Zwift Hub Autocalibration [Firmware v4.0]

A new update for your Zwift Hub is ready! Install the latest firmware now to get a helpful new feature: auto-calibration.

Upgrading your firmware is easy. Open the Zwift Companion app, and you will see a prompt that a firmware update is available. Having trouble finding it? You can also check and update the firmware by navigating to ‘More’ > ‘Zwift Hardware’ and then selecting your trainer.

A video and written guide on how to update your firmware can be found here.

What’s included in the version 4.0 Zwift Hub firmware release?

  • Auto-calibration optimizes the accuracy of the power reading from your Zwift Hub and happens automatically during rides.
  • This works similarly to a manual Spin Down Calibration. After the first minute of riding, auto-calibration will be triggered at any moment during your activity when you coast for at least 5 seconds from a speed of at least 15 kph / 10 mph.
  • So next time you’re pausing for rest, freewheeling down a hill, or coasting to a stop at the end of your ride, your Zwift Hub will be automatically optimizing itself.
  • Firmware will be available to all Hub owners in phases over the next week.

UPDATE March 27 2023
Hub firmware v 4.0.1 has begun rollout.

  • Fixed HR pairing bug.
  • Calibration accuracy improvements.
  • v4.0.1 is available today if you’re already using v4.0.0.
  • v4.0.1 will roll out in phases if you’re using v3.9.

Does anyone have any detail on whats in the latest ZwiftHub V4 Firmware update?

Given Zwift’s recent history with release quality, I am not going to update mine until I see release notes AND hear that it isn’t causing problems for people.

It should not have been released without this page having been updated (it isn’t yet):

Updated mine right before the ZRL race tonight. Worked like a charm during the TTT.

Merged your thread into this one.

@shooj Just done this, seems to have worked, connects and rides ok but light is flashing red…any ideas what I should do? companion app says firmware up to date

Well, I made the mistake of trying to update the firmware on my Zwift Hub before an event and now it won’t connect to the Zwift App running on my Windows 10 PC anymore. It says “No Signal” on the pairing screen and I haven’t been able to resolve it. I’ve tried restarting the hub and the PC, but it appears that the hub just won’t hold the connection anymore. On the Windows bluetooth settings panel, the hub flips between saying “Connected” and “Paired” and the blue light on the hub doesn’t stay solid, but occasionally blinks (not like when it isn’t paired). Eventually it will throw in some purple and red colors too.

But now I’m basically stuck without being able to use the trainer at all. Has anyone else experienced this? Is there a fix I can make?

Update: The trainer does seem to connect just fine to my MacBook Pro, so it might just be an issue limited to connecting to Windows PC’s. I’m not sure. I’ll try doing a ride tomorrow with the Mac and see how it goes, but it’s not my preferred setup.

Same as Chris above, I get a flashing red light and power feels “off”. Otherwise it connects and works seemingly fine with no dropouts just the constant flashing red light…

I have been told by support that the unit is going to be replaced.

Just received a new Zwift hub, to replace my unit that failed on the upgrade to firmware v4.0, and it came with firmware v3.8 and told me an upgrade was available. I did the upgrade, it succeeded and now says Firmware is up to date and the version is 3.9
Have they pulled 4.0?

1 Like

I decided to hold off on installing v4 given how many issues I was seeing others have. I’m no longer seeing v4 as available on Companion either. I really wish Zwift (@shooj ) would respond here with more information. I’ve tried dealing with support by email, but that’s basically a joke.

1 Like

I got my Zwift Hub 4 days ago and firmware update was at 3.9. Checked yesterday and no change.

I spent a bunch of time Friday on Zwift support chat trying to ask why I couldn’t update to 4.0 even though I had been getting the update messages all week. I was/am not able to manually calibrate so I thought 4.0 would help me despite my reservations. None of the support staff I chatted with knew (or will willing to say) that the firmware rollout was suspended (presumably due to these issues), but a reddit post late Friday confirmed that it has been pulled. Now I am glad I didn’t update when it was available to me. Sorry to those who took the plunge and regret it.

Hey everyone -
We’ve been investigating why some returned units are not taking the firmware update as expected. Thanks to all those who’ve been working through this with us! There’s a few steps we’d like to detail

Before updating firmware

  1. Verify you’re using the latest version of Zwift Companion. Please check our Latest Version thread, and confirm build numbers on the Google Play Store / Apple App Store
  2. Keep the phone within line of sight of the Hub trainer.
  3. Do NOT let the phone sleep. Be sure your phone is charged fully, or plugged in to AC power.

If you attempt a firmware update and it fails:

  1. Force-close the Companion app and re-open. Rebooting the phone would ensure a clean restart.
  2. Do not press the Forget button in the Companion app.
  3. Do not uninstall and reinstall the Companion app.

If several attempts fail, contact us for next steps.


Is the auto calibration only done when riding with Zwift?

Currently I use my bike computer (Garmin Edge) for some trainings and I was wondering whether calibration is needed there or not.

1 Like

One of the first things I was advised to do was delete and reinstall the companion app!
That obviously didn’t work and I now have my replacement unit up and running.
I am, according to the companion app, up to date with the firmware, which is 3.9. Does this mean I don’t have auto-calibration at the moment?

Once the Hub trainer has been updated to firmware v 4.x or higher, the trainer itself has the ability to autocalibrate. Autocalibration will work with other apps, in other words/

Correct. We are rolling out firmware v4.0 in phases. It will be available to all Hub owners to allow autocalibration soon.

1 Like

9 posts were split to a new topic: Heart Rate Monitor not paired to Hub Trainer after firmware update [v4.0] [February 2023]

I have owned my Hub since late October and it has worked flawlessly up until the last firmware update. I have the latest update on both Zwift and the Hub. Actually if I remember correctly both update were done on the same day. I am using a windows 10 pc connected with a ethernet cable and a Android tablet for the companion app. I am continually losing the connection between the Hub and my computer. The power, cadence and HR just go blank. It happened 3 times last night while trying to ride with Maria. The only way i have been able to re-establish the connection is to exit the game and restart and it works for thirty minutes and the process starts over again. I am also unable to connect to the bluetooth straight thru my computer, i have to run it through the companion app. I have tried turning blutooth off the on to re-establish the connection and making sure there is no interference between the Hub and the computer with no change. Any help or suggestions would be appreciated.