps benefit from a few relatively minor ergonomic changes, the shifting performance is undeniably superior so Shimano’s long-term vision might hold merit if it’s willing to see it through.

Even Shimano might not be able to overcome one of the concept’s inherent drawbacks though. Much as automakers have struggled with this (especially with power assisted steering), there’s an inherent tactile disconnect in an electronically controlled system that can be so critical especially at the enthusiast end of the spectrum.

Di2 is incredibly fast and precise but when it comes down to it, there’s no real feedback in your hands as far as what’s going on in the drivetrain and any sort of device that could be built in to offset this would invariably add weight to the system.

Then again, the added performance might just trump everything. Computer-controlled paddle shifters have undoubtedly removed some of the driver interaction in Formula 1 as compared to standard manuals but if you ask Renault driver Fernando Alonso (who won at the Suzuka circuit the last time the series visited here in 2006) which he prefers, the answer will probably be rather direct: “Which is faster?”


James Huang

Technical Editor, US
James started as a roadie in 1990 with his high school team but switched to dirt in 1994 and has enjoyed both ever since. Anything that comes through his hands is bound to be taken apart, and those hands still sometimes smell like fork oil even though he retired from shop life in 2007. He prefers manual over automatic, fizzy over still, and the right way over the easy way.
  • Discipline: Mountain, road, cyclocross
  • Preferred Terrain: Up in the Colorado high-country where the singletrack is still single, the dirt is still brown, and the aspens are in full bloom. Also, those perfect stretches of pavement where the road snakes across the mountainside like an artist's paintbrush.
  • Beer of Choice: Mexican Coke
  • Location: Boulder, Colorado, USA

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