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I have two wheels and two 11 speeds cassettes. With one combination of cassettes and wheels, shifting is reliable. With the other combination, the position of the cassette relative to the derailleur is clearly incorrect and I get a lot of chain noise and spontaneous shifting.

The parts I have are:

  1. Giant P-R2 rear wheel
  2. Shimano 11-34 cassette, CS-HG700-11 (I think)
  3. Campagnolo Calima C17 rear wheel
  4. Shimano 11-30 cassette, 105 R7000

Shimano 105 GS long cage rear derailleur

Combination 1 + 2 is what came with the bike, and works fine. When I disassembled it, there was a shim between the largest sprocket on the cassette and the wheel side end-stop on the freehub body.

Combination 3 + 4 also works fine, without a shim, on the same bike without altering the adjustment of the rear derailleur at all.

However. I want to use the old wheel with the new cassette (1 + 4), indoors on a turbo trainer, and the new wheel and the old cassette (3 + 2), on the road.

Neither 1 + 4 or 3 + 2 works satisfactorily with or without the shim - either I can't get the nut thing to engage the threads to hold the cassette on, because the shim pushes the cassette too far out from the wheel, or without the shim the cassette is too close to the wheel and I can't adjust the derailleur such that shifting works with both wheels.

Questions:

  • Should I expect combinations 1 + 4 and 3 + 2 to work?
  • Should I need a shim?
  • If I do need a shim, is there a particular width or part number I need to look for?
  • Am I missing something obvious?

Thanks

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  • Both cassettes are 11 speed road and should have exactly the same width and sprocket spacing (feel free to measure to confirm). If one requires a shim then the other should as well, on the same wheel. I’m at a loss here. It’s expected that you’ll have to re-adjust the derailleur when swapping wheels.
    – Michael
    Oct 13 '20 at 10:11
  • 3
    @Michael Shimaho 11-34 cassettes require a spacer
    – Paul H
    Oct 13 '20 at 16:41
  • I’ve had a cassette lockring refuse to screw on before. Thoroughly cleaning the mating surfaces of the individual cassette parts fixed it. Maybe give that a try?
    – MaplePanda
    Oct 13 '20 at 19:55
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Although the dimensions of the freehub may be the same, and two cassettes may have the same spacing. The hub dimensions will not be the same.

So the position of the freehub in relation to the frame is difference between wheels. A difference of just 1mm in freehub shift is massive in terms of the way the rear mech aligns to the cassette.

Similar issues have been noted when using direct drive traininers, the gears will be perfectly aligned to the cassette on the wheel, but when you mount the bike to the trainer, the cassette is in a different place in relation to the rear mech, so shifting is not correct on trainer.

There is no work around for this, every time you want to swap rear wheels, if the freehub is in a different position in relation to the rear mech, the shifting will be off and it will need to be re-aligned to the new rear wheel. This means that the old rear wheel will not be aligned anymore.

In terms of combination 1+4, there shouldn't be an issue here. It might be worth taking it to a mechanic to have a look. Without seeing it, it's hard to know what is wrong.

I suggest you make the bike work for when you will use on the road, so have the gears set up for the new wheel and old cassette (ie wheel 3 + cassette 2). And then just be aware that the shifting will not be perfect on the turbo traininer with the old wheel and new cassette.

Edit from comment

Thanks to Weiwen Ng for pointing that that the CS-HG700-11 cassette uses the "10 speed" freehub body. This explains why there is a shim where the 105 R7000 uses the "road 11 speed" freehub body. This could also factor into the shift of cassette cogs in relation to the rear mech.

