3

Before I start: I know a similar question has been already answered here, but this time it comes with a twist. So here I go:

My setup:

  • 11 speed road hub - stock on on my DTs
  • 11 speed MTB cassette - CS-M7000-11

All the internet's wisdom says one thing: I need a 1.85mm spacer so that the cassette won't wobble. Not it my case:

  • without spacer: cassette fits perfectly. Tightened anywhere between 30 and 40 Nm - no wobble!
  • with spacer: cassette fits, but it sticks out by (what I consider being) a dangerous amount.

You'll ask, so what? Then fit it without a spacer! Problem is, I have another road wheelset, with a road cassette. I want to be able to swap between wheelsets without adjusting the derailleur. Without the spacer, the chainline is messed up.

If I take the cassette from the other wheelset (Shimano 105 CS-R7000) and try to fit it on this hub, then:

  • without spacer: still sticks out, but slightly less so.
  • with spacer: the smallest sprocket won't even bite into the rills on the freehub body. So the MTB cassette is indeed narrower.

The spacer that I have is the one needed to fit 9/10 speed cassete on 11 speed hubs (should be the same). I can't tell the exact thickness, but it is at most 1.9mm. The difference between the amounts the road vs the MTB + spacer cassettes stick out is obviously larger than any error in my measurements. I even cleaned every sprocket and spacer on the MTB cassette to rule out any gunk adding width. Here some photos:

first photo: MTB cassette + spacer (smallest sprocket removed)
second photo: Road cassette (smallest sprocket removed)

MTB cassette + spacer (smallest sprocket removed) Road cassette (smallest sprocket removed)

So my biggest fear is that I'll pull out the thread with the lockring. Around 35Nm it is only about 1.75 rotations in.

Anyone seen something similar before?

UPDATE:

Thanks to Nathan Knutson's suggestion, I snooped trough my old bike parts and found an old 9 speed SunRace cassette, with a lockring a tad thicker. Since the smallest sprocket on that cassette is also 11 teeth, I assumed the lockring would fit so I tried it on: 35Nm and it's already about 2.25 rotations in, much better - considering the Shimano lockring does only have 3 ridges (left in the picture below). Now I only wonder if the smallest sprocket is engaged properly, but given it is only 11t, I don't think there's nearly enough torque to rip off the tips of the splines. lockrings

5
  • Aren't the spacings of 11 speed different between MTB and road ? you might be better putting the same cassette model on both wheels rather than swapping between a road and a MTB cassette. Would you consider upgrading to 10 speed where this would not be an issue ?
    – Criggie
    Oct 20, 2022 at 21:16
  • 2
    @Criggie Cog spacing is the same, the difference is that when the largest cog is 34T or greater, it's dished to follow the path of the spokes so you don't need as wide of a free hub body.
    – Paul H
    Oct 20, 2022 at 23:01
  • 1
    @PaulH some people have taken firsthand measurements and found small differences between the road and mountain cog-to-cog pitch numbers. It's kind of an under-reported topic. See blog.artscyclery.com/science-behind-the-magic/… . Generally speaking it doesn't seem to be enough to matter for the relatively few drivetrain types that even could care about this. Oct 21, 2022 at 2:32
  • 1
    @Criggie when I use the spacer on the MTB cassette then I can swap the wheelset with no adjustments (save the B-screw but that's another topic) and it shifts perfectly. Without the spacer, the MTB cassette is too far in, the road cassette won't shift in the lowest gear (or vice-versa, if adjusted for the road cassette: then the MTB cassette won't shift in the highest). But I do get your point: I might have saved myself some headaches by not mixing MTB and road. They seem to be compatible with each-other when considering just one wheelset, but not between wheelsets.
    – DerMihai
    Oct 21, 2022 at 6:33
  • @NathanKnutson fascinating. I've been using 11 Spd Shimano MTB cassettes with Ultegra and GRX derailleurs for years. Shifting has always felt crisp (when I bothered to keep things well maintained). Given in the numbers in the blog post's tables, I wonder what less traditional mismatches we could get away with.
    – Paul H
    Oct 21, 2022 at 14:19

1 Answer 1

3

The first photo looks about normal, with the splines barely protruding.

If the shoulder to tip length of the freehub body is 36.85mm long like it's supposed to be, and if it's a real CS-M7000-11, then there's not really a lot of places to go here.

Look carefully for any potential obstructions or grime in the freehub body shoulder area that might keep it all from seating.

You were on the right track with cleaning the cassette to eliminate the possibility of grime building up the stack height. It's possible you might need to go a little further with that.

Not wanting to ruin the FHB is a valid concern, but there have been many times I've seen minimal thread engagement like that and when you go to tighten it down anyway, it compresses down more than it seems like it was going to and it's fine.

If the thread engagement just feels wrong, It's also possible that what's going on here is there's already missing/damaged/malformed thread at the start of the lockring threads. Note that the thing that's not perfectly standard in all this is how far inset the beginning of the threads are. Every once in a while, subbing in a longer lockring is needed to help with problems like that. I can't say I've seen it on a DT, but it could still be worth looking at. I don't have any recommendations for what lockring to use in those situations; usually I've just seen what's in the scrap.

4
  • So I measured the freehub body: shoulder to tip (really the end on the hub, where the lockring might bottom down) is, by my measurements, 37mm (probably it is 36.85 - but again, I'm no metrologist). The freehub body is as clean as it gets, I took care of that. It's a shame Shimano does't provide any sizing in the cassette dealer manual.
    – DerMihai
    Oct 21, 2022 at 6:48
  • The thread engages just fine, very smooth. I'm just concerned it is not enough. But I think I will risk it and, worst case, buy a new freehub body - good thing DT made this hand-removable, it would take a matter of minutes. Also very good tip with the lockring-depth: I will look into that!
    – DerMihai
    Oct 21, 2022 at 6:52
  • *> [...] and if it's a real CS-M7000-11, then there's not really a lot of places to go here. * So you're implying the cassette should go no-spacer or with spacer in? One more interesting thing: the seller of the cassette mentioned on the website, a 1.85mm spacer is needed to fit it on a road FHB. But the dealer manual doesn't say anything about any spacer (as opposed to manuals for other cassettes). Guess they're not entirely right, and Shimano is doing something fishy here.
    – DerMihai
    Oct 21, 2022 at 7:02
  • I found a solution, see the edit! Thanks for the help!
    – DerMihai
    Oct 21, 2022 at 14:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.