Shimano R9150 RD - Why so few direct mount hangers?

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

My pleasure!

Some builders prefer the axle to be more vertical. Knowing Carl, I'm sure he has a good reason for how he positioned the hood.

If a dropout is designed exclusively for DM, I think there is an opportunity to optimize the slots for both QR and TA to a true vertical position since the designer doesn't have to worry about the QR nut hitting a traditional style derailleur. The reality is that nobody is going to design a frame solely for Shimano DM. So the potential benefits of the derailleur "being out of the way" will never be realized.

I agree that far enough back is far enough back. Not much to be gained by being able to pull the derailleur any further back than necessary. In some ways, I find the positive stop actually helps get the wheel in faster (provided it doesn't hinder the wheel of course).

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Calnago
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by Calnago

Zanconato! Of course. I've seen your bikes, at least pictures of them. Very nice. Classy. I like that. Thanks for joining in the discussion and giving it a bit more credibility.
Image

I've got no issues with wanting to position the slot on the droput so that it's more vertical as that is yet another way to make rear wheel removal even easier. I start having some issues if it actually goes beyond that and the slot becomes, even slightly, rearward facing however. I think there could be some basic safety concerns, albeit unlikely, in that case. But where the ultimate position of the derailleur is tied to the rotational position of the dropout, as is the case here with this Paragon hanger and it's associated dropout, then I think some extra care needs to be taken to ensure that the derailleur ends up where it should be. Keep in mind that I'm not at all sure that @Pdlpsher1's hanger is definitively in the wrong place without being able to measure it myself, but from the pics it sure looks like it's suboptimal. I could see it being put back there if an older derailleur was being used trying to "make it work" with a large cassette at the expense of crisp shifting, but with the new Shimano Shadow derailleur, and the long GS cage to boot, I think the optimal position for premium shifting while being able to also access the large cogs is right where Shimano wants it to be and what they designed around. I dunno... I'm having difficulty seeing why anyone would put it anywhere else at the moment.
Last edited by Calnago on Thu Feb 01, 2018 2:25 am, edited 1 time in total.

by Weenie


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zank
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by zank

Thank you, sir! I'm a long time lurker/infrequent poster. I always learn a bunch here. Happy to participate if I feel like I can contribute in a meaningful way.

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Calnago
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by Calnago

zank wrote:
Thu Feb 01, 2018 1:47 am
...
If a dropout is designed exclusively for DM, I think there is an opportunity to optimize the slots for both QR and TA to a true vertical position since the designer doesn't have to worry about the QR nut hitting a traditional style derailleur. The reality is that nobody is going to design a frame solely for Shimano DM. So the potential benefits of the derailleur "being out of the way" will never be realized.

I agree that far enough back is far enough back. Not much to be gained by being able to pull the derailleur any further back than necessary. In some ways, I find the positive stop actually helps get the wheel in faster (provided it doesn't hinder the wheel of course).
One final thing regarding what you say about the potential benefits of the derailleur being "out of the way" never being realized.
Even if the frame manufacturers did in fact design frames solely for Shimano DM, the derailleur will still not be "out of the way". It will be right where it is, now... whether or not the DM hanger or regular hanger plus B-link is used. Like I've been trying to say... it's the design of the rear derailleur and it's wrapping ability that makes it both good from a performance point of view and maybe a little bit more frustrating because it in fact is "in the way" a bit more. But I can live with that. It's the upper pulley and cog interface that causes the kufuffle when removing the rear wheel. But I agree that to the extent a more vertical drop of the wheel becomes a reality, and the cogs can clear the upper pulley during that vertical drop, then there would be no issues caused by even the most minimal clearance in front of the rear tire and behind the BB, since the wheel wouldn't have to come forward even the slightest bit.

But But But.... I LIKE MY CAMPAGNOLO! Lol. Please don't make Campy (or SRAM) shift worse, or even unacceptably in the process by only supplying a hanger that works with Shimano optimally. Let Shimano take on that responsibility of designing a perfect direct mount hanger for every frame out there if they feel it's that necessary. They're big enough, They're rich enough... and doggonnit... I hate them. Ha... peace out!

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zank
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by zank

I understand what you mean. I was more referring to the idea of being able to bring slots or pockets closer to vertical and not having to worry as much about bridge placement. But yes, the derailleur itself is still sitting in the same place.

pdlpsher1
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by pdlpsher1

I went and measured the two distances using Calnago's method. I came up with 36mm (horizontal distance from the wheel axle) and 22mm (vertical distance from the wheel axle). If I get the road version of the DM hanger how would it change those measurements? Also, I have a very low BB by design (80mm BB drop). So this might make my RD look to be in a different position than if the bike had a normal 70mm BB drop.

