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I'm replacing the cassette and chain on my Cannondale Synapse 2016 bike, and really struggling to understand where the spacers go on the cassette. No combination seems to work properly when changing gear.

The groupset is Ultegra (11-speed Di2), the new cassette is the Shimano CS-R8000 11-speed 11-32T, the new chain is the Shimano CN-HG701-11, and the hub is Hunt 11-speed (Hunt Limitless 48 wheel). So I believe everything is compatible.

The cassette came with 3 spacers and 11 cogs in 8 sections (11-12-13-14-16-18-20/22-25/28/32T). From research on the interwebs, it seems that I should use 1 spacer with a road hub. This is what I've tried so far:

  1. One spacer below (ie behind) the 32T cog
  2. One spacer below the 18T cog
  3. One spacer below the 16T cog (I think this was like the old cassette)
  4. Combination of 1 and 2 above
  5. Combination of 1 and 3 above
  6. Combination of 1, 2, and 3 above (lockring won't lock properly like this)
  7. No spacers - I'm going to try this next, but not hopeful as cassette will be even more loose than with one spacer.

None of the above combinations work properly when changing gear. With 1 spacer, the cassette seems too loose. With 2 spacers, the cassette seems stable, but won't engage the 32T cog properly and also refuses to change past the other cog with the spacer. With 3 spacers, the cassete is stable, but the lockring doesn't lock and gear changing doesn't work.

Does anybody know the right combination of spacers that should work?

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  • By below the 32t cog, do you mean behind the 32t cog?
    – Weiwen Ng
    Commented Jan 5, 2023 at 23:47
  • @WeiwenNg, yes.
    – HTTP 410
    Commented Jan 5, 2023 at 23:49

1 Answer 1

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On Shimano Ultegra and DA-level cassettes, the biggest 3 cogs come pinned together with an integrated spacer for the smallest of the 3 cogs. The next 2 cogs are pinned, also with an integrated spacer for the smallest cog. The next 6 are loose, i.e. they come as single cogs. However, the smallest two cogs have spacers integrated as well.

One thing to clear up. It sounds like you may be putting a spacer between the 32t cog and the freehub body. Don't do this - there are some circumstances where you would put a separate spacer in this location, but they don't apply to you.

The spacers should go between the 18t and 16t cogs, the 16t and 14t cogs, and the last goes between the 14t and 13t cogs. (The 12t cog has an integrated spacer, as does the 11t.) That is, you need to use all 3 of the supplied spacers. I think that when you assemble the cassette, the last cog may feel like it's hanging off the edge of the freehub body. Nevertheless, you should be able to tighten the lockring down. You can confirm by looking at the cassette and seeing if all the cogs are evenly spaced apart.

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  • Many thanks for the info. I'll try this shortly and mark your answer as correct if it works properly.
    – HTTP 410
    Commented Jan 6, 2023 at 0:05
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    As I sit here with an 11-32 in front of me, I concur with Weiwen's answer. One more thing to note, there is no spacer behind the 32 tooth cog - this is an 11 speed road cassette and I would assume an 11 speed road freehub. No spacer behind the cassette.
    – Ted Hohl
    Commented Jan 6, 2023 at 0:21
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    34t is the beginning of the large cog tooth counts where you need the 1.85mm spacer for 11 speed road freehub compatibility (36.85mm long freehub splines). 32t large cog 11-speed cassettes don't overhang the flange in that way and so they don't take the spacer and can't go on 8/9/10 freehubs (35mm long freehub splines).
    – Nathan Knutson
    Commented Jan 6, 2023 at 0:33
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    Shimano installation instructions: si.shimano.com/en/pdfs/dm/RACS001/DM-RACS001-03-ENG.pdf CS-R8000 is on page 9, with a nice diagram. I was surprised the user's manual doesn't have a diagram. Also, in my experience 105 cassettes are identical to Ultegra cassettes, but 105 cassettes have a different color and a steel lock ring in place of the aluminum lock ring on Ultegra cassettes (to make the Ultegra cassette weigh less?).
    – Andrew Henle
    Commented Jan 6, 2023 at 12:31
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    @NathanKnutson - thanks for the follow up/confirmation there. Paraphrasing: Up to the 11-32 11-speed Shimano cassettes, the full 11-speed freehub is used/required. The slightly larger 11-34 11-speed Shimano cassette, it is branded a road cassette but it fits the narrower 8/9/10 freehub. In fact the 11-34 cassette ships with a 1.85mm spacer included to allow it to mount on an 11 speed freehub. It can also fit an 8/9/10 freehub without the 1.85mm spacer.
    – Ted Hohl
    Commented Jan 7, 2023 at 22:07

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