V20 RD Hanger angle

[vosadrian]

Hi All,

I have recently fitted my V20 with an Shimano Ultegra R8050 (DI2) rear derailleur. It is optionally a direct mount RD so has an extra attachment point and the pivot on the RD is not at the hanger like older RDs. If I just mounted it as you would expect with the RD sitting against the notch on the hanger, I had all sorts of issues with a loose chain on the small ring on the front and the top half of the cassette. I tried everything with the B screw adjustment, but it turned out the problem was that the RD was just rotated in the wrong position. So I loosened the mount and rotated it so it was no longer against the notch, and this seemed to fix all my issues.

I can run with this for the time being, but not sure if it will move over time with riding as it has no location notch. Also, every time I loosen the RD I will have to find the perfect position again.

So has anyone else run into a similar issue? Is there a different RD hanger for the V20 that positions the RD better? Or has someone modified the one I have in some way to provide a better solution?

Cheers,

Adrian

 

[jond]

That sounds wrong vossi. Is the drop out bent or can be reversed.? Maybe upload a picture. Not seen the rear mech before so.....maybe that fit direct mount to frame is not an option after all for frames with a drop out hanger.

just had a look online shimano site. Says a “without bracket spec available”

is it removable?

 

[vosadrian]

I believe all new (the last couple of years) shimano road rear derailleurs are direct mount compatible and they come with a bracket that converts any old style RD hanger mount to direct mount already attached to the RD. So to use a direct mount hanger, you remove the bracket, but the V20 is not direct mount so you need to leave it on. Here is a photo of the problem (the black bracket that bolts to the hanger is the direct mount adapter bracket mentioned above that comes with the RD). This is with small ring and 3rd smallest cassette (since DI2 will not allow cross chaining to smallest on this RD):



See how the chain is sagging it is so loose. The next photo is exactly the same, but back pedalling the crank about quarter of a turn:



See how the top of the chain is now derailed and so loose it sags to nothing (falling below the chain stay!). It was completely unridable like this as it was so loose on anything smaller than the 3rd biggest cassette on small ring, it was just flapping about and fell of if you back pedalled. I did try adjusting the B screw, and it did improve, but not enough. Also, the tight B screw causes shifting issues (the shift does not happen on some gears and it just makes lots of noise).

Note that this is with the black bracket attached where it locates correctly (the bracket has a notch to mate up to the notch on the hanger that the B screw normally pushs against). This is the way that the Shimano docs say to do it. Notice the black bracket makes an angle of about 135 degrees with the hanger. I have now rotated black bracket back so the angle is closer to 90 degrees. The bolt is as tight as I am confident to run it, and I hope the bracket will not rotate, as there is nothing locating it to stop it except the clamping force of the bolt. This solves all my issues. The RD has more tension on the spring so the chain is tight even in small/small combo. I can adjust the B screw to get the right clearance from the jockey wheel to the cassette, and gear changes are nice and crisp.

So it seems to me that there is something about the V20 hanger that is optimised for the SRAM setup and does not work well with the later Shimino RDs. I was just wondering if there is some way to rectify this so I am not relying on the clamp force to hold the RD at the right angle.

 

[Don1]

How about something like a wolftooth extension?

 

[vosadrian]

Wolftooth DM may help, but will probably have the same issue where becaused of the V20 hanger it won't naturally sit at the correct angle. If there was a similar thing with a screw adjustment built in so you can customise the angle (similar to the B screw on a standard mount RD), that would be great and should solve the issue by providing a stop so the mount cannot move.

 

[jond]

Are you able to remove any more chain links without compromising the efficacy of big ring

what does it look like big big . Can you try remove the direct mount bracket at all ?

 

[vosadrian]

I simulated a shorter chain and could only remove one link pair before big-big won't work, and that does not solve the issue on small-small which is still way too loose

It seems that all new (last few years) Shimano road RDs are direct mount compatible. If you have a bike without a direct mount hanger, you need to keep the black bracket in my photos in place or buy an aftermarket eqivalent. You can't run without the bracket on an old style standard mount hanger as the new RDs are meant to have the pivot moved further down/back to work correctly. And it does appear that the position and rotation of the RD mount is a bit of a thing. I found this thread on weight weenies that goes into it a bit:

https://weightweenies.starbike.com/forum/viewtopic.php?t=149460&start=60

That one started because some people were unable to remove the rear wheel because the RD was in the way. The correct position is further back and with more CW rotation than my photos above. It seems that Shimano have made some assumptions and Cruzbike did also, and that combined gives a bad RD position unless you rotate the bracket on the hanger and clamp it in position. All it needs to be right is to rotate it back so there is about 5mm gap between the stop on the hanger and the stop on the bracket rather than touching. I might glues something onto the hanger to extend the stop, but it would be great if there was an alternative hanger available that solced the issue. Is the V20 hanger specific to Cruzbike or is something similar used in other applications also?