As for my previous comment that DM hanger makes wheel removal easier, I stand by that comment. On my other bike the QR nut hits the part of the RD around the RD bolt preventing the wheel from dropping down. I can certainly force the wheel down however I don't like the idea of the QR nut scratching the RD. Hence I remove the QR nut completely before I remove the wheel. With the DM hanger the RD bolt has been moved rearward. The QR nut no longer will hit any part of the RD

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Calnago
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by Calnago

I don’t know how many times I have to say this, but your skewer nut jamming into the derailleur knuckle on the way out is a completely separate and independent issue form what we have been discussing. That’s a frame design issue. Your frame. Period.
As for your measurements thanks for doing that. It confirms what I think I’m seeing. It’s too far back and too high. The BB drop is taken into account already by the fact you’re using the center of it as a reference point for your straight line through the BB center and the rear axle. If your drop was 70mm it just changes the line but everything is relative. The specs indicate that clearly.
Bottom line...your derailleur is not very close to where Shimano wants it to be. The road hanger may help somewhat, for sure it will have a “hook” which is 10 degrees different than the mtn bike hanger and will bring it down and forward a bit. And when you say “vertical distance” from the axle it’s only “vertical” if your B.B. center and axle are level, which of course they aren’t if the bike is just sitting on the wheels on level ground. Because you use the word “vertical” I’m not sure you measured it correctly. The distance you need to be measuring is a perpendicular line to the straight edge created by the line through the BB center and the axle. That would not be a vertical line if the bike is sitting on its wheels on level ground. Make sense? Although, if you did measure it that way, then perhaps it’s closer than I initially thought and the numbers you stated err in the wrong way. Anyway, it’s up to you to figure out “why” your bike’s derailleur position is out of spec with Shimano, if it is. If you measured correctly and got those numbers you stated, then it is. And it may shift ok... you seem to think it’s flawless. So maybe you do nothing and just be happy with it. Nite.

pdlpsher1
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by pdlpsher1

A frame problem like this one? https://www.youtube.com/watch?v=FRX98HXQz10 The frame I have is a Fuji Transonic. I run a Conti 4k 25mm tire on the rear wheel (17C). I guess the wheel cannot move forward enough for the QR nut to clear the RD. So perhaps it's a similar problem as you have found on some frames with fat BBs that caused wheel removal headaches? In any case it's not a really big deal. I just remove the QR nut and the wheel falls out. I won't be riding the Fuji anymore.

I followed your instruction on the measurements. I just used the term 'vertical' because it's convenient. The measurements were done parallel and perpendicular to the imaginary line between the wheel axle and BB centerline.

When I get the road DM hanger I'll run the measurements again.

Zank- yes, my Ti frame is built by Carl Strong. I don't know how you knew but you have very sharp eyes. I love my bike, my first custom bike. I can see myself going for the custom route from now on.

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Calnago
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by Calnago

Yes, exactly like that. In the video link you provided the chainstay bridge is not allowing the wheel (with the 25mm) tires to come forward easily. Lynskeys suggestion to file the dropouts (assuming the lower forward portion) a bit probably wouldn’t have worked so well because the forward motion was being held up by the bridge and tire interference. A 23mm tire would be fine in that case. The guy just filed some of the derailleur washer off instead. So yes, this is not so rare but it needs to be taken into account by the frame builders. And clearance issues like these are much more likely to occur on road bikes with tight geometries than bikes with long chainstays and loads of clearance between the tire and BB.

It’s really the same thing that’s happening in some cases with the rear derailleur issue except the clearance issue comes between the sprockets and the upper pulley of the derailleur, when the tire gets squeezed as far forward as it can go. At this point, the wheel is already well out of the dropouts but then it’s squeezed by the pulley and the front of tire squeezed up against the inside of the BB shell, or a chainstay bridge. Same kind of thing, just different touch points. So, it’s a frustration more than anything that some people need to get used to and be aware of. I haven’t seen any situations where it’s been impossible to get the wheel out, but i could see it happening in rare cases where an extreme “perfect storm” occurs as I described earlier in the thread. And it’s clear what Team Sky did on Kwiatkowski’s bike to help in that regard. I did the same thing on one of the bikes I featured in some photos I showed. But that leaves a gap between the stop on the hanger and the derailleur stop and relies solely on the torque of the derailleur mounting bolt to keep everything in place. Shimano says that’s a NoNo. Oh well. It’s a trade off.
With your bike, we’re just trying to get the shifting as good as it can be at this point and you already think it’s very good. An adjustment to the B-screw improved it from where you started. I think for sure you will see an improvement with the road hanger, regardless of whether the dropouts are in the most optimal rotational orientation. How much or whether you will even notice I don’t know. But when you do get the road hanger maybe some pics of the “wrap” with the chain (double check to ensure it’s the right length when you put the new hanger on) in small ring/ biggest cog and small ring/ smallest cog would be good. If I get the chance to work on or build a bike with the new GS cage derailleur and a 34 tooth cassette I’ll be sure to do the same and post back here.
I don’t think there’s anything more to discuss here. A lot has been covered pretty well. You don’t get this on Instagram :).

beanbiken
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by beanbiken

Just thinking here, one could deflate the tire to allow more space to shift the wheel forward....... rather than modifying components or altering geometry...... just a thought

BB
Ahhh, coffee & carbon

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Calnago
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by Calnago

