This thread sort of has me feeling like a kid who can't go out to play till his homework is done. So I will finish what I have to say, since I think it is a worthwhile post to have somewhere on the internet for others. I'll deal with some things @pdlpshr1 just stated in the post above in a bit... but for now that's just a distraction. And before I go any further... I want to repeat... this whole difficulty in wheel removal thing only affects probably a fairly small number of bikes, but it can be annoying to those that it does affect. The new design is good in that it both tries to "wrap" all the cogs as much as possible, even when wide range cassettes are involved. But in order to do so, Shimano wants that attach point to their derailleur body to be set way back from a standard derailleur. Hence they have provided the B-link, as a removable part of the derailleur, but they'd like frame manufacturers to produce a hanger specific to Shimano's needs for all of their frames. So far, frame manufacturers have been slow to go down that route. The B-link attaches to a regular rear derailleur hanger and places the derailleur where it needs to be according to Shimano specs... further back. If a direct hanger is in play, then you don't need the B-link; you just remove the B-Link and attach the derailleur directly to the DM hanger. DM hangers are NOT compatible with Campagnolo or (I presume) SRAM derailleurs. And contrary to what some people seem to think, DM hangers also do not make wheel removal easier. In fact, I can't think of a situation where the new derailleur, regardless of whether it is mounted on a Direct Mount hanger or on a regular hanger with the B-Link will make wheel removal easier than it was before. And this goes for both the new Shimano "Shadow" derailleurs or the derailleurs from Campy since 2015 which incorporate their "Embrace" design. But would I want to return to the designs previous to these... absolutely not. The whole idea behind a rear derailleur is to keep the chain as close to the cogs and wrap as many teeth as possible throughout the cassette's entire range. Do that and shifting is crisp and precise. Can I accept a little more difficulty in rear wheel removal if that can be achieved? Yes, I can. It's just that for some, a little more finesse may be required to remove the rear wheel... and in extreme cases... one may have to let some air out of the tire to do this. But that's really rare. Ok, now that that is out of the way....
Let's first address what @ooo and I were briefly exchanging posts on above. I don't think @ooo's native language is English, but after thinking about his post, I realized that while we were talking about same thing on the hanger (the "hook"), we were talking about two different aspects of it. @ooo was talking about the difference in angle of that hook depending on whether it's a mountain bike hanger or a road hanger. They are different by 10 degrees. That's significant. But I was looking at a very small detail in where the inside radius of that hook meets the main hanger body. I can best show this in pictures and I'm going to use a Camapgnolo SR derailleur and a C59 derailleur hanger as an example to show what I'm talking about. Note: It could very well be that this does not apply to Shimano derailleurs if the stop on the derailleur does not come in contact with the full face of the hook like Campagnolo deraileurs do. On to some pics...
First... A stock Colnago C59 Derailleur hanger on the left, and a replacement hanger provided by Pilo (manufacturer of hangers and other parts based in Israel, they seem to be to Europe what Wheels Manufacturing is to North America)...
Ok... assuming you can see the difference in the "hook" inside radius (the drawn arrows are pointing to the area), then let's have a look how that affects things when a derailleur is actually attached... Campy Super Record in this case... first just a pic of the whole derailleur attached to a hanger (not on bike) so you can get a better idea of what the closeups following are focusing on...
You can see the gap that is created when the inner edge of the derailleur stop comes into contact with the large radius hanger stop. That is way out of what Shimano, or Campy want to see. They both specify a 1mm radius at that point... Anyway, below is a closeup of the area... imagine that open angle extrapolated outwards and you can begin to appreciate that that derailleur is being stopped quite a bit before where it should be...
It only took an email to Pilo with pics similar to these for them to say... "Thanks for those pics and explanation, we will change the design". They did so, and were super pleasant about it. Wheels Manufacturing in the USA wasn't even making a hanger for the C59 at the time, which is why I sourced out Pilo in the first place. I should say right now, that the quality between Pilo and Wheels Manufacturing is the same, but I was super impressed that Pilo was so quick to recognize the need for the design change. Below is a closeup of the redesigned C59 hanger. They sent me a couple... (oh, and that's not a crack, but blown up like this it might appear that way, it's just a bit of grease that I didn't do a good job of cleaning off for the photo, it's actually never been installed; the grease was residual on the threads of the derailleur bolt)...
And one of both the before and after versions of the Pilo C59 hangers...
So, why did I show you that you might ask... well... because it's one of the things that is also clearly out of spec on @pdlpsher1's hanger from Paragon. Now, as I noted before, this may or may not affect a Shimano derailleur in the same way as it does Campy derailleurs simply because Shimano's derailleur tab stop is much thinner (at least it used to be) than Campy's. So, if the that's the case, that large inside radius may not even get touched. And you couldn't mount a campy derailleur to this anyway, as it would place campy's derailleur in a place it doesn't want to be. But it's something you should look for regardless of where you get your hangers from, especially if you run Campy.
Ok... so here's the DM hanger that @pdlpsher1 has on his bike...
Looking at it I can see at least two things that do not conform to Shimano's Direct Mount Road Hanger specification...
1) The inside radius of the "hook" as I just finished explaining is clearly much larger than the 1mm radius specificed. Does that affect Shimano's new derailleurs. Probably not, but I still need to check out the tab that butts up against it on a new Shimano derailleur. I will report back when I do. But it would certainly affect a Campy derailleur, which is a moot point when talking about the DM for sure, but in the event you're getting a replacement hanger, whether from Paragon, Wheels Mfg, Pilo, or somewhere else, this is something you should consider.
2) The flat edge (opposite the hook on the top side of the hanger) that provides a stop for the rear derailleur... it is absent on the Paragon DM hanger, albeit it is a mountain bike hanger, but I'm not certain that their road hanger is different in this regard... I suppose it could be... but in any case here once again is the spec for the road hanger. Note the flat edge I'm talking about...
So, when @pdlphsr1 pulls his road derailleur back, it's got no stop. It ends up looking like this... take note of where the edge of the derailleur hits the B-edge of the DM hanger on top...
Now let's look at what a BMC looks like when you pull the derailleur back as far as it can go. It has a properly designed and positioned Direct Mount hanger...
From the side... as far back as it can go... also look at how much lower it seems to be in relation to the wheel axle than @pdlpshr1's photo above. Although, I cannot tell if his bike is level or not, but judging by the bit of chainstay I can see... even if it's not quite level I suspect it's sitting a lot higher than the hanger on the BMC... Also note that the rear wheel is easy to remove in the pic below. It has good clearance up front.
And from the top... to show that it has stopped against the DM hanger...
But all this talk of hangers is just preamble for next post, because even if the hanger itself was designed exactly to Shimano's specs... it cannot be taken without considering how it mounts to the frame. The two are inextricably tied and you can't talk about one without knowing how it interfaces with the other. That's the subject of my next post to follow. But I need a bit of a break for now.