Shimano has used Shadow technology for years on its mountain bike rear derailleurs. It allows for a lower profile and places the derailleur further inboard, keeping them out of harm's way and allowing a better chain path off the top jockey wheel in relation to the cassette. Shimano's R9100 group is the first time we saw this technology carried over to the road side, and we're happy to see its inclusion on the Ultegra RD-R8000 rear derailleur.
The RD-8000 is the crowning jewel on the new Ultegra group, and if you are building up or updating a bike, you really can't do wrong with this group. The additional range afforded by the longer cage opens up the Ultegra group to adventure bikes and brings the precision, durability, and value to the masses. Additionally, if you just want to add a wider range to your Dura-Ace steed, adding the long cage Ultegra derailleur and cassette is all you need to spin perfect circles up long mountain passes. The shifting is impeccable, the durability is immaculate and the performance gap to Dura-Ace is about a tire width's margin in a bunch sprint.
The change to an aluminum cage and some other minor hardware details are all that separate the Ultegra R8000 version from the Dura-Ace 9100 unit. Two cage lengths are available with cassette ranges from 11-30t (short) and 11-34t (long). Given a few design tweaks, the R8000 rear derailleur works best when paired with R8000 or R9100 levers, and it's a perfect addition to a full Ultegra bike or those running Dura Ace who want to run a bigger cassette.
Another advantage of the Shadow design is the more linear path of the derailleur when shifting, which allowed the engineers at Shimano to create a shifter with a shorter throw resulting in more precise and quicker shifts—even with the larger cassette ranges we're beginning ride on everything from tarmac to gravel. We are happy to see Shimano continuing with a barrel adjuster at the derailleur. Road shifters don't have adjusters at the levers like mountain bike shifters do, and not all of us are fans of in-line adjusters.
Shimano's wizardry in manipulating aluminum creates bodies, pivots, and cages that are strong and light. Precision bushings allow smooth movement and ensure proper indexing, and the alloy cage aids in stiffness, helping to improve the shifting response and adding durability—a trait all the more important now that we're also abusing Ultegra on gravel and dirt.