Shimano has officially unveiled Dura-Ace Di2, an 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 with components from the 7900 series Dura-Ace group while adding only 68 grams to the entire groupset. Dura-Ace Di2 will be available in January 2009.
According to Shimano, 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 thus effectively switches which also allow 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 synchronized and calibrated shifts every time.
By using unidirectional carbon fibre 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.
Like the 7900 mechanical derailleur, the 7970 has a new carbon fibre rear pulley cage and the new design is compatible with wider range cogsets, accommodating up to a 27 tooth cog. The unit is now driven by a servo motor instead of a cable and spring, so shifts are identical and precise 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.
According to Shimano, 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.
The 7.4V, high performance lithium ion battery is designed to deliver reliable and long life performance even in the worst conditions. In conditions requiring consistent and frequent shifting, the battery is capable of 1000 kilometres of use. The battery is rechargeable and comes with a mount that 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.
According to the company, Shimano’s 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.
