Zwift Hub axle spacing / spacer too large

In case this is of use for Zwift Hub users; I received my Zwift Hub w/ the 12-speed cassette. To work with another bike, I went to swap the 12-speed for a 10-speed QR config. I reached out to Zwift for help with this, they said send the first unit back and sent me a second Zwift Hub, which has the same issue, so this 1) may be pervasive and 2) isn’t something that Zwift Hub support seems to understand.

The first indication that something was wrong was that drive side QR/thru-axle adapter wrench flats were recessed within the cassette (first image below). To get the adapter out I first had to remove the cassette lockring, which gave me enough clearance to get a cone wrench on the flats. That’s not per the instructions on swapping out the QR/thru-axle adapter, so that made me think something was wrong.

I also noticed the pawls on the freehub are visible (second image below). That’s counter to the “Changing the Freehub Body on Your Zwift Hub” instructions. So, another thing that’s wrong.

The final other symptom I noticed with the whole thing is that, with the correct QR adapters installed (in the correct orientation), I still need to pry my 10-speed frame dropouts apart to get them to fit over the axle. Eyeballing it (not measuring it) the distance the pawls stick out is about the same distance I need to pry the dropouts apart. It’s not much, but it’s noticeable.

I think the issue is that the axle spacer is too long (third image); when I pull that spacer out, the freehub body installs fine and the pawls aren’t visible (final image). I’d not want to run the Hub that way though since tightening the adapter would then load the freehub into the socket, rather than along the axle into the bearings.

Since have two Zwift Hubs with the same symptoms, I think it’s a running problem. I suppose I could track down the correct size spacer, but I would hope Zwift would just have these to sent out to people who have the issue. My long-term worry is that, with the pawls sticking out as-shipped, the freehub will collect crud and fail to work eventually.

Ugh I’m having this exact same issue and I’m trying to figure out if there’s any solution at all?

Otherwise, my 11 cog would have the chain grinding my frame… nope.

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I think putting a smaller axle spacer (or stack of spacers with shorter total length) in place of the one that comes with the Zwift Hub would work. That’s what I tried to get Zwift to do for us, so far no luck on that.

There are kits and such (search for “wheels manufacturing aluminum axle spacer”) so I would guess that the local bike shop should be able to get it setup correctly. Taking the drive-side QR or thru-axle adapter nut off makes it so that the whole cassette / freehub assembly slides off the axle, and the spacer then slides off, so at least getting at the spacer is pretty easy.

When I get a chance (hopefully next weekend) I will try to measure my Zwift Hub to see what’s going on. I was going to measure the total axle length and the spacer length to find how much to reduce the length of the spacer. My worry is that there may be something under-sized on the non-drive side such that even though the drive-side spacer is too long (making the gap and pushing the cogs into the drive-side chainstay/seatstay) the total axle length is correct.

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Update now that I’ve had a chance to tear it apart measure things; using the 130 mm dropout spacing QR adapter, I get an “over lock nut” distance (thanks Sheldon Brown!) on the Zwift hub of 132 mm (I’m probably within +/- 1 mm with the tools I have). Vs the dropout spacing of 130 mm.

Pulling the cassette and freehub, I measure the gap between the lip on the freehub vs the socket shoulder of 3 mm (again, +/- 1 mm)

The axle spacer is 13 mm (+/- 0.5 mm) tall so a 10 mm spacer should get the over lock nut distance down and remove the gap.

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I had the same issue and the lock ring with a 12 speed cassette would contact the dropout on my frame. I solved the problem by filing down a washer which I fit under the drive side adapter. To make things easier to take the bike on and off (and so I don’t misplace it), I place this under the adapter before I thread it on. Attached are photos. The second photo shows where I fit the washer. This makes the overall spacing slightly over 1mm wider as seen on the calper.
Zwift shim1
Zwift shim2

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I’ve also got this gap / exposed pawls. Is this normal for all the Zwift hubs? I would love to have an official reply to this. Mostly because of longevity and potential dust/pet hair build-up.


Just received my hub and I have the same problem.
@Dan_Wait Did a 10 mm spacer solved the problem ?

I didn’t get around to trying it, sorry. I returned one of the trainers and loaned the other to a friend with an… eight speed… road bike

I also have this issue and don’t want to completely re-index by bike each time I change from trainer to outdoor cycling. GCN have a handy YouTuve video about this issue, titled: ’ How To Use Bike Cassette Spacers | Monday Maintenance’

I would rather file down the spacer to 10mm (thanks Dan for the measurement!) or get a new one entirely.

A very annoying and seemingly common issue with the Zwift Hub, so I’d hope they address this by supplying multiple spacer options.

Any luck here? I just got my used hub and rode it once. The freehub pawls were slightly exposed and my gears needed re-indexing. I only had minor trouble getting my dropouts over the lock nuts (10sp QR) but it was enough to note. I then removed the spacer behind the freehub and it looked normal but, as mentioned, the drive side QR locknut pinched the freehub down. I haven’t ridden the trainer for a second time yet but everything seems to work after slightly loosening the drive side QR locknut