Shimano R9150 RD - Why so few direct mount hangers?

Discuss light weight issues concerning road bikes & parts.
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wheelbuilder
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by wheelbuilder

Great conclusion Cal. So meticulously thought out and equally written. Well done. I feel a bit pardoned for having some real frustrating moments with this system over the last year and a half. Most people will never have to deal with the wheel removal difficulties and can enjoy the awesome shifting and positive wrap that 9100 affords.


pdlpsher1
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by pdlpsher1

I just read this and I’m a bit curious if my bike’s dropouts are rotated in the correct position. So I went to the garage and took some pics. The bike is perfectly level. I have a very low BB hence the angle of the chainstays look odd. I removed the QR nut so you can see the dropout slot. I can see what you mean by the rotated dropout affecting the position of the RD. I don’t know how my frame builder accounted for this. The weld does appear to be perfectly centered on the dropout ‘hood’. I’m curious on how frame builders align the rotation of the dropouts. It’s possible that my RD position is not where it should be. However due to the forgiving nature of Di2 I have sublime shifting in the current configuration. In any case there’s not much I can do except wait for the road version of the DM hanger. The research by Cal is interesting and much appreciated.

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Klaster1
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by Klaster1

I'd like to thank @Calnago (and everyone else) for such a detailed discussion, it provided a lot of insight useful for one of my winter projects (a custom DM hanger).

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Calnago
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by Calnago

Thanks @Klaster1, and others who expressed appreciation.

Also, @pdlphsr1... it would be fairly easy to ascertain whether or not your hanger is in the right place or not, and if not, just how far it is out (if it is). The thing is, with your dropout design, it is fairly easy for the frame builder to rotate the dropout (within limits) to accommodate different angles seatstay and chainstay junctions, however... you can't ignore how this is going to affect the ultimate placement of the derailleur. Framebuilders have all kinds of jigs etc to keep things where they want while welding/brazing etc. But it's up to the framebuilder to make sure that the derailleur will end up where it needs to be. If you find out that the derailleur is in fact not where Shimano wants it to be according to their spec, then I'd want to know why the builder departed from that spec. A perfectly valid question for sure.

Oh, and I'm not sure what you mean by the "forgiving nature of Di2". It is anything but forgiving, in fact it is very precise and forceful. You touch a button, and it moves a precise amount, the same way, with the same force, every time. And if you're not ready to shift, like barely pedaling when you hit a hill and hit the button to move to the big ring from the small, it doesn't know anything about the terrain you're about to encounter, or that maybe you are making a bad shifting decision, or that maybe your cadence is a bit slow at the time of shift. It is just going to try and jam that chain onto the big ring regardless, and there's no back tracking once you hit that button until the action is done, or at least attempted. I cringe at the thought of the bad shifts that must occur in the hands of the inexperienced and the mechanical stress it can put on the drive train.

Looking forward to seeing what you find out about your frame and the hanger placement, whether the road hanger makes things right, and getting things adjusted as well as possible.
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pdlpsher1
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by pdlpsher1

The frame builder would have some control but as you can see from the second pic there's not much room on the 'hood' of the dropout below the chainstays. Paragon had placed the 'hood' where they placed it to allow the hanger to be positioned correctly. So Paragon has a big role in this. My builder simply put the seat and chain stays in the center of the 'hood'. I think perhaps I should direct the question to Paragon since they designed both the dropout and the hanger.

I must stress that I'm a long time Di2 user and my current setup gives me sublime shifting performance. And I also like the Paragon DM hanger since I can pivot back the RD without much restriction, and others will benefit from the design to help wheel removal.