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  • 1
    Actually, the HG700 or HG800 cassettes need that shim when mounted to an 11s freehub body. If mounted to a 10 road freehub body, they do not need the shim, and I would guess it's the same for an MTB freehub body. This shim might be specific to those two cassettes, since they were advertised as being able to mount to the older 10s freehubs. I have used HG800 cassettes on one older 10s freehub and a current generation 11s freehub.
    – Weiwen Ng
    Oct 13 '20 at 16:48
  • I'll edit to add this, thanks
    – abdnChap
    Oct 13 '20 at 20:14
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See: https://bike.shimano.com/en-EU/product/component/shimano105-r7000/CS-HG700-11.html

Compatible with GS cage rear derailleurs, the HG700-11 cassette offers low climbing gears perfect for mixed surface riding. It is compatible with both 10 and 11-speed freehubs."

The same applies to HG800. The CS-R7000 cassette is for 11-speed freehubs only.

The installation manual for CS-R9100, CS-R8000, CS-R7000, CS-HG800-11, CS-HG700-11 explains: https://si.shimano.com/#/en/DM/RACS001

If installing CS-HG800-11/CS-HG700-11 to a ROAD 11-speed wheel/freehub, install a 1.85 mm spacer first. (A 1.85 mm spacer is not required if installing to an MTB 11-speed wheel/hub"

In other words a 10 & 11 speed MTB freehub is the same, but 11 speed road freehub has a 1.85mm longer body than 10 speed road, which is the same freehub length as 10/11 speed MTB.

So the HG700 is a universal type, for MTB/road 10sp without spacer or road 11sp with spacer, and the R7000 is road 11sp only.

I guess this is the source of the issue.

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  • Ah, thanks, this explains why the CS-HG700-11 needs the spacer. Oct 13 '20 at 16:07
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1+4 should work without the spacer.

2+3 should work but require a 1.85mm spacer.

If drop-in interchangeability is successful with 1+2 and 3+4, then it should work or at least be close with the other combinations as well.

The only way to avoid needing to adjust your b-gap when you switch is to have it set up for the 34 and accept it being bad with the 30.

34t is the start of 11s cassettes that can fit on an 8/9/10 HG freehub body by overhanging the right flange. They're the same width as an 8/9/10 cassette. Adding the 1.85mm spacer makes them the width of an 11-speed road cassette. (Kind of holdover terminology from back when 34t didn't go on road bikes.)

You are saying that putting the 11-34 with its spacer on the Campy wheel (2+3) causes the issue of the lockring threads not being able to engage. So the small cog is engaging with ends of the splines acceptably, but it locates the lockring such that it can't engage the threads. That is unusual and suggests the whole problem is there's some peculiarity with the how that lockring and that freehub are playing together. There are extra long HG lockrings some companies make that solve problems like this. So if it's true that the entire problem with that combination is just getting the lockring to reach down far enough to start screwing on, I suspect that getting one of those plus setting up the bike to shift with 1+4 sans spacer (should be the same RD adjustment as 1+2 and 3+4 or very close) will fix everything.

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  • "So the small cog is engaging with ends of the splines acceptably, but it locates the lockring such that it can't engage the threads. That is unusual and suggests the whole problem is there's some peculiarity with the how that lockring and that freehub are playing together" Yes, this is it I think - in this case the spacer is pushing the cassette, and the lock-ring, just a tad too far off the hub. I'm wondering if I could try an alternative, slightly smaller or differently shaped spacer. Perhaps the spacer I have is specific to the Shimano freehub? Oct 13 '20 at 17:44
  • @NotRelevant It is possible for a manufacturer to come along and make a freehub body that's a little different in length from standard and a different thickness spacer is thus needed. But since the Campy wheel is working with the 11/30, that's probably not what's happening. If you have a caliper you can measure the spline lengths to corroborate. Again, the big clue is that the small cog is interfacing acceptably with the splines at the same time that the lockring isn't engaging. That is an unusual combination to see and if true suggests this is a case where you need a longer lockring. Oct 13 '20 at 17:57
  • In other words, the fact that interchangeability is working with the other combinations suggests that the spacer is as it should be and there's no way of changing its thickness without messing up shift interchangeability. Also if the lockring can't reach down and screw in at all, then it's way too short to be able to torque down without stripping threads, even if the spacer were a millimeter shorter or whatever. Oct 13 '20 at 18:10

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