Shimano Di2

Our rating 
4.5 out of 5 star rating 4.5

If super-slick aero framesets were the memorable sight of September’s Eurobike, and German sausage the memorable taste, the memorable sound was a cool R2D2-style motor noise. Everywhere you went, it seemed, you could hear the clicking and whirring of a Shimano Dura Ace Di2 mech being fiddled with.


The Di2 adorned nearly every single top-end road and TT bike on display. Having already gained significant traction in the pro peloton during the last year or so, you can now officially bet your bratwurst that it’ll be much in evidence in the seemingly recession-proof confines of triathlon transition areas worldwide during 2010.

For the uninitiated, Di2 is Shimano’s flagship Dura Ace road groupset gone all Terminator. It provides electronic shifters and mechs that claim to make pulling cable a thing of the past when you want to change gear. If you’ve been cycling for more than a couple of years, you might recollect that this isn’t the first attempt at electronic gears. Remember the Mavic Zap System? That was around in the early 1990s and I seem to remember Simon Lessing using it for a while, and running out of battery just before the 1993 World Champs in Manchester! Not long afterwards it faded away, presumably now residing in the same place that Softride bikes and Dave Scott’s moustache can be found.

Di2 is, however, the first really aggressive attempt to make electronic shifting ‘the future’, given that pretty much anything Shimano pulls off successfully seems to become standard cycling issue at some point down the line. Many years, man hours and millions of Yen have gone into its development, as the powers that be at Shimano know that it has to work first time – and every time – otherwise it’ll be thrown on the scrapheap alongside Spinaci aerobars and MiniDisc players.

Basically, rather than pulling or releasing a cable to mechanically change the position of a derailleur, the Di2 system uses tiny motors to move the mech at the push of a button. It makes for a very positive and precise shift, timing the movement to use the ramps and pins of the chain and cassette to best effect. Although the actual speed of the chain moving from sprocket to sprocket is, therefore, not always as fast as can be achieved with a cabled set-up, the whole shift is quicker and smoother from start to finish – it begins the instant you press the button and moves exactly the correct amount every time.

At first it takes some getting used to, but very quickly you learn to appreciate the precision and overall pace of gear change that the Di2 offers. The kid in you will also love the buzz of the motor moving, which sounds very hi-tech. 

There are a few other unique things about the Di2 which are subtle but quite impressive, such as the front mech cage size. On the ‘normal’ Dura Ace set-up the cage is a little wider than average to reduce rubbing when on the extremes of the block, but the Di2 manages to use a narrower cage (for more precise shifting) by automatically trimming the front mech when the rear changes.

Weight-wise the Di2 set-up is a fraction heavier than regular Dura Ace 7900 – 68g, to be precise – due to the weight of the battery. The mechs are heavier than regular versions but this is offset by the shifters being really light, so the net difference is minimal. The battery life is good for at least 1,000km and up to 2,000km, depending on the terrain and, therefore, the number of gear changes needed. In fact, rumour has it that the Garmin Slipstream team only recharged their Di2 units once during the whole Tour de France, and with a one-hour charge time this suggests ownership should be hassle-free. The units have been tested in variable environmental conditions and even survived a lot of cyclo-cross racing, so would seem to be robust enough for most of us.

The brakes, chainset, hubs, cassette and chain are all regular Dura Ace fare, thus offering compatibility with other parts of Shimano’s range. This also means you can upgrade a bit at a time.

The Di2 shifters instantly feel quite normal to anyone familiar with Shimano STI. The buttons that replace the shift levers are in the same places, but now they only need a light tap to make a shift happen, rather than requiring a physical movement of the lever itself. Shimano seems to have got it just right with the pressure needed: it’s difficult to accidently press the button and shift when you don’t want to but, somehow, when you do want to it feels effortless to change.

The levers are slightly slimmer than standard STIs and are ergonomically comfy as a result. The TT and triathlon set-ups have a couple of tiny buttons that can be mounted on the end of the tri-bars, and also near the brake hoods, meaning shifting in or out of the saddle is possible – a real advantage over traditional bar-end shifters.

As previously mentioned, the shifts are precise and fast every time. Even under load it doesn’t miss a beat and, despite the fact you can’t sweep the lever for multiple shifts at once, a series of quick taps on the button does the job just as quickly and with more accuracy. To get anything like a malfunction you really have to do silly things like shift seven gears on the back while changing from the small to big chain ring (or so I’m told… I wouldn’t dream of abusing a test bike in such a manner!). In fact, it’s fair to say that after just few rides using the Di2, getting back onto a cabled set-up, especially one that’s not been professionally installed and tuned, does feel decidedly clumsy and second-rate.

The only negatives really come down to aesthetics and cost. With the battery pack, battery level indicators and bulky mechs, the Di2 still looks a little prototype at this stage. Many top manufacturers, including Cube and Trek, are already building framesets with special holders for Di2 batteries and internal routing for the wires that’ll really help here: at the moment, as a retro fit to a standard bike, there will always be some cable ties and tape involved in making it all work.

Price-wise, it’s undeniably expensive. At over two-and-half grand Dura Ace 7900 Di2 complete system or £1705.92 for just the electronic elements (that can be paired with some existing Shimano parts), it’s a case of ‘sponsored athletes and investment bankers only’ at the moment. But this is probably a temporary situation. Shimano’s own Ultegra and, probably, 105 groupsets will no doubt see elements of the same technology introduced before long – and there are also rumours of Campag and SRAM following suit soon.

So, Shimano should be commended for being first out of the blocks with such a fine piece of technology. The mind boggles as to the number of issues and bugs they must have come across, and subsequently triumphed over, to produce the Di2 to such a high standard of functionality. If the kit turns out, long-term, to be as reliable as the evidence of this short test suggests, there’ll definitely be a long term place for Di2 technology in the future


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