Ultegra RD-8050 convert SS to GS

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zvucetic
Posts: 14
Joined: Tue Jan 08, 2019 8:23 am

by zvucetic

Hi,

I'm just checkin the option to convert di2 short cage to medium.

I was checking difference in parts for the two derailleurs:
http://www.sjscycles.com/Drawings/Shima ... ch_Doc.pdf
http://www.sjscycles.com/Drawings/Shima ... ch_Doc.pdf

Seems that the only difference is in the two plates (inner/outer).

Has anyone tried this, what are your experiences?

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Klaster_1
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Location: Russia

by Klaster_1

What's your goal? Do you plan to go 1x or use existing RD with wide range cassette? As far as I know, SS and GS have varying main parallelogram geometry to accommodate ramp angle difference between tight and wide range cassettes. Cage length only affects chain capacity. When you compare outer plates from diagrams, the cage rotation limit pin (beneath cage pivot axle) locations don't match, this might be an issue.

by Weenie


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zvucetic
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Joined: Tue Jan 08, 2019 8:23 am

by zvucetic

My goal is to mount the 11-34 cassete in case of hilly routes (or at least 11-32)
Are the ramp angles quite different in this 11-34 case?

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zvucetic
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Joined: Tue Jan 08, 2019 8:23 am

by zvucetic

alfus1 wrote:
Mon Jan 14, 2019 4:40 pm
Short cage 8050 doesen't exist, only medium (RD-R8050-SS) and long (RD-R8050-GS).

You only need Y3HR00040 and Y3HR98060 references.
so it's only up to chain capacity for the bigger cassete?

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Klaster_1
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by Klaster_1

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Last edited by Klaster_1 on Tue Jan 15, 2019 8:24 am, edited 1 time in total.

2lo8
Posts: 539
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

I'm pretty sure the parallelogram geometry is different between SS and GS because shadow RDs are only single pivot. Changing the cage will increase chain wrap capacity, but the slope of the slant is meant to track narrow range cassettes instead of wide.
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alcatraz
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by alcatraz

Short answer: You can't clear larger cogs by swapping the cage.

You can only increase chain wrap capacity.

If you only need a little bit more chain wrap capacity you can oversize pulley wheels. You can get a roadlink to clear big cogs but you'll sacrifice shift quality unless you run something like a 14-34t cassette.

If shift quality is important then use the appropriate size derailleur. If you don't use the cassette often just hunt for a 2nd hand ultegra 6800 derailleur. They aren't as expensive.

ooo
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Joined: Sat May 21, 2016 12:59 pm

by ooo

Shimano do not have "medium" cage in catalog, actual abbreviations meaning:
. . . . . short cage = . SS
. . . . .. long cage = . GS
super long cage = SGS

This will explain why changing cage will not improve shifting on cassettes that was not recomended for rd with stock cage:
Difference of GS and SS road RD (example: RD-6870 GS vs SS, photo by handsonbike):
Image
'

2lo8
Posts: 539
Joined: Thu Mar 31, 2016 10:32 am

by 2lo8

Shimano doesn't use short/medium/long cage consistently in their English language materials. They have called GS derailers short (when only GS/SGS), medium (and mid) and long (traditional catalog and tech doc usage) in various official Shimano materials. There's very little point bickering about the "right" way of calling a long/mid cage RD when it is obvious what is meant is GS because Shimano themselves are very bad at it, although I beleive that Shimano is trying to move from short/long/superlong to short/medium(mid)/long for "vernacular" and marketing usage.

The only thing shimano can seem to agree on is SS is not midcage, even though some people want to call it that since it can handle bigger cassettes than it used to.

All from the Shimano website:
RD-M9100-GS
- Short cage derailleur
- 45T max cog size
- Works with both 11-speed and 12-speed 10-45-tooth cassettes
- Better ground clearance (28mm shorter cage)
The medium cage 11-speed rear derailleurs (RD-M7000-11-GS)
The XTR RD-M9000 is available in GS (mid cage)
ULTEGRA Rear Derailleur (11-speed). RD-6800 (SS/GS) Short Cage/Long Cage
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kofsw4
Posts: 43
Joined: Wed Sep 20, 2017 10:28 pm

by kofsw4

I looked into swapping just the cage on my 6870 RD to be able to use larger cogs a while ago. In the end I got a good deal on a new GS derailleur and sold my old one on eBay. Cost me £30 and probably saved a lot of hassle, poor shifting etc

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zvucetic
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by zvucetic

seems that it's not only the plates

Image

But if the SS goes up to 11-30, 11-32 should fit with the b screw all the way?

alcatraz
Posts: 2214
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

The derailleur's "swing" angle is fixed, and it's different for each version.

The b-screw can help you to clear the cassette but it won't change the angle.

The manufacturer can specify a range like 23-30t support but only one cassette size will fit optimally (probably somewhrere in the middle of thr range). The further you stray from this optimal size, the less consistent will your shifting be.

I'm not advising against it. It works well enough for many people. I'm just trying to explain what exactly it is you are sacrificing by mismatching.

Short answer, 32t works fine on the short cage 7000/8000/9100 derailleurs. Is it a good setup? Depends how you ride and how picky you are. Not for racing.

by Weenie


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