Smart bike harder than Zwift trainer? - recent transition

I recently transitioned from using the Zwift trainer paired with my bike to a Stages smart bike, primarily in racing. My experience has been that it is significantly more difficult on the smart bike than the trainer. Has anyone else experienced this? Does anyone know if there is a setting or some set up that I need to do?

some background:
Subjectively when I did my first few races on the smart bike, it felt like my legs were exerting about 20-30 more watts than I was getting on the screen. As a result my race performance has dropped significantly.
I tried to come up with some objective data analysis and decided to use Effort (avg HR) over Output (W/kg for 5 min). The ratio on the smart bike was ~20% higher. Granted it is a small dataset at the moment (8 races).
The avg race distances were about the same, settings were all the same, etc. I can’t figure out what the problem is. Fitness is not the issue either.

What were the results of your zero reset of the SB20? I haven’t used a Zwift Hub but my SB20 numbers are close to my (outdoor) power meter numbers. Another thing to consider is whether you have the crank arm length set correctly in the Stages app.

If you’d like to chat with more SB20 users, check out the StagesBike SB20 Owners Group on Facebook.

Thanks for the response. Zero reset was 900 L / 860 R, which was in the recommended range. I don’t have another power meter to compare. I’m also not much of a gear head so I don’t know what to do, if anything, with those numbers. (Respect to all the gear heads out there)
Crank length is ok. All settings are essentially the same, etc.
I’m not a facebook user so I can’t join that group. I’ve searched Reddit, but have found nothing. Also sent a message to Stages support to see if they have insight.

The stages bike should be slightly more accurate thank the zwift hub, it’s possible that the hub was over reading the power

Knew I would see the word Stages the second I saw the topic…

I’ve been riding Tacx Neo, Stages SB20 and is currently on a Neobike and a Kickr Bike v1.
Sorry to say it, but I hated the Stages and everything about. I was never able to produce the same power on it as on my current bikes.
Neo trainer was around the same as my current bike, probably slightly lower due to the flexing aluminium frame that I used on that one.

I don’t think the Stages reports to low ( given you calibrate it constantly :roll_eyes: ), but the huge flywheel and “soft” drivetrain just didn’t fit my ride style - just making it impossible to produce power on it.
On the other hand, it was quite nice for low power endurance rides - but that’s not racing… :wink: