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Help with gearing needed, Ultegra Di2.

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Help with gearing needed, Ultegra Di2.

Old 09-23-17, 02:23 PM
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Help with gearing needed, Ultegra Di2.

I want to get lower gearing on my stock Ultegra FC-6800, which is 50-36 X 11-32. I also want to retain the sweet Shimano shifting, so I'd prefer to stick with Ultegra parts.
Ideally, something like a 46-34 X 10-34 (don't know if even exists) would be the range I'd be looking for. Any recommendations (or pitfals) greatly appreciated.
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Old 09-23-17, 06:35 PM
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Are you sure you have an FC-6800 with 50-36? They come from Shimano with 53-39 (full), 52-36 (mid) or 50-34 (comapct). The only way you have a 50-36 is if someone changed the rings.

I own Ultegra 6800 Di2 with 50-34 cranks and am using a SRAM PG-1170 11-36 cassette. It shifts fine in my bike but I can't guarantee that it will shift on anyone else' bike.

You could go with a Sugino OX91D compact crank or any number of other ultra compact cranks.
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Old 09-23-17, 07:09 PM
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Originally Posted by TimothyH
Are you sure you have an FC-6800 with 50-36? They come from Shimano with 53-39 (full), 52-36 (mid) or 50-34 (comapct). The only way you have a 50-36 is if someone changed the rings.

I own Ultegra 6800 Di2 with 50-34 cranks and am using a SRAM PG-1170 11-36 cassette. It shifts fine in my bike but I can't guarantee that it will shift on anyone else' bike.
You're right, mine is 50-34. Wow....11-36, you're running a long derailluer, right.
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Old 09-23-17, 08:42 PM
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Originally Posted by shakey start
You're right, mine is 50-34. Wow....11-36, you're running a long derailluer, right.
Yes. It is a Shimano GS derailleur. Particular attention has to be paid to chain length and as I stated, it works flawlessly on my bike but others have had less than perfect results. I make no guarantees.

The build thread is Niner RLT 9 RDO Build - Bike Forums

I sometimes wish the gearing was lower, especially when in the true mountains. I'm talking 2 miles at 12% grade, that kind of thing. The truth is that going from a 32 tooth sprocket to a 36 tooth sprocket is going to get you a little lower but not a whole bunch. Four extra teeth wont feel magical.

The photo below is what it looks like cross chained. The derailleur is pretty stretched. I crosschain the crud out of it like this all the time. It was built to ride, not to worship.



If you want significantly lower gearing then you are going to have to change the cranks or run an wolftooth road link derailleur hanger extender and a much larger cassette.

I'm sure others with experience will chime in.


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Old 09-23-17, 09:02 PM
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The new ultegra rd-8000 gs derailleur is compatible with up to a 34 tooth cassette and there is a 11-34 r8000 ultegra cassette. Granted you will have to buy the new rear derailleur but it is compatible with your 6800 shifters and matches up almost exactly with your desired gearing. If you want to go even lower you can also get the wolftooth tanpan which allows compatibility between road shifters and mountain derailleurs so you can use an XT or XTR rear derailleur allowing up to a 11-42 tooth cassette.

Edit: just realized you said you are on di2 so scratch the part about the tanpan and xt/xtr derailleurs.

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Old 09-25-17, 10:03 AM
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Originally Posted by TimothyH
Yes. It is a Shimano GS derailleur.
-Tim-
Thanks for the insight. As a followup, do you happen to know if the long cage arm of the 6800 derailleur be retrofit to my existing "medium" mech?
I have read some older posts re the use of K-edge retrofit cage, but don't know if it works well. Also, in looking up the specs of the GS mech, it says it only goes up to 32t, so I'm still and forever confused.


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Old 09-25-17, 10:57 AM
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Originally Posted by shakey start
Thanks for the insight. As a followup, do you happen to know if the long cage arm of the 6800 derailleur be retrofit to my existing medium mech?
I have read some older posts re the use of K-edge retrofit cage, but don't know if it works well. Also, in looking up the specs of the GS mech, it says it only goes up to 32t, so I'm still and forever confused.
there is no "long" his(GS) RD is a medium cage made to clear a 32 but usually is way more flexible. The short cage(28t) is used with 32T cassettes all the time. IF you need more clearance try the wolftooth roadlink
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Old 09-25-17, 09:00 PM
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Shimano supports only 32 tooth cassette with an 6870 GS derailleur. A 36 tooth cassette works on my bike but the configuration is not supported by Shimano.

At lease one person used a Deore LX 10-speed cage on a 105 11 speed derailleur and was able to use a 40 tooth MTB cassette. I don't know about the K-Edge but for a bigger cassette I would not hesitate to use a Wolftooth.


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Old 09-26-17, 12:50 PM
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Originally Posted by shakey start
I want to get lower gearing on my stock Ultegra FC-6800, which is 50-36 X 11-32. I also want to retain the sweet Shimano shifting, so I'd prefer to stick with Ultegra parts.
Ideally, something like a 46-34 X 10-34 (don't know if even exists) would be the range I'd be looking for. Any recommendations (or pitfals) greatly appreciated.
This is almost exactly what I have. 46/34 Ultegra 6800 rings, 11-32 cassette on a 6800 GS rd. I doubt you can put a 10T cog on your current wheels, but don't quote me on that. At some point I will probably put on an 11-36 and have no doubts at all that our 6800GS rd will be able to handle it. And I know for sure it will handle 11-34 but that isn't much of a change in low gearing from 34-32.
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