Shimano’s Dura-Ace Di2 shifting system would not be possible without over 20 years of development.
A closer look at shifting
Shimano’s Dura-Ace Di2 shifting system would not be possible without over 20 years of development in all aspects of derailleur, sprocket and chainring design. And now it has a younger brother, Ultegra Di2.
The professionals on Team Sky have benefited all season from the improved gear shifting precision provided by the Shimano Dura-Ace Di2 system. Whether testing the reliability and robustness of the system at Paris Roubaix, or making use of the innovative satellite shifter option in bunch sprints or the high mountains, Dura-Ace Di2 gives Team Sky a concrete advantage.
Dura-Ace Di2 offers rapid and precise shifting because it combines several technologies including carefully selected servomotors, weather proof cabling and the compact CPU housed inside the Di2 front derailleur. But one less obvious aspect makes it all possible: the intricately shaped teeth of the cassette and chainrings, and the matching chain.
Over years of development and countless hours of testing Shimano developed an ultralight shifting action made possible by extremely smooth movement of the chain between individual sprockets. The painstaking reduction of shifting force allowed Shimano to select from a wider range of actuators when designing Dura-Ace and Ultegra Di2. The tooth profiles may not be unique to Shimano’s electronic shift systems but they are certainly a crucial enabling technology without which the technical challenges of producing reliable and precise electronic shifting in a lightweight package would prove significantly more difficult.
Crossing over
Because the ultra-low force shifting of Dura-Ace chain and sprocket systems is also a feature of Shimano’s enthusiast-level Ultegra groupset, the lessons learned in the design of the race-winning Dura-Ace Di2 shifting system could be applied in the design of a more affordable electronic shifting system. Ultegra Di2 shift levers feature the same two-button control method as their Dura-Ace siblings and the servo-motors which drive the derailleurs are still controlled by a central CPU housed inside the front derailleur.
The signals from the push-button control levers now run along slimmer cables which are every bit as weather proof as Dura-Ace cabling but are easier for a home mechanic to install. The Ultegra Di2 derailleurs swap the carbon fibre components of Dura-Ace for aluminium construction to trim costs without sacrificing performance while adding minimal weight. Innovative features such as self-trimming of the front derailleur in response to changes made at the rear have been retained along with the damage limitation system for disengaging the rear derailleur motor if a heavy impact is detected.
With the same low force shifting given by Shimano’s intricate tooth profiling, and the valuable development insight gained from working with pro teams such as Team Sky to refine Dura-Ace Di2, Shimano engineers have been able to maintain the precise shifting and race-winning performance that Team Sky enjoy in the new Ultegra Di2 system. For riders aspiring to emulate Chris Froome’s daring attacks in the Vuelta on a tighter budget, or those seeking more precise shifting for whom the very lightest components aren’t an attraction, Ultegra Di2 offers them the ideal solution.
