Larger cassette with Ultegra 6870 Di2 SS rear cage derailleur
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  1. #1
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    Larger cassette with Ultegra 6870 Di2 SS rear cage derailleur

    I have Ultegra Di2 6870 SS short cage rear derailleur with a compact (50-34) front and 11-25 rear.
    I've been trying to spend more time climbing and my aging knees would be happier with larger toothed cogs in the rear cassette.

    The specs for the SS cage state that 11-28 is the biggest I can use. But I see a lot of conflicting information online with people using up to a 11-32 with the SS cage derailleur.

    Are these my options? What works best?
    1. Move up to 11-28 and live with the limitation
    2. Switch to 11-30 or 11-32 and tighten up the B stop to get it to work with a longer chain
    3. Switch to 11-32 and replace just the cage on the rear derailleur
    4. Use a Wolftooth derailleur hanger extension

    Thoughts? Thanks,V

  2. #2
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    This question has been asked so many times it's ridiculous. It's been discussed, argued about, and more. If you switch to 30 it might work, slimmer chance the 32 will work. A rear derailleur does 2 things and burying the b-tension screw only effects one of them. The derailleur has to move the chain to the different cogs (so it has to be able to clear the largest one while still being close enough to the small ones so it shifts well). It also has to wrap the chain you're not using while in small/small(er) cogs. Pay attention here...the SS derailleur you have is only spec'd to clear a 28t cog and wrap (it's capacity) 33t of chain. Let's do the math: 28-11=17. 50-34=16. 16 + 17 = wait for it...33teeth. This simple math leads us to the problem w/ Wolf Links. They move the derailleur so you have more clearance for bigger cogs (at the expense of shifting performance at the smaller cogs) but they don't magically make the pulley cage any longer. That leaves you with 2...ok, 3 options. Size the chain properly and tear the derailleur off the bike when you go big/big, or size the chain long enough to work w/ big/big but most likely still not have the clearance you need in the 32...and a saggy chain in the small ring/smaller cogs, OR...buy the right derailleur for your cassette. Guess which option I'll always recommend?
    #promechaniclife

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    Hmm... I understand. I never cross the chain. Ever ! I'm OCD.

    Buy the right (GS) derailleur or just replace the cage with a medium (GS) cage ?
    I do think 11-30 should be enough. 12-30 would be better as I never use the 11, but I can't find it anywhere.

  4. #4
    'brifter' is f'ing stupid
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    If you're thinking the 30 will be enough I'd try it w/ your current derailleur and see how it goes. There is no such thing as a 12-30 cassette, only 11-30. The only 12 they do is a 12-25.
    #promechaniclife

  5. #5
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    Quote Originally Posted by cxwrench View Post
    If you're thinking the 30 will be enough I'd try it w/ your current derailleur and see how it goes.
    ^^^ This. Give it a try. I've done it numerous times. I've never heard of it not working.
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  6. #6
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    I have a 6800 short cage mechanical and an 11-32 (w/46t 1x). No Wolf link and it works just fine, there's no chain slap etc., though I'm not sure how that translates to a Di2 rear derailleur.

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    Quote Originally Posted by Pisgah2000 View Post
    I have a 6800 short cage mechanical and an 11-32 (w/46t 1x). No Wolf link and it works just fine, there's no chain slap etc., though I'm not sure how that translates to a Di2 rear derailleur.
    Mechanical and Di2 models will move along the cassette identically.

    The OP could also buy replacement inner and outer cage for a 6800 GS derailleur. That would be cheaper than buying a new 6800 or 8000(could use a 11x34 cassette) Di2 GS derailleur.

  8. #8
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    Replacing the SS cage with a GS cage seems to be pretty straightforward and I haven't found any information that indicates that the rear derailleur for SS vs GS cage is different

    https://www.modernbike.com/shimano-u...er-pin-gs-type
    https://www.modernbike.com/shimano-u...late-gs-length

    $24 for the cage. And with this I can fit a 11-32.
    I also have a 12T first cog from a previously sparingly used cassette so I can reduce some of the interim gaps for smoother transitions.

    This will be a fun project.

    Thanks,V

  9. #9
    'brifter' is f'ing stupid
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    Quote Originally Posted by vasuvius View Post
    Replacing the SS cage with a GS cage seems to be pretty straightforward and I haven't found any information that indicates that the rear derailleur for SS vs GS cage is different

    https://www.modernbike.com/shimano-u...er-pin-gs-type
    https://www.modernbike.com/shimano-u...late-gs-length

    $24 for the cage. And with this I can fit a 11-32.
    I also have a 12T first cog from a previously sparingly used cassette so I can reduce some of the interim gaps for smoother transitions.

    This will be a fun project.

