Zwift hub compatibility with Giant TCR 2021?

I bought a hub this week (an 8-speed was available, and I changed the cassette to an 11-30 11 speed so it matches my bike exactly)
Mounted my bike today to find out the thru-axle doesn’t go completely through.
It’s of about 2mm, you can see it at the drive side where you can see the axle is not aligning with the ‘outside’ of the frame.

And of course resulting in gears not shifting correctly (2mm offset is a lot).

Looking around online showed the same issue for the Wahoo Kickr, apparently, a number of bikes has a little less than 142mm. (Oa Trek, Cervelo and Giant TCR)

Are you Zwift guys aware / planning on new adapters?
Recalibrating my gears everytime I switch between
I tested both the originals + the extra ones that were added in the packaging, but no difference.

Or am I missing out something else?


If your frame is less than the standard 142mm, this is a hyper-specific issue - I don’t know any trainer manufacturer that accounts for that or would offer custom adaptors.

Also worth noting: you may not in fact have a “2mm offset” on the cassette - it’s likely spread between the non-driveside (NDS) and drive-side (DS).

I have a potential solution to your indexing issue, though it’ll require you to take some measurements with digital calipers that have a depth probe on the tail end.

Figure out the distance between the contact point of the wheel hub and the lockring of the cassette installed on the wheel.

Measure the corresponding distance on the Zwift Hub trainer (the face of the DS axle adaptor to the face of the cassette lockring).

If there’s a difference (likely a longer distance on the trainer), install one or more spacers behind the cassette on the trainer so the spacing matches. This will result in your derailleur having the same “offset” between the smallest cog on each cassette, and no requirement to re-index between wheel and trainer.

Your other issue (because of narrower dropout spacing on your bike) is thru-axle length. The solutions here are to either buy the appropriate Tacx Thru Axle Adaptor (works on any trainer, not just Tacx) to give you a longer trainer axle, or grind off some of the thread depth on the NON-DRIVE SIDE axle adaptor of the Zwift Hub so that you aren’t spreading your rear drop-out as wide. (this should not change cassette offset as that’s determined by the DS adaptor and any spacers behind the cassette)

Unless you can source a spare 142mm NDS thru-axle adaptor from Zwift, I wouldn’t modify the one you have - just get the longer thru-axle to facilitate full engagement with the bike’s DS drop-out threads.

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I also have a Giant TCR with a thru axle.

Can you describe a little more what “…axle is not aligning with the ‘outside’ of the frame” means? It sounds like your bike is misaligned enough that the axle isn’t sliding all the way into the threaded (right) side of your frame.

  1. Double check that the axle spacer on the left side (non-drivetrain side) of your trainer is oriented correctly for 142 mm and not 148 mm. You can take the left spacer out of the trainer, flip it 180 degrees, and re-insert. One way will noticeably stick out further than the other. You want the orientation that sticks out less. If you have it in the wrong orientation, your thru axle will seem too short.

If the axle seeming too short is not the issue but rather that the axle is misaligned and won’t engage the threaded part of your frame:

  1. Remove the bike frame out of the trainer. Shift your rear derailleur all the way rightward (i.e. as if it were positioned under the smallest cog).

3a. Put the frame back on the trainer, but this time take care to align the rear derailleur on the smallest cog of the cassette.
3b. Also make sure that the frame is centered - i.e. perpendicular to the trainer.

@shooj , I was focusing on this section:

I took that to mean the thru axle wasn’t fully engaging the frame - it’s too short, so the end of it no longer reaches the outside of the drop-out on the drive-side of the frame. This would be the case if the bike drop-out spacing is narrower than the spacing on the trainer. (thru-axle not long enough for full engagement)

Here’s a photo of what that looked like on one of my bikes before I addressed the spacing issue:


If you get the spacing right, you should see this:


I’ve spent most of my working like in the bike industry and can say with 99.9% confidence that’s not the case with the OP’s 2021 model year bike from a major brand like Giant.

In the early days of disc brake adoption on road bikes (we’re talking ~2014 - 2017) it took a few model year cycles before frame manufacturers fully implemented the now-common 142 mm frame spacing + Direct Mount disc caliper standard(s).

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Good info @shooj! I have some bike wrenching experience but likely not that kind of deep model year knowledge.

Someone on Reddit had what might be a similar issue that turned out to be over-tightening the Drive-Side thru-axle adaptor. Now I’m wondering if that’s what’s going on.

I checked with our Hardware team and some of the trainer’s axle ends for thru-axle bikes shipped in the first round (early October 2022) may be out of spec and cause the symptom you described.

We are confident that this will be sorted out in future shipments of Zwift Hub.

For those who received their trainers in the first round of orders - please contact Zwift Community Support via email and we’ll send out replacement axle ends. This must be done via email using the provided link to protect your private information.


Thanks for all the feedback. The issue is indeed the axle that does not go competely through like in the pictures from @Otto_Destruct

Ik saw the follow up on the new adapters, so thumbs up for the Zwift team, only thing is i think i have the new set already (there was a 2nd set in my box).

Had some time to take some pictures today and I think I found the issue.

You can see on the pictures there is an extra ‘ring’ that goes a little deeper at the inside of the drive train side of the frame where they they axle connects.
Looking closer to the connection sticking out of the wheel, it also becomes a bit smaller at the end.

Ik think this is the reason the wheel falls just 1 or 2mm deeper in the frame.

I’m handy with bikes but not an expert. So I don’t know if this makes sense?


I order my Zwift hub in the second round about November 7th, but I didn’t receive the adapter as it is described here.

I already contacted the Link for the community support but I wanted to know if there’s something else I could do.

Thanks in advance,

We have an entire team handling support specifically around questions about the Hub trainer.

It sounds like used the Contact Us link - were you able to reach a human who got your shipping address? We don’t handle that on this forum to keep your private information private.

Hi, i have the same problem with my Giant TCR. Were you able to solve the problem?

Hi, i have the same problem with my Giant TCR. Were you able to solve the problem?

I didn’t solve it. There is still a 1-2mm difference, but I have been using the trainer now for months, and didn’t feel any issues.
When spring returns, the issue will be bigger when I switch between trainer and wheel more often, but for now I could live with it.

Ok, my gearing is off. When shifting it skips a gear.

Did you switch adapter? Which adapter are you using?

I just adapted my gearing a bit. I mostly ride with ERG mode on, so I don’t shift (a lot).