IRVINE, CA (BRAIN)—After years of testing Shimano brings its Dura Ace electric drivetrain, Dura Ace Di2, to market.
Sold as an optional upgrade package to mechanical 7900 Dura Ace, Shimano expects to deliver Di2 Dual Control type levers, front derailleur, rear derailleur, battery pack and charger kits to retailers and OEMs in January.
“Going electric helps to ensure precision that can make a rider faster and reduce mental fatigue. If you think about Formula One racing, the race cars use automatic and clutchless transmissions because the computer can create a faster, more synchronized and consistent shift than a skilled driver can manually,” said Devin Walton, Shimano’s public relations manager. “That being said, those same technologies can improve performance for anyone and there is a certain novelty factor for those enthusiasts that like to indulge in the latest high tech equipment or use the same equipment that professionals use."
Since there are no mechanical guts inside the ST-7970 Dura Ace Di2 levers, they have been slimmed down and have a new ergonomic feel—and they are 155 grams lighter than Dura Ace mechanical levers. The new FlightDeck computer (SC-7900) with heart rate, altitude, grade, cadence, estimated caloric consumption, gear position and battery life drops right into Di2 levers. Electrically actuated shifting significantly eliminates cable friction and contamination because the derailleurs respond to electrical impulses that are delivered in fractions of a second.
“The shifters do have some articulation for the benefit of the human interface feedback loop. But they really are just buttons that are designed to operate in a manner similar to traditional STI so that the transition from mechanical to electronic would be very intuitive,” said Walton. “We will have optional buttons that could be mounted elsewhere on the bars and we’ll also have TT specific buttons such as those seen in the Tour.”
An ultra-compact CPU is hidden inside the FD-7970 Dura Ace Di2 front derailleur to manage front and rear shifting. Also by monitoring the position of each derailleur, it moves the front derailleur to track the chain and requires zero manual trim without sacrificing shifting speed. The front derailleur CPU 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 RD-7970 Dura Ace Di2 rear derailleur, like the 7900 mechanical derailleur, has a new carbon fiber rear pulley cage and accommodates cogs up to a 27 teeth. Because there is no cable, the Di2 rear 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.
Shimano has yet to price the Di2 upgrade package, but it does note that retrofitting the new 7900 mechanical group with Di2 only adds 68 grams to the group weight. Shimano is shooting at having a ridable Di2 equipped bike at Interbike, and would like to have ridable samples at Outdoor Demo, but it knows enough about bringing this long anticipated group to the market not to promise anything.
