For two years running, Shimano has been testing its electric front and rear derailleurs-and teasing us with vague release scenarios. Today, Shimano announces that its Dura-Ace Di2 battery-powered shifting system will be sold to the public (and standard on select production models throughout the world) as early as January 2009. Di2 consists of five components: a pair of shift/brake combination levers, a rechargeable Lithium-ion battery pack, and a front and rear derailleur. Di2 is compatible with all 2009 Dura-Ace drivetrain components and thus, is upgradeable for Dura-Ace owners caught short in the race to own the ultimate technology.
Here’s the official release:
Shimano Turns on the Power with 2009 Dura-Ace Di2 Electronic Shifting Option for 7900 Series
Dura-Ace 7970 Di2 Delivers the Most Precise Road Shifting Ever While Remaining Lightweight
Irvine, Calif. (August 1, 2008) Shimano officially announced Dura-Ace Di2, a technologically advanced, electronic shifting option for the all new 7900 series Dura-Ace. Comprised of Dual Control type shift / brake levers, front derailleur, rear derailleur, and a battery pack, the new Dura-Ace Di2 7970 components provide precision electronic performance and integrate seamlessly with components from the 7900 series Dura-Ace group while adding only 68 grams to the entire group.
Electrically actuated shifting significantly eliminates issues associated with cable friction and contamination because the derailleurs respond to electrical impulses that are delivered in fractions of a second. The shifters are now merely switches which also allows for creative placement of optional remote shifters while also reducing the weight and profile of the main shift units. Derailleur movement is precisely controlled through computer automated movement and servo motors creating perfectly synchronized and calibrated shifts every time.
ST-7970 Dura-Ace Di2 Dual Control Levers
By using unidirectional carbon fiber brake lever blades and eliminating all of the mechanical shifter parts, the new Dual Control lever weight is reduced by over 155g over the mechanical version. The ergonomics are slimmed down and further refined for a comfortable grip.
The wiring harness for the shifters is designed to accept the all new FlightDeck computer (SC-7900) featuring heart rate, altitude, grade, cadence, estimated caloric consumption, gear position, and battery life all directly downloadable data via a wireless connection.
RD-7970 Dura-Ace Di2 Rear Derailleur
Like the 7900 mechanical derailleur, the 7970 has a new carbon fiber rear pulley cage and the new design is compatible with wider range cogsets, accommodating up to a 27 tooth cog. The differences are the fact that the unit is now driven by a servo motor instead of a cable and spring, so shifts are identical and precise every time as the computer control unit analyzes each shift.
The derailleur has a built in mechanism that will allow the body to move inward under impact to reduce the potential for damage in the case of a crash. Cycling through the shifting a couple of times allows the shifter and rear derailleur to automatically re-synchronize.
FD-7970 Dura-Ace Di2 Front Derailleur
The front derailleur is the ‘brains’ of the system. The integrated ultra-compact CPU not only ensures that shifting is perfect for both the front and rear derailleurs individually, but also by monitoring the position of each, creates a front derailleur that tracks the chain and requires zero manual trim without sacrificing any shifting speed. The front derailleur logic also performs the inward shift from the big chainring in two parts to eliminate chain drop, with both actions measured in fractions of a second.
SM-BTR1 Dura-Ace Di2 Battery Pack
The 7.4V, high performance Lithium Ion battery is designed to deliver reliable, long life even in the worst conditions. In conditions requiring consistent and frequent shifting, the battery is capable of 1000 kilometers of use.
The battery is rechargeable and comes with a mount that easily adapts to most bikes. Lithium Ion technology is lighter, more compact and better performing than other power sources, making it a clear choice for Di2.
Dura-Ace Di2 redefines the highest level of component performance and solidifies the brand as the benchmark for professional cyclists and road cycling enthusiasts alike. Dura Ace Di2 will be available January 2009.