Shimano Dura-Ace Di2 Electronic Rear Derailleur

Shimano Dura Ace Di2 Electronic Rear Derailleur:
No more barrel adjusters or springs. In fact all the adjustment of the rear derailleur is done through the Shimano Di2 STI levers! No more shifting by the use of a spring, rather the rear derailleur moves in a programmed motion by knowing the spacing between the cogs. Simply remarkable.

Each shift is completely clean. The rear derailleur will lift the chain during the shift placing it perfectly onto the next cog of your cassette. It then will center itself perfectly underneath that cog. Extremely fast and crisp shifting powered by servo motor driven worm drive which replaces the old-fashioned spring system.

The Shimano Di2 rear derailleur also has a servo saving feature that in the event of a crash will move the rear derailleur as far inward as possible to avoid damaging. You then get back up, dust yourself, hop back on your bike, shift a few times and the rear derailleur will auto-adjust by itself! If that doesn't work you'll have to do the on-the-fly adjustment using a button on the wire harness. This take you through a series of shifts till you completely back in tune and ready to fly!

Specifications:

Programmed, electronic motion

Requires the rear derailleur wiring kit

Short-cage only

222 grams

Shipping Weight: 1.5 lbs.