Shimano Dura-Ace 9150 Di2 Rear Derailleur
The most striking change to the new Shimano Dura-Ace 9150 groupset is undoubtedly the rear derailleur. The new design has a uniquely angular design that borrows the Shadow RD low-profile design that's been popular on Shimano's MTB derailleurs for a while? MTB derailleur technology on the road? Crazy we know, but the improved shifting performance and chain retention make it well worth it. The derailleur keeps the same unmatched shift quality and smooth performance even under torque of previous iterations, but now introduces Syncro Shift customizable shifting. First introduced on XTR Di2, Syncro Shift again changes the way bikes will shift gears. The feature (which can be disabled and customized) simplifies shifting by automatically shifting the front derailleur in certain gear combinations to help the rider maintain optimal cadence and power. At just 204g and the ability to now handle up to a 30T cog, the 9150 Di2 groupset is both a revolution and an evolution in electronic shifting.