Quite a few bikes at Sea Otter had Shimano’s new optional D.R.D. (Direct Mount Rear Derailer), and although the system makes a lot of sense, it is confusing to understand (myself included). Basically, the derailer pivot mounts directly to the hanger, without any B-Link present, and the hanger, which is supplied by the frame manufacturer, sits 20mm aft of a standard one. In the usual setup, the derailer connects to a B-Link, and the B-Link connects standard hanger.
Shimano states that this arrangement provides crisper shifts, greater durability and easier wheel removal and installation? Like many components on a mountain bike, the derailer hanger comes from the road bike arena, and many items, like 9mm quick releases don’t work as well in the more abuse environment. One of the concepts behind a standard replaceable derailer hanger, was that it would break off during a crash or when hit hard, and save the derailer from being damaged. Unfortunately, in real-life use, the derailer gets dragged into the spokes, and get disintegrated. Shimano will release the Shadow derailer ready for Direct Mount, although they will include a B-Link for attachment to a standard hanger. I am not sure whether SRAM will release a derailer that will mount on the Direct Mount?
This useful video has Shimano’s Matt Robertson explaining the new optional standard, along with some of the bike manufacturers who have chosen to adopt this, and incorporate it into their designs. Find out what D.R.D is and see why brands like IBIS, Rocky Mountain, Yeti Cycles, GT Bicycles and Santa Cruz Bicycles are adding the new Direct Mount Rear Derailleur option to their line of bikes.