Shimano launched their first electronic transmission, Dura-Ace Di2, four years ago. After it garnered rave reviews and proved itself a viable alternative to traditional mechanical shifting, they brought the technology down to a lower pricepoint last year with Ultegra Di2. The logical next step would be offering Di2 at the next rung down the road groupset ladder, 105.
Instead, Shimano have gone in a different direction: Di2 hub gearing. And in many ways this makes sense. There's no need for a front derailleur or left-hand shifter, which should bring prices down to a more affordable level (exact figures have yet to be confirmed), and instead of a vulnerable (and expensive to replace) rear derailleur, the gear changing mechanism is encased in the rear hub, out of harm's way.
In addition, electronic shifting would seem ideal for the high-end urban/touring market the Alfine hubs were designed for, offering low maintenance (regular charging but no issues with cable stretch or contamination), simple operation and sleek looks, with the wiring run through the frame.
The system consists of a Di2-specific hub with either eight or 11 speeds, a choice of RapidFire Plus flat-bar shifter or drop-bar dual control levers (these come as a pair but the left-hand one has no gear paddle), a battery and the same modular E-tube wiring used on Ultegra Di2 (which uses narrower cables and connectors than Dura-Ace Di2). The number of possible shifts is dictated by the hub, not the shifter, which merely sends electronic pulses.
With Shimano Alfine Di2 there's no front mech so the right-hand lever (ST-S705-R) has a shift paddle but the left-hand lever (BR-S705-L) handles braking duties only
Cables can be fully internally routed and the battery can be mounted externally (either on bottle cage bosses or specific fittings) or internally. At their 2012/13 UK launch in Birmingham, Shimano showed an example of a battery concealed within a seatpost. The seat tube is another option – the company say it's up to bike manufacturers to decide where they want to put it.
Shimano are working on a digital display for both Alfine and Ultegra Di2 which will show gear and battery life. The version in our photograph is a prototype and was snapped while design work was still ongoing. We'll bring you more information on Alfine Di2, including pictures of the finished product, here on on BikeRadar as soon as we get it. It's due to begin shipping in September 2012.
At the time of their 2012/13 launch, Shimano were still tweaking the design of their digital gear display