Zwift Hub Power Issues

I recently received the Hub after using a Tacx wheel on trainer for a few months. Now my FTP has dropped to a value lower than my first test about 6 months ago. Initial test was 242W and built up to ~260W on the Tacx. With zwift hub it’s now 230W… 12% low? Yikes. Zwift support keeps sending me to articles on the website.

firmware is 3.9 but says it’s up to date. 4 is available? I’ve also reinstalled zwift companion with no success.
I’ve calibrated numerous times after riding 10+minutes.
After one calibration pre-race, I lost all power and had to drop out.

Anyone have advice? Should I ask for replacement? Or buy a different brand? Or just stick to running and swimming?

Accuracy is super important for Zwift races, maybe I’ll just say I’m 10lbs lighter to get my power readings more accurate?

Strange you left out the option that the figure you’re seeing now is more accurate.


It’s hard to guess which one is more accurate without another known accurate power meter. The Flux isn’t it.

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Certainly a possibility lol. My initial test was done on a cycling coach’s trainer when I had literally never biked before. Been working pretty hard since. Maybe I’m just weak af

Direct drive trainers are more accurate than wheel-on trainers. So it’s extremely likely that the Zwift Hub is showing your true power a lot more accurately than your previous trainer, sorry.

But that doesn’t mean that you’ve grown less strong. You’re most probably stronger than before, just that your previous numbers were lying to you.

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So my initial test was done on a direct drive. That was the 242W. This seemed to be fairly consistent with my wheel on Tacx for the last few months. I travel a bit as well, and even the spin bikes and pelotons seemed to align with my Tacx trainer.

I guess the only way to get a true understanding is to get a pedal meter and compare the values.

Comparing the many bikes I’ve used, the Zwift Hub I received was the outlier. That being said, I’ll probably just try a new unit and see if there’s a difference. Not sure it’s worth my time and money to get a pedal meter to search for a 10% power discrepancy.

Also, I couldn’t help but notice these “direct drive” trainers are mostly belt driven…

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I am having the same experience. I formerly had a Kickr Core, which I replaced with the Hub. I also have Assioma Favero power meter pedals. For the five years I had the Core, the Assiomas were pretty consistently 8-10 watts below the Kickr, regardless of the absolute power I was generating. Now, Assiomas are about 10 percent above the Hub. Holding 290 watts on the Hub earlier this week was showing above 320W on my Assiomas (and would have been ~330 on the Kickr). Since I use the Hub to set the resistance, my workouts just got a lot harder.

I don’t know what to make of it. I calibrate everything. The Kickr was a direct drive trainer with an estimated accuracy equal to or better than the Hub, so they really should not be this far apart. Were my old numbers wrong or is the Hub under-stating my power? It’s very hard to say, but it’s certainly frustrating.

The Assioma’s should have always been higher - though admittedly only by around 4% if all things are running well. There is a mechanical lose between the pedals and the direct drive.

On my last ride the Assiomas were 4% higher than the Hub, which is right in line with what you say. The implication is that for the last five years the Kickr Core has greatly overestimated my power and my FTP is lower than I thought. That’s a tough pill to swallow!

I switched from the kickr snap to the Zwift hub and also believe the power numbers are lower. No way to say which is more accurate but I’m certainly not doing as “well” in races and groups. Took some time off in between so thinking I lost a step so will have to see if it improves.

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Same issue. Power numbers are consistently lower than my external power meters. Even more interesting is after I do a calibration my Zwift Hub loses all resistance and I have to exit the game and come back. Very frustrating


Chiming in to say I’m having the same issues. Was previously running a KICKR Core, which matched the power meter on my road bike pretty dang well, but thought it might be nice to have a device made by Zwift. However, riding with the Zwift Hub was IMMEDIATELY different. My threshold has dropped about 30%. Not +/- 2.5% as they say. Every race I do I feel like I’m pedaling through sludge. Firmware up to date.

I gave the KICKR to a buddy so he could jump into the game too, yet now I feel like me trying to spread the love has only ended up biting me in the butt.

How common is this problem?

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