So, on the subject of this whole Direct Mount hanger business...
1. The new 9100 derailleur, and I presume the new Ultegra rear derailleur, both have removeable "b-links", correct? This b-link, which I used to refer to as the "extension thingy", is essentially there so that when attached to a regular hanger the derailleur is positioned in the same place it would be if it was attached to a Direct Mount hanger after removing the b-link. So why the fuss over wheteher there is a DM or a regular hanger?
2. If frame manufacturers only made DM hangers then that would mean SRAM and Campagnolo rear derailleurs could not be used with these frames, unless there was another hanger available to be swapped out. Not good. As it is now, the b-link is provided for current hangers. So what is the advantage of creating frames with a hanger that will not work with SRAM or Campagnolo rear derailleurs? Or more generally, what is the advantage, period?
3. Is it better? So far, the new 9100 rear derailleur has left me with quite mixed feelings. I suppose it's better if you want to run pie plate type cassettes, after all... the design is carried over from their mountain bike stuff. But it doesn't seem like they thought through some of the practical issues this design presents to a lot of road bikes. Specifically, I'm talking about rear wheel removal. With some road bikes, especially ones with fairly substantial Bottom Bracket mouldings, it is a royal pain in the ass to do a simple rear wheel removal. The derailleur just does not want to move out of the way enough to allow the wheel to slide out. With mountain bikes there's usually a ton of clearance up front of the tire between the bottom bracket. Also, BB drops aren't as large as on road bikes. So on mountain bikes this issue is moot. But with road bikes and quick release wheels, that wheel needs to both drop down and slide forward a substantial amount to clear the derailleur and in some cases all kinds of jamming up occurs due to the rear derailleur not being able to move easily out of the way. Add to this that some folks want to run larger tires and the problem gets worse.
4. I suppose through axles and longer chainstays to accommodate bigger tires would help all this, but where does the mountainization of the road bike stop, or does it? I like the fast elegant quick release and easy removal of the rear wheel. I think Shimano needs a few tweaks to their latest rear derailleur design before I'll start jumping up and down praising its virtues because so far this single aspect of it is proving to be a big negative. Rear wheel removal should be an easy operation on any frame, or at least no more difficult than it ever was. If it's not, then someone has messed up in their design process. Fix it Shimano. Please, fix it.