I just saw a post by Bike Friday head designer Rob English about Ultegra Di2 becoming available on their high end folding bikes. Di2 is Shimano’s electronic gear shift system. The first version appeared on their high end Dura Ace group set used by professional racers. The latest Ultegra Di2 is more affordable, but it’s still not cheap (about US$2,300 vs. $4,000 for the group set). A few months ago my son had the chance to take the Di2-equipped 700C bike of my friend Eric of the GS Astuto team for a spin and simply loved it. Gear changes were so quick and precise and the front derailleur adjusts as you switch through the cassette at the rear. No manual trimming is ever required to avoid chain rub. You never mess up any gear shifts, even under load. Once set up the system remains precisely tuned, with no maintenance required for months.
Some cyclists are skeptical about electronic shifting because it involves batteries. That’s somewhat understandable, since as users of mobile phones and digital cameras we have all experienced running out of charge, often when it’s most inconvenient. However, from what I hear one charge of the Di2 battery should last you about 1,000 km of cycling, far further than the average car fuel tank. A battery that lasts weeks and months should be good enough for most people. What’s more, even if you do run out of power you first get ample warning. For instance, the front derailleur stops working before you will run out of juice for the more important rear derailleur. The ideal setup of course would be electronic shifting combined with a dynamo hub. You would get all the benefits of an electronic system with the self-sufficiency of an all mechanical setup.
After Ultegra Di2, some people were hoping for Shimano to announce a 105 version of Di2 as the next step of digital shifting for the masses (105 is the next road group below Dura Ace and Ultegra), but instead Shimano chose to announce Alfine 11 Di2 (Shimano SG-S705), an electronic version of its 11 speed internal geared hub (IGH), the mechanical version of which had been launched in 2010.
Alfine 11 Di2 addresses the vast city and commuter market, but it should also be interesting for road, touring and mountain bikes. IGHs do without a vulnerable derailleur and require less maintenance. The Alfine 11 gear range (low to high) of 1:4.09 is wider than the 1:3.74 spread of a compact crank (50/34) with a 11-28 cassette. Unlike the mechanical version, Ultegra Di2 does not yet support triple cranks and bigger cassettes can only be done via non-standard hacks.
I recently rode some insanely steep hills west of Tokyo (18-20%), which I could not possibly have managed without the lowest gear of my triple cranks setup (50/39/30 and 11-28 with 20″ 451 wheels). Therefore I think I would be more interested in Alfine 11 Di2, even if Ultegra Di2 will be more appealing to road bike purists.