2012 Shimano Dura Ace TT-7971 Di2/7900 Group (Time Trial)
Shimano unveils the Dura-Ace Di2 to complement the Shimano DURA-ACE Di2 Time Trial series. Di2 stands for Digital Integrated Intelligence, an electronic shifting option for the all-new 7900 series Dura-Ace. This innovative shift technology is still based on the Shimano Index System. The big difference is that in this case, the shifting action is provided for by electronics instead of mechanics.
Composed of bar end shifters SW-7971, brake levers (ST-7971), front derailleur, rear derailleur, a wiring harness and battery pack, the new Dura-Ace Di2 7971 TT components integrate with components from the 7900 series Dura-Ace group.
Shimano Di2 Front and Rear Derailleurs
Just pushing the button will shift the front derailleur completely effortless and smooth, even under high load. An additional feature is the automatic trim function. The chain guide moves automatically in response to the setting of the rear derailleur. The rear derailleur offers remarkable quick and smooth shifts. It has a wide gear ratio (11-27T compatible), and the electronics are well protected from heavy impacts such as crashes. The rear derailleur features a carbon pulley plate and titanium B axle for increased weight savings.
Shimano Di2 Battery
Dura Ace Di2 uses a 7.4V Li-Ion battery that is compact and powerful. Excellent reliability and a long lifetime has been proved through repeated field tests in various riding conditions over the last two years. The battery is very easy to mount and remove for charging, and it fits any kind of road bike. The shifting system is not wireless since that would a much heavier battery.1612