 

[Don1]

I maybe in the same situation since I have a rd7000 series to go on. If I come up with something easy or have to make a different hanger I guess I'll make 2.

 

[vosadrian]

That would be great if you have the capability Don! Happy to pay you for your trouble.

 

[Don1]

It's amazing what a file, welder and a drill tap can do. I have tomorrow off so......

 

[vosadrian]

You need to fill the gap... but you need to work out what the gap should be first. You could either modify the direct mount adapter on the RD, or the hanger. Of course if you tighten in the right position and it does not move, you don;t need to modify anything... but you will have to find a way to align it if you have to pull it off and put it back on. I actually think a small screw pu on the hanger that can adjust in and out to adjust position could work.

It would be interesting to see if you run into the same issue as me just running it as is. I did notice that the shimano specs for MTB and road hangers are different. Is it possible the V20 is using the same hanger as other cruzbike models that had a MTB groupset, and that is why?

 

[Don1]

Dunno. It's dark. The verandah where the bike is has spiders.. better not risk it

 

[jond]

I’ve run both road and mtb rear mechs on vendetta. Sram xo long cage 10 speed and ultegra 6800 11 speed. The drop out is frame specific. To my knowledge but I’ve not seen latest framesets. V20 2016 and V2 2014 same style dropouts with v20 better press fit into frame.

Perhaps try contacting shimano and @Robert Holler see if there’s been a work around possible alternative in development or available now.
Seemingly with this new ahem standard something has to give. Is this new design related to through axle frame development. Good grief .

drilling and tapping a dropout seems fraught with potential problems . Perhaps jb weld a block spacer for now as you suggested.

otherwise first flat in the dark will be the nightmare

 

[vosadrian]

It will only effect if you have to actually loosen the bolt holding the RD onto the hanger... so removing a wheel for a flat should not be an issue unless you bump it out of position. It will be an issue if you work on the bike and have to loosen the RD for some reason, as you will need to fiddle the position back to close to where it was and then adjust the B-screw. It would also be an issue if it was bumped out of position. It does seem the RD is less likely to be bumped on a V20 than a DF though.

I did first ride yesterday, and it seemed to hold position OK.... so fingers crossed!

 

[jond]

It will only effect if you have to actually loosen the bolt holding the RD onto the hanger... so removing a wheel for a flat should not be an issue unless you bump it out of position. It will be an issue if you work on the bike and have to loosen the RD for some reason, as you will need to fiddle the position back to close to where it was and then adjust the B-screw. It would also be an issue if it was bumped out of position. It does seem the RD is less likely to be bumped on a V20 than a DF though.

I did first ride yesterday, and it seemed to hold position OK.... so fingers crossed!

fingers crossed double.

I read the weight weenie post. Very illuminating thanks. Good grief I’m holding on to my 10 speeds and hold special the 9 speed . It’s now up there with quick release skewers.

8 nm holding the b link in place.....bump. At least the pressfit of the existing dropout is tight. Yeah less likely on the vendetta. But you’ll be flat repairing with bike upside down pointed up hill to protect the rear mech.

wrapping the chain partially around the cluster used to be simple. Shift performance now may be improved with this newish shimano standard shadow road but for a minority of frames it’s seemingly problematic.

We seem to be talking about two different styles of dropout necessary depending upon group selection.

 

[vosadrian]

For me I did not like SRAM that the bike came with. I had leftover bits for a DI2 groupset. just needed the FD and RD. I have older stuff on my old bike (6870) and it works great. Would have been happy with that, but it is near impossible to get even second hand. SO just bought new RD and FD... and then the issues start. I think it will be fine but was not expecting this issue. The rest of it is really clean and neat. DI2 wires are mostly internal. I went with external battery and have a spare battery in my moose pack so I go flat I am covered. Battery is mounted under boom just in front of bars... so easy to access and out of wind. Should be more aero with the shift cables no longer there.

 

[Don1]

my temporary solution... rotate the RD to approximately where it should be and tighten the mount bolt. doesn't move. I will prolly get some generic hangers and have a play (a piece that sits between cruzbike hanger and direct mount bolt) but in the meantime I have a cruzbike I haven't ridden yet.......

 

[vosadrian]

So you ran into the same issue Don?

Same solution as me for the time being. Hopefully we can work out something more permanent. Surprised this has not come up on the forums before now. These new RDs have been about for a few years now.

 

[Don1]

i think SRAM is more in the DNA of cruzbike. the new shimano shadow deraileurs are different to the previous 5800/6800/9100 stuff but I think a different adapter (cruzbike hanger to direct mount) will do the trick. My welding of alloy is still a bit shameful but paint it black.....

 

[vosadrian]

Also, the specs for MTB and road bike (shimano) are different, so I wonder if the Cruzbike has some history with MTB groupsets and V2o kind of inheritted that.