    Thanks,V
    So you're gonna have a cassette that goes 12, 12, 13, 14, 16...?
    #promechaniclife

  10. #10
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    Quote Originally Posted by vasuvius View Post
    Hmm... I understand. I never cross the chain. Ever ! I'm OCD.
    Famous last words.

    Quote Originally Posted by cxwrench View Post
    If you're thinking the 30 will be enough I'd try it w/ your current derailleur and see how it goes. There is no such thing as a 12-30 cassette, only 11-30. The only 12 they do is a 12-25.
    Really? I had a 12-30 cassette that came originally on my carbon Synapse with 5700. Do you mean Shimano no longer makes a 12-30?

    Quote Originally Posted by Pisgah2000 View Post
    I have a 6800 short cage mechanical and an 11-32 (w/46t 1x). No Wolf link and it works just fine, there's no chain slap etc., though I'm not sure how that translates to a Di2 rear derailleur.
    46T 1x vs. 50/34. Big difference.

    Quote Originally Posted by cxwrench View Post
    So you're gonna have a cassette that goes 12, 12, 13, 14, 16...?
    So effectively changing an 11-speed to a 10-speed? How will this help once you have the longer cage?
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  11. #11
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    Instead of 11, I could start with 12 and fill in the 11-31 with either a 17 or 19.
    Depends on the config of the 11-31 -- I've never seen one.
    On my 11-25, 21-23-25 are a single piece. On an older 12-28 I have 23-25-28 as the single piece.
    Depending on how the 11-32 is packed, I could fill in one of the missing cogs and still have a 11sp starting with 12.
    Just a thought. Parts are on order and I'll decide when they get here.

    Thanks,V

  12. #12
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    Quote Originally Posted by vasuvius View Post
    Instead of 11, I could start with 12 and fill in the 11-31 with either a 17 or 19.
    Depends on the config of the 11-31 -- I've never seen one.
    On my 11-25, 21-23-25 are a single piece. On an older 12-28 I have 23-25-28 as the single piece.
    Depending on how the 11-32 is packed, I could fill in one of the missing cogs and still have a 11sp starting with 12.
    Just a thought. Parts are on order and I'll decide when they get here.

    Thanks,V
    You still need the second cog that interfaces with the 12T locking cog you intend to put on. In your case that is the existing 12T cog.
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  13. #13
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    Miche makes a 12-30 11 spd cassette for both Shimano and Campy.

    12-13-14-15----17----19----21----23----25----27-------30

    Or go Campy for the 16 and give up 1 cog up top (or add 2, you will need a Campy splined hub):

    12-13-14-15-16-17----19----21----23-------26-------29
    12-13-14-15-16-17----19-------22-------25-------28----------32
    Last edited by DrSmile; 07-08-2020 at 06:20 AM.
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  14. #14
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    I converted the 11-32 cassette on my gravel grinder to 12-32 by using the four smallest cogs from an 12-25 cassette. Kinda sucks needing two cassettes but that’s better than having a 11T that’s never used.

  15. #15
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    Quote Originally Posted by cxwrench View Post
    This question has been asked so many times it's ridiculous. It's been discussed, argued about, and more. If you switch to 30 it might work, slimmer chance the 32 will work. A rear derailleur does 2 things and burying the b-tension screw only effects one of them. The derailleur has to move the chain to the different cogs (so it has to be able to clear the largest one while still being close enough to the small ones so it shifts well). It also has to wrap the chain you're not using while in small/small(er) cogs. Pay attention here...the SS derailleur you have is only spec'd to clear a 28t cog and wrap (it's capacity) 33t of chain. Let's do the math: 28-11=17. 50-34=16. 16 + 17 = wait for it...33teeth. This simple math leads us to the problem w/ Wolf Links. They move the derailleur so you have more clearance for bigger cogs (at the expense of shifting performance at the smaller cogs) but they don't magically make the pulley cage any longer. That leaves you with 2...ok, 3 options. Size the chain properly and tear the derailleur off the bike when you go big/big, or size the chain long enough to work w/ big/big but most likely still not have the clearance you need in the 32...and a saggy chain in the small ring/smaller cogs, OR...buy the right derailleur for your cassette. Guess which option I'll always recommend?
    you should save this reply in a text and just paste it when this question will pop up again!

  16. #16
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    Quote Originally Posted by vasuvius View Post
    I have Ultegra Di2 6870 SS short cage rear derailleur with a compact (50-34) front and 11-25 rear.
    I've been trying to spend more time climbing and my aging knees would be happier with larger toothed cogs in the rear cassette.

    The specs for the SS cage state that 11-28 is the biggest I can use. But I see a lot of conflicting information online with people using up to a 11-32 with the SS cage derailleur.

