Amgen tour of California 2012

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Closer look: Shimano Dura-Ace Di2 transmission

  • So, what's the difference? Save for the additional battery, there's little to indicate from afar that this is anything but a standard cable-actuated drivetrain.

    So, what's the difference? Save for the additional battery, there's little to indicate from afar that this is anything but a standard cable-actuated drivetrain.

    Photo credit © James Huang

  • In general, the Di2 levers have a much more finished look and feel about them relative to 7900. We still want more feedback from the buttons and a stiffer paddle but aside from that, it's nearly perfect.

    In general, the Di2 levers have a much more finished look and feel about them relative to 7900. We still want more feedback from the buttons and a stiffer paddle but aside from that, it's nearly perfect.

    Photo credit © James Huang

  • The Dura-Ace Di2 rear derailleur uses the same carbon pulley cage as on 7900.

    The Dura-Ace Di2 rear derailleur uses the same carbon pulley cage as on 7900.

    Photo credit © James Huang

  • All wire connections are extremely tight - we've had no issues with water infiltration throughout testing.

    All wire connections are extremely tight - we've had no issues with water infiltration throughout testing.

    Photo credit © James Huang

  • Even though there's a motor in there, there is still a return spring tucked in between the parallelogram plates.

    Even though there's a motor in there, there is still a return spring tucked in between the parallelogram plates.

    Photo credit © James Huang

  • Custom stick-on cable guides help clean up the appearance and almost completely eliminate the need for unsightly zip-ties. Shimano offers the guides in both black and white.

    Custom stick-on cable guides help clean up the appearance and almost completely eliminate the need for unsightly zip-ties. Shimano offers the guides in both black and white.

    Photo credit © James Huang

  • The button placement makes for intuitive shifting for current Shimano users, at least when on the hoods. Shifting from the drops takes a bit to get used to, though, as the buttons are offset fore-aft instead of the mechanical version's top-bottom positioning.

    The button placement makes for intuitive shifting for current Shimano users, at least when on the hoods. Shifting from the drops takes a bit to get used to, though, as the buttons are offset fore-aft instead of the mechanical version's top-bottom positioning.

    Photo credit © James Huang

  • Brakes cables are easily accessed just by pulling back the brake lever - just like it used to be and a big improvement over the pesky cosmetic cover plate used on 7900.

    Brakes cables are easily accessed just by pulling back the brake lever - just like it used to be and a big improvement over the pesky cosmetic cover plate used on 7900.

    Photo credit © James Huang

  • The Di2 levers use a similar outward cant as on 7900.

    The Di2 levers use a similar outward cant as on 7900.

    Photo credit © James Huang

  • Shimano's new Dura-Ace Di2 electronic shifting is not quite perfect but it's an astounding technological achievement and suddenly makes even the most advanced cable-actuated system suddenly feel primitive by comparison. It's that good.

    Shimano's new Dura-Ace Di2 electronic shifting is not quite perfect but it's an astounding technological achievement and suddenly makes even the most advanced cable-actuated system suddenly feel primitive by comparison. It's that good.

    Photo credit © James Huang

  • The Di2 hoods have less girth than 7900 and the rounded edges make for a more natural-feeling grip.

    The Di2 hoods have less girth than 7900 and the rounded edges make for a more natural-feeling grip.

    Photo credit © James Huang

  • A special tool is included with the group for both installing and removing the cable connections.

    A special tool is included with the group for both installing and removing the cable connections.

    Photo credit © James Huang

  • Unlike on 7900, reducing the reach on Di2 doesn't leave any unsightly gaps.

    Unlike on 7900, reducing the reach on Di2 doesn't leave any unsightly gaps.

    Photo credit © James Huang

  • The rear derailleur is fairly standard-looking save for the bulbous appendage that has sprouted out the back to house the stepper motor.

    The rear derailleur is fairly standard-looking save for the bulbous appendage that has sprouted out the back to house the stepper motor.

    Photo credit © James Huang

  • Small stick-on pads are included to protect the frame in case the front derailleur's additional support screw would otherwise directly push on a carbon tube.

    Small stick-on pads are included to protect the frame in case the front derailleur's additional support screw would otherwise directly push on a carbon tube.

    Photo credit © James Huang

  • Skeptics have voiced concerns over battery life but we can assure you that it's simply not an issue. Even Garmin-Slipstream team riders only charged their batteries once during the entire 2,448km-long Giro d'Italia.

    Skeptics have voiced concerns over battery life but we can assure you that it's simply not an issue. Even Garmin-Slipstream team riders only charged their batteries once during the entire 2,448km-long Giro d'Italia.

    Photo credit © James Huang

  • The battery housing lever pulls the battery in for a tight, waterproof seal and also helps eject it when it's time for a recharge (which only takes an hour).

    The battery housing lever pulls the battery in for a tight, waterproof seal and also helps eject it when it's time for a recharge (which only takes an hour).

    Photo credit © James Huang

  • The bottom bracket cable guide is replaced by a small junction box that keeps things surprisingly tidy.

    The bottom bracket cable guide is replaced by a small junction box that keeps things surprisingly tidy.

    Photo credit © James Huang

  • The Dura-Ace Di2 levers use the same cable pull ratio as on the standard 7900 group, thus providing the same phenomenal braking performance.

    The Dura-Ace Di2 levers use the same cable pull ratio as on the standard 7900 group, thus providing the same phenomenal braking performance.

    Photo credit © James Huang

  • A small control box is attached to the brake housing and provides the interface for derailleur adjustments and battery life indicators.

    A small control box is attached to the brake housing and provides the interface for derailleur adjustments and battery life indicators.

    Photo credit © James Huang

  • The Dura-Ace 7900 crankset's ultra-stiff outer chainring matched to the Di2 front derailleur adds up to the best front shifting in the industry by far and without question.

    The Dura-Ace 7900 crankset's ultra-stiff outer chainring matched to the Di2 front derailleur adds up to the best front shifting in the industry by far and without question.

    Photo credit © James Huang

  • The front derailleur is a bit chunky-looking but it also has to generate a lot more force than the rear derailleur.

    The front derailleur is a bit chunky-looking but it also has to generate a lot more force than the rear derailleur.

    Photo credit © James Huang

  • An additional set screw (centre of frame) is designed to provide an extra bracing point for the front derailleur.

    An additional set screw (centre of frame) is designed to provide an extra bracing point for the front derailleur.

    Photo credit © James Huang

  • Both derailleurs still feature conventional limit screws though they're not in the usual locations.

    Both derailleurs still feature conventional limit screws though they're not in the usual locations.

    Photo credit © James Huang

  • The front derailleur structure is notably stiff.

    The front derailleur structure is notably stiff.

    Photo credit © James Huang

  • When properly adjusted, the front derailleur bracing screw (just barely visible in the centre of the frame) prevents any unwanted twist during shifts.

    When properly adjusted, the front derailleur bracing screw (just barely visible in the centre of the frame) prevents any unwanted twist during shifts.

    Photo credit © James Huang

  • The reach adjust screw is easily accessed by pulling back the lever hood.

    The reach adjust screw is easily accessed by pulling back the lever hood.

    Photo credit © James Huang