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Shimano began drastically changing the designs of its mountain bike rear derailleurs in 2007, moving the entire mechanism toward the rear of the bike in an effort to improve shifting performance and chain wrap on wider-range cassettes. That design quickly filtered out to Shimano’s entire mountain bike range, although there now looks to be a course correction with the latest XTR groupset) – but not before Direct Mount migrated over to the road with the introduction of the Dura-Ace R9100 groupset in 2016.
Shimano was able to move the derailleur rearward by adding a short aluminum link. Somewhat ironically, the design was dubbed “Direct Mount”, despite the fact that that additional piece made it anything but. However, Shimano’s intent has always been that frame makers would use dedicated rear derailleur hangers to bypass that stopgap altogether.
In addition to helping reduce the clutter back there, the claimed benefits of using a proper Direct Mount hanger included more precise shifting (since the mount would presumably be stiffer than two pieces bolted together) as well as faster wheel changes, since there would now be less stuff standing in the way of the rear hub.
Adoption of dedicated Direct Mount hangers has been pretty slow off-road, and positively glacial in the road world, but you wouldn’t know it by looking at the bikes of this year’s Tour de France. Of the 22 teams in the race, 17 are running Shimano groupsets, and more than half of those teams are running proper Direct Mount hangers on their bikes. Even more interesting is the fact that several of those teams had to have those hangers custom machined since their bike sponsors don’t even normally offer the option.
Shimano didn’t have much to say on the topic when I asked for an official statement, but team representatives I spoke with cited the claimed benefits: better shifting and faster wheel changes, the latter being especially critical on bikes equipped with disc brakes and thru-axles. It’s worth noting, too, that many of the Direct Mount hangers were conspicuously stout in their construction, with beefy cross-sections that would not only provide a firm foundation for precise shifts, but would likely be less prone to bending during a crash.
Might this be a sign of things to come? Will we start seeing more Direct Mount hangers on consumer road bikes in the near future? We’ll have to wait and see, but seeing as how the teams using them were apparently more motivated by performance gains than any sort of pressure from an equipment sponsor, there seems to be some merit to the idea.