New groupset day! R8000 rear derailleur mounting

Discuss light weight issues concerning road bikes & parts.
Bergwerk
Posts: 12
Joined: Mon Dec 19, 2016 10:06 am

by Bergwerk

Fitted my brand spanking new Shimano Ultegra R8000 Groupset today. :beerchug:

The rear derailleur arm seems perilously close to the spokes though when in the big ring. The limit is set correctly, if i take it in any further it shifts down a cog. Is this narrow margin normal? Seems like it would go into the weel with the slightest nudge... :shock:

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by Weenie


TurboKoo
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by TurboKoo

I think your hanger is bent. You also have way too long housing at the final. Are you using OT-RS900?
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Bergwerk
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Joined: Mon Dec 19, 2016 10:06 am

by Bergwerk

The hanger is brand new. Unlikely that it's bent. You're right about the housing, gonna shorten that up.

Anyone have the same derailleur? How much gap is there beteween the arm and the spokes when in the big ring?

Here's a pic from bikeradar I found. Also seems it's going to go up pretty close.
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siauragama
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by siauragama

Image

Short cage though.


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Bergwerk
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Joined: Mon Dec 19, 2016 10:06 am

by Bergwerk

Thanks for sharing that picture.

Just measured mine. The gap at the bottom is about 8 mm. At the top only 3mm though. Seems a bit close for comfort, but maybe I'm overthinking this..?
Image
Image

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siauragama
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by siauragama

Bergwerk wrote:
Mon Apr 02, 2018 8:56 pm
Just measured mine. The gap at the bottom is about 8 mm. At the top only 3mm though. Seems a bit close for comfort, but maybe I'm overthinking this..?
I'm with TurboKoo - I'd check the hanger. Maybe it's just photo angle, but your cage seems to be almost parallel to the spokes. Hanger could be out of alignment even if it's a new frame/hanger.

:beerchug:

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ms6073
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by ms6073

While this won't solve the question about the bent hangar, it sure looks to me as if the chain is too short when compared with the image below:
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wingguy
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by wingguy

Bergwerk wrote:
Mon Apr 02, 2018 7:52 pm
The hanger is brand new. Unlikely that it's bent.
Lol, no, sorry. One of the first things any decent mechanic would do building a new bike is to put an alignment tool on the hanger. They come bent all the time. You do not want to take it on faith that it's straight.
You're right about the housing, gonna shorten that up.
Make sure it's the OT-RS900;

Measure this;
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Find length here;
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If I remember right from doing my R-series it's the shortest possible distance, so 110mm. It seems crazy short compared to normal mechs and cable, but it is right.

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Calnago
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by Calnago

One of the things you always should do, especially with brand new bikes, is to check and align the hanger.
Also, how much space between your derailleur cage and the spokes will depend on a couple things...
1) the rim depth: a low profile rim will likely have the spokes ending up a little closer to the cage than a high profile deep rim. Simply because of the angle the spokes have to take from the hub flange to the rim.
2) how flexy the wheel is... this does not affect the distance when in the stand but when you are in your lowest climbing gear going up a steep incline, sometimes you might hear a slight pinging as the spokes graze your derailleur cage. If that’s the case make sure your limit screw is adjusted correctly and err on the side of keeping it further away if possible.
A couple of millimeters clearance is good, but I’ve run even less (maybe a millimeter) with a stiff wheel. Again, it depends on a few things... if your hanger is made of soft cheese (and some are) the chances of “overshifting” are higher as well. So... all things to be aware of.

The final thing has to do with the rear derailleur housing you’re using. Is it the housing that came separately in the box with the derailleur? Make sure you use that versus the piece that comes in the cable kits. Very different cables, the one in the box being wound like a brake housing cable and much more flexible than your standard derailleur housing. And as was said, check the length, adjust it so it’s fine at both small/small and large/large combinations. It has no effect on how close your cage is to the spokes, but it does affect how easy it is to pull the derailleur back and out of the way as you remove your rear wheel.
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kode54
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by kode54

i've seen a few Cervelo's that had misaligned hangers right out of the box.

i always check with a alignment tool to make sure or straighten it out.
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Bergwerk
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Joined: Mon Dec 19, 2016 10:06 am

by Bergwerk

Wow. Lot's of great info, thanks for posting all!

So I'm going to get the hanger checked out, or see if I can get my hands on an alignment tool. I think It's mainly the picture though, the measurements show it's not parralel tot the spokes by a long shot. But better be sure as you say.

I didnt know the cable housing on these was a bit of custom tubing. Will replace that with the original.

GothicCastle
Posts: 134
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

Bergwerk wrote:
Mon Apr 02, 2018 7:52 pm
The hanger is brand new. Unlikely that it's bent.
Ha. Ha ha.

New hangers often need alignment. Definitely start there.

g00se
Posts: 32
Joined: Fri Feb 21, 2014 11:22 pm

by g00se

A tip if you dont have a hanger tool - but do have an old QR rear wheel knocking about:


https://www.youtube.com/watch?v=TnwreRrorIA

BUT DOUBLE CHECK THE THREADS FIRST.

ooo
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by ooo

--(deleted, alreday suggested)--
'

Bergwerk
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Joined: Mon Dec 19, 2016 10:06 am

by Bergwerk

GothicCastle wrote:
Tue Apr 03, 2018 6:17 am
Bergwerk wrote:
Mon Apr 02, 2018 7:52 pm
The hanger is brand new. Unlikely that it's bent.
Ha. Ha ha.
New hangers often need alignment. Definitely start there.
Assumption is the mother of all f# ups. Thanks for the contructive riducule.
g00se wrote:
Tue Apr 03, 2018 8:46 am
A tip if you dont have a hanger tool - but do have an old QR rear wheel knocking about:

https://www.youtube.com/watch?v=TnwreRrorIA

BUT DOUBLE CHECK THE THREADS FIRST.
Ok. :shock: Definately not trying that with my nice frame.

by Weenie


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