    Are these my options? What works best?
    1. Move up to 11-28 and live with the limitation
    2. Switch to 11-30 or 11-32 and tighten up the B stop to get it to work with a longer chain
    3. Switch to 11-32 and replace just the cage on the rear derailleur
    4. Use a Wolftooth derailleur hanger extension

    Thoughts? Thanks,V
    why don't you put in a 32t cassette and see if it'll work? If it shifts fine, then you're good to go. If not, then swap in a GS cage. A GS cage WILL make this work. I know this for a fact because I've seen more than a few guys using GS with 32t cassette and all work fine

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    Quote Originally Posted by aclinjury View Post
    why don't you put in a 32t cassette and see if it'll work? If it shifts fine, then you're good to go. If not, then swap in a GS cage. A GS cage WILL make this work. I know this for a fact because I've seen more than a few guys using GS with 32t cassette and all work fine
    In fact, I use a GS derailleur with a 34T and it shifts flawlessly. That doesn't mean it will work for you. It all depends how the chain was sized. Try it in the stand first and go up to the large/large combo VERY carefully to make sure it doesn't bind.
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  18. #18
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    I've ordered a 11-32 cassette and the inner&outer plates for a GS cage. I'll start experimenting once the parts arrive. I have spare chains on hand - definitely think I'll need a longer chain.

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    Quote Originally Posted by Lombard View Post
    In fact, I use a GS derailleur with a 34T and it shifts flawlessly. That doesn't mean it will work for you. It all depends how the chain was sized. Try it in the stand first and go up to the large/large combo VERY carefully to make sure it doesn't bind.
    I know a guy who runs a 36t cassette on his di2 6850 GS der, on a Pina F8 frame, no problem. He put the same 36t cassette/ GS setup on his sister's Cannondale (I don't recall the exact model) and it works too. Yes, he had to crank the snot out of the B screw, but it works.

    Back in the 10spd world, I had once put a 36t cassette with a 105 5701-GS der, on a Serotta frame, and that shifted worked like a charm. No Wolf derailleur extender, no nothing else needed. B screw even had some threads left to spare too! Amazing, Shimano tends to under advertised the specs of their components, it seems!

  20. #20
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    Quote Originally Posted by vasuvius View Post
    I've ordered a 11-32 cassette and the inner&outer plates for a GS cage. I'll start experimenting once the parts arrive. I have spare chains on hand - definitely think I'll need a longer chain.
    just a headsup here. When I changed the cage, there is a spring position that choose. One spring position will yield a tighter tension to the cage, leading to higher chain tension. I believe the default is the tighter tension one. This was the case for 10speed mechanical derailleur. I'm not sure if it's still the case for Di2. But something to note.

  21. #21
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    Quote Originally Posted by aclinjury View Post
    I know a guy who runs a 36t cassette on his di2 6850 GS der, on a Pina F8 frame, no problem. He put the same 36t cassette/ GS setup on his sister's Cannondale (I don't recall the exact model) and it works too. Yes, he had to crank the snot out of the B screw, but it works.

    Back in the 10spd world, I had once put a 36t cassette with a 105 5701-GS der, on a Serotta frame, and that shifted worked like a charm. No Wolf derailleur extender, no nothing else needed. B screw even had some threads left to spare too! Amazing, Shimano tends to under advertised the specs of their components, it seems!
    Well if the chain is long enough in the large/large combo, it will be pretty loose in the small/small and will slap around. I guess as long as it doesn't go completely slack, it's not really a problem.
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  22. #22
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    If you never use an 11 and want pie plate in back for the easiest gear that's an indication that the range you are looking for might be best accomplished by a smaller crank (and maybe also a different cassette).

    Obviously more expensive and may have compatibility issues of it's own though. You'd need to make sure you can move your front der down far enough.

  23. #23
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    Quote Originally Posted by Jay Strongbow View Post
    If you never use an 11 and want pie plate in back for the easiest gear that's an indication that the range you are looking for might be best accomplished by a smaller crank (and maybe also a different cassette).

    Obviously more expensive and may have compatibility issues of it's own though. You'd need to make sure you can move your front der down far enough.
    Not to mention the curvature in the FD may be an issue.
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  24. #24
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    Update: Installed a medium (GS) cage and the 11-32 cassette.
    I've adjusted to derailleur (so much easier with Di2) to work across the cassette both with big and small chain ring.

    But, in the 34 / 32 combo, while I can't see it, it feels and sounds like the jockey is touching the cog.
    The B screw is all the way in. The way the B screw is seated - just barely touching the lip/shelf (?), I don't think I can use a longer screw.

    Wolf does not recommend the Roadlink for a 11-32 cassette.

    I used the same chain as I had with the 11-25 as it fit well and works with the 50 / 32 combo.
    Then I used a new chain with 2 additional links. There is sufficient chain tension but the guide pulley still does not clear the 32t cog.

    Thoughts anyone? Thanks,V
    Last edited by vasuvius; 4 Weeks Ago at 02:11 PM.

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