Yup, and that will usually give enough space to get it out. But that would turn a minor “annoyance” into a major pain in the ass. It’d be pretty funny watching the guys doing a wheelswap in the TDF, first deflating the tire to get it out, then deflating the replacement wheel to get it in, then pumping it up again once it’s back in. Ha.
But you’re right... after 10 pages of theoretical nonsense and hand waving and false “Eureka” moments, deflating the tire will work too, if the removal issue is your only concern. We’re now kind of discussing some finer points of frame/dropout design to make sure the benefits of the “wrap” technology are being utilized, which is probably more relevant to the OP’s original question about “why aren’t more frame manufacturers jumping onto Shimano’s Direct Mount Hanger” bandwagon.

pdlpsher1
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by pdlpsher1

Being able to pivot the RD back to allow the wheel to drop out is not what I would call a false "Eureka" moment. This is required on a Shadow RD to aid wheel removal. You don't need to do this on a regular RD but one must do this on a shadow RD or otherwise the cassette will get caught up with the RD's upper pulley. For those people who don't have a tight frame problem hindering wheel removal the pivot trick will make wheel removal a trivial task.

Here's a pic I posted earlier on a bike with a normal dropout and a B link. Using this technique makes wheel removal a non-issue for 99% of the bikes out there. If a bike's frame geometry is truly so tight that even this method won't work, then Zank's idea of grinding down the B link is perhaps the best solution, until Shimano decides to modify the B link. All it needs is a very minor modification on the B link to allow more pivot in the RD.

Image

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Calnago
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by Calnago

The “pivot trick”. Ha... that’s just what has to happen normally when you remove a wheel with the new derailleur. I think it was just that when you actually posted a pic of it many thought (myself included)... holy crap... does it really contort like that. And so I couldn’t wait to go try it and sure enough, it does. But it was always doing that from day 1, I had just never really paid attention to it. So, if your wheel comes out easily when you pull the derailleur back like that (normal when removing the wheel) then you simply don’t even have the issue in the first place and the extra bit of hassle you may experience is simply due to the wrapping of the new derailleur and its more forward position than previous generations.
But like both Zanc and I are saying, once you’ve pulled it back far enough to clear the pulley, pulling it back even further does not make it easier... rather it just starts confounding things with the lower part of the chain. It’s a balancing act at that point. Probably the best solution for just achieving those few mm of extra clearance if needed is to just alter the b-link angle a tad so that it points as straight back as possible and make sure it’s torqued down enough to prevent slipping since it’s no longer using the stop for any support.

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wheelbuilder
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by wheelbuilder

Oh my goodness pdlpshr just let it go! You did not invent the pivot trick. This is done on every rear wheel removal of every bike with a rear derailleur (regardless of brand or model) since the beginning of time! It is part of the mechanics and muscle memory of removing a rear wheel. The reason a few of us had that "false eureka" moment after you posted that photo, is because none of us (or I haven't to speak for myself) had the opportunity to view a photo of the procedure from the side. Something about your photo to me looked like you had discovered some way to force the derailleur to rotate backwards even farther than what everyone else had already been doing. When I was able to do it in person, nothing had changed. Same position. Same interference between cogs and upper pulley. I take exception to you stating that this is not an issue on 99.9% of bikes out there. Most members participating in this thread have two or three bikes at most at their disposal to gain their experience from and MOST of those members have not experienced an issue. I work at a road shop and am telling you or anyone else that will listen that there is a number of bikes out there in certain sizes where this can be troublesome. I made a huge mistake earlier in this thread by using the term "impossible" Everyone jumped on that and set out to solve my problem for me. It was an exaggeration. I mentioned three particular bikes in which it presents a problem. That is more real experience than anyone else here has offered. Calnago has apparently found a photo of a mod that SKY is making on the same bike that I mentioned three pages back.
You can continue to try and convince me that I have not experienced what I experienced all you want. Until you work on road bikes all day long, I'm not going to accept your findings.

by Weenie


XCProMD
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by XCProMD

zank wrote:The reality is that nobody is going to design a frame solely for Shimano DM.
But this is the only reason Shimano has created this new standard. The others are able to give good chain wrap up to 32T with traditional hangers and no wheel removal issues Shimano could have done it too.

They already tried this with MTB’s, but the timing was wrong as SRAM came with real improvements (XX first, XX1 later) that gave them again a good slice of the OEM cake. Look how many MTB’s have DM dropouts these days. Fortunately for everyone but Shimano they failed.

Before eTap they were at an extremely high share of the road OEM market. So they tried it here. Fortunately for us, eTap will save us this time around. At least I hope so.

They tried it when we went all in with discs in MTB’s. They thought selling Dual Controls would make everyone spec only their complete groupsets. Fortunately they failed at that too.

Everybody in cries about how little money the cycling industry makes even when bikes are more expensive than ever adjusted to inflation. This is an inefficient business that remind as much of socialism in some aspects. But we fed this big behemoth since the late 70’s so it’s only our fault.






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