Question about calibration of smart trainer after being powered off

Hello everyone,

I recently purchased a Saris H3 smart trainer and have a question regarding calibration after powering off the trainer. Do I have to go through the calibration process each time the trainer is powered off and back on?

No, the calibration is stored in the trainer and isn’t lost when you power it off. Always calibrate via the trainer manufacturer’s app, and not through Zwift.

The calibration will drift over time so I calibrate every couple of weeks or if there’s been a large temperature/humidity shift in my trainer area. But as Steve said use the manufacturer’s app to calibrate and not Zwift’s.

Having used the Saris app to calibrate my H3 that I’ve had since around April '22, which gets turned off after each day of use, the app recalls the last calibration rolldown value.

I wonder if I’ve not calibrated my H3 often enough (maybe ~8 times over ~18months, when I’ve not used it for a while or the ambient temperature has changed significantly).

I also wonder if sometimes calibrating after very little warmup is affecting accuracy (but then I often race/ride without warming up and my sessions are usually 15-45mins).

Then there’s the question of calibration method too. The other day I increased speed very slowly and only selected the next hardest sprocket when the power reading had dropped down to 50W when resistance dropped off. In the past, I’ve let it reach 50W when I initially pedal for ~10secs and then steadily move through the gears without caring about the reading.

I’m a little dubious about the power readings I got from the Tiny Races on 26th August, where I got a zMAP promotion from race 1 up Watopia Hilly KOM in both zone 1 and 2, with 5min efforts of 304/315W respectively (344/354W up KOM itself).
The very slow calibration the other day gave a weird 6-digit rolldown reading (starting 14xxxx and it felt harder than expected afterwards), so yesterday I did a “factory reset” in the Saris app, which said previous rolldown was 14.1secs and it was resetting to 13.9secs.
I then did a Zwift Hill Climb season 4 event 1 up Hilly KOM and apparently I did 369W for 2min33secs, so a bit higher than late August. I was absolutely wrecked after it and still feel rough today, so regardless of power accuracy, it was a big effort for me.
But in the last week, I’ve done two rides outdoors on my road bike which has a 4iiii Precision 2 left crank power meter fitted, where my best 2mins30secs was 316W and best 5mins was 293W, from a single short effort on each ride… Could be fatigue, but heck of a difference from the Saris!

no, but in my short experience with the saris h3 i found it needed calibrating a lot more than the manufacturer recommends

How often are you or did you calibrate your H3?

How did power numbers compare to any power meter on your bikes, taking account of drivetrain losses, where I believe a clean drivetrain would produce ~3% less at the rear hub compared to a crank meter?

I never expected after ~18 months ownership to still not have switched my H3 from q/r 9-speed to bolt thru 11-speed, so I could compare power numbers against my 4iiii. But it’s pretty low on my priority list while my own battery is messed up from long covid for almost a year now.

personally i did it at the end of every ride, although i’m just that kind of person. so the numbers weren’t miles off, but the first 20 minutes of every ride it would read low (starting at a good 10% lower at peak pwr and then gradually getting better) which was very annoying and considering i dont put out of a lot raw power to begin with, very noticeable too

but the reason i ditched it though was it developed the knocking sound that they are apparently famous for within 2 months, and when i tried to open the f*cker up to take warranty photos i realised one of the 7 or 8 big allen key bolts holding the side panel on was out of tolerance and stuck since none of the standard sizes fit and i wasn’t about to drill it out. i think it’s still sitting in outdoor storage. i’ll get around to refurbishing it and putting it on ebay one day, but one of the big mysteries of my life will always be how they managed to screw that bolt in, in the first place. they are built like tanks so they have that going for them

consider dual recording a ride or two. i do ride in an uninsulated shed, though i had a direto x before that and it was absolutely fine for up to three weeks (a little on the high side if anything). no need to bother with any of it now thankfully as i swallowed my pride and bought a kickr

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