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Calnago
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by Calnago

My, my, what am I going to do with you. Most dropouts will state a certain "degree", indicating the angle that the dropout ends line up with the stays. There is less leeway on those dropouts to stray from that. The type of dropouts on your bike allow a relatively lot of leeway as to their positioning (that's what I was referring to earlier), but only one spot that the hanger can fit in. To me, if that pic you show without the skewer nut in it is with the bike on level ground, then the dropout looks like it is rotated too far clockwise. Why do I say that? Because it looks like the wheel would actually move rearwards as it slides out of the dropout. Hmmm... I don't know any dropout that allows a rearward facing slot, aside from Track bikes. Paragon has no control over where the frame builder attaches the tubes to the surface of the dropout. They've just designed a dropout that allows for some flexibility in that regard. If your builder just "simply put the stays in the center of the hood" without regard for where the cutout for the hanger is located, well then...

As for you thinking that being able to pivot the rear derailleur back that far makes for "easier" wheel removal, uh... never mind.

Good luck.
Last edited by Calnago on Wed Jan 31, 2018 1:08 am, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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beanbiken
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by beanbiken

I will also chime in with my thanks and appreciation to Cal. This has been an very informative thread to follow. My rear wheel is still "tight" but not a problem with removal/refitting, just need to be careful. Altering the rear of the B link did make a slight difference and alleviated my problem

BB
Ahhh, coffee & carbon

pdlpsher1
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by pdlpsher1

I still don’t quite follow on the dropout position. If the builder rotates the dropout counter-clockwise, there no hood area for the chainstays to attach to. The hood part of the dropout has to be positioned correctly. So the dropout design (Paragon in this case) comes into play. The dropout I chose is a small one. Paragon also makes a much larger dropout which has probably more flexibility on chainstay and seatstay placement.

The road DM hanger will also change the position of the RD. At this point I have no issues with the bike so I might just keep everything as is. As I have stated earlier I think the new Shadow RD is awesome, with or without a DM hanger.


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beanbiken
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by beanbiken

pdlpsher1 wrote:
Wed Jan 31, 2018 3:35 am
At this point I have no issues with the bike so I might just keep everything as is.
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Sounds like a great idea...........

BB
Ahhh, coffee & carbon

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zank
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by zank

Hi Calnago,
Have you considered grinding the square corner off the b-knuckle to allow the RD to pivot back further?
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You can see with the paragon DM hanger that you can pivot the hanger further back compared to the stock b knuckle.

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You can see where that square corner on the b knuckle makes contact with the derailler body limiting the movement.

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Just an idea.

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zank
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by zank

Just did a quick grind and it got me maybe 10 degrees or so. It might be enough for the cog to clear the pulley when you are trying to drop the wheel out. You can probably get more movement with a better job grinding.

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Calnago
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by Calnago

Oh no... yes, I’m aware that would happen if you grind away that edge, but it’s there for a reason. I certainly don’t want everybody to start grinding away on that B-link. It was just something I was pointing out on the Paragon hanger that departed from Shimano’s spec. I’m mostly interested in why @pdlpsher1’s hanger does not “seem” to be even close to where Shimano wants it, but the wheel removal issue only affects a small number of bikes.
@Zank... did you grind that off just as an experiment or were you having difficulties with wheel removal as well. The thing is, with the new design, it WILL be a little more of a hassle to remove any wheel, but the benefit of having a really good “wrap” around the cogs outweighs that. With @pdlpsher1’s situation, he doesn’t seem to be getting any of that benefit but I think that may be just how it is given how the frame and its interface with the dropouts turned out.

But good work @zank for demonstrating that. Still, Shimano clearly doesn’t want the derailleur to be able to extend past that stop. I’m not sure exactly why yet, but my guess at this point might be to prevent using the derailleur on super large cassettes that it just isn’t designed for, like a 40 or something. Ha, where will the madness stop. Image
The “mountainization” of the road bike continues, and I don’t like it. :)
Last edited by Calnago on Thu Feb 01, 2018 1:13 am, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
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zank
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by zank

I figured you had explored that idea, but wanted to throw it out there just in case. It may also help some people get a clearer picture of why it's happening.

No, I sacrificed this one because that derailleur is going on a DM hanger and I have a drawer full of mtb and road b-links at this point.

I understand your point about the Paragon hanger being out of spec in regard to not having that positive stop. And I'm wondering if it's there simply to prevent the barrel adjuster from hitting the hanger as in my picture above.

I totally agree the added chain wrap is a plus, just like on the mtb side. We do have a bit of latitude on how we rotate those dropout hoods. I tend to go a little more towards more chain wrap, but I also build few bikes with chainstays under 410 mm and I am hyper aware of my chainstay bridge placement. But the difficulties you are running into make complete sense to me. Tight spaces everywhere these days.

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Calnago
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by Calnago

Thanks Zank! Now that I'm at my real computer for a few minutes, I can better see the pics you posted. Yes, they absolutely do provide more insight to those that are still trying to figure out exactly what the hell these guys are even talking about. Thanks for the B-link sacrifice as well... all in the name of better understanding.
Zanc... you're obviously a frame builder, and apologies if I should know you. I've dabbled in frame building a bit years ago, when carbon was just becoming all the rage. I almost bought my own milling machine. But instead got a Colnago C40. However, I really appreciate the artisan work that can be shown off with a steel frame. Keepin' it real!

The thing with @Pdlpsher1's bike is that he's got long chainstays at 425mm he says. So unless the bridge up front between chainstays is preventing it, I don't see why the dropouts weren't situated such that the end result of the hanger would at least allow the chain wrap that the derailleur was designed to get in the first place. I don't think it's just because of the large 34 tooth cassette, and in any case, the GS cage on the derailleur should allow for that.

And oh yeah... @Pdlpsher keeps going on about how even if your bike does not have a wheel removal issue, that being able to yank the derailleur all the way back like that will make rear wheel removal even easier. I completely disagree with that. Once you clear the upper pulley from the cogs, then pulling the derailleur even further back will not make it easier to get the wheel the rest of the way out. In fact, pulling it back even further is just going to pull on the chain below the lower pulley and just add to the frustration. You want to be able to pull the derailleur back just far enough for the cogs to clear the upper pulley, but beyond that you're just making it more difficult again.
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Calnago
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by Calnago

@Pdlphser1: It's pretty easy to just check where in space your hanger sits in relation to Shimano's specs. Here's how, if you're interested, and I would be if I were you.

1) First, get a straight edge and place it so that the bottom edge intersects both the center of the bottom bracket and the center of your real axle (the skewer end).
2) Take a little plastic triangle from your kid's geometry set or you can get one at any drug store or school supply store for a couple of bucks and orient them like in the picture below...
Image

Now, line up the plastic triangle thing so that it is a) square to your straight edge and b) intersects both the rear axle center (skewer), and the center of the pivot where your derailleur attaches to your DM hanger... like in the pics below. From that you should be able to read that distance... which in the case below... is ~32mm. And what is the distance according to the Shimano spec again?... surprise surprise... 32.65mm. Imagine that. I'm gonna call this one good. And then the vertical distance below the axle should be 34.39mm. In my pic below that number is slightly more than that after converting the inches scale to metric, but it's kind of a crude setup to begin with while we're just placing that straight edge "about" in the middle of the BB center and the axle. Point is, if we're this close with such a crude measurement, I'm thinking we're probably good overall as far as where the derailleur is in space at least. There's still the difference in hook angle of 10 degrees between the mtn and road hangers, which would only make the road shifting a little more sluggish by setting the derailleur back even a little bit more.
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We've kind of taking a few turns and twists in this thread, but let me reiterate the primary reason why I decided to jump in in the first place. It was because I'm getting tired of people who have no clue continuing to say that the DM hanger makes rear wheel removal so much easier. It simply does not. The derailleur's location is, or at least it should be, the same whether you use a DM hanger or a regular hanger with the supplied B-Link. And neither of those hangers are interfering with rear wheel removal but rather, it is the design of the derailleur itself which may, on occasion, make removing the rear wheel a little bit more frustrating. And in the extreme rare cases, a lot more frustrating. Where the wheel gets hung up in those cases is in the cogs and the upper pulley, but if you can get past that, it's all good. The added chain wrap just adds to the crispness of the shift and to the extent it's wrapping more teeth, less wear on your cassette. In a nutshell, it's good. We like it.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ


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