Zwift running speed disagrees with Garmin yet they each use Stryd!

My Zwift running set up makes use of my Stryd foot pod as a speed / cadence sensor.

My Garmin Fenix 5X Plus also makes use of Stryd for when I select “Treadmill Run” as a new activity.

I’m therefore a little baffled as to why when measuring the same run using both methods (as described above) the Zwift measurement is appreciably slower. They each use the same (Stryd) sensor! By way of an example, a recent 6k (treadmill) run was measured by Zwift at a pace (in min / km) of 4:10 / km but the Garmin’s pace was 4:00 / km. These paces translate to around 14.4 kph and 15 kph respectively and for what it’s worth, the latter is closer to the speed shown on the treadmill.

Any ideas why these two measurements are so different when using the EXACT SAME measurement device for the EXACT SAME run?

Did you do a treadmill calibration on your Fenix before you got your Stryd? I know the 1st time I used my Fenix in treadmill mode after I was done it prompted me to adjust the distance to match what the treadmill stated (calibrate the watch to your treadmill). If you did this that probably would explain the difference as Zwift doesn’t have that calibration factor info.

Many thanks for the idea. I didn’t do this (rarely used the treadmill before Stryd) but even if I had I think the point is that the Garmin now relies on Stryd for treadmill runs. In the absence of a footpod like Stryd I understand it uses data from your arm swing and the like which makes It necessary to carry out the calibration you describe. Now when I select the ‘treadmill run’ activity it tells me it’s using Stryd (and indeed verifies the connection to Stryd on the watch display). So this means, the Fenix is using Stryd AND Zwift is using Stryd - yet I get two differing speeds :exploding_head:. I’ve perhaps implicitly made some incorrect assumptions above so if someone more intelligent than me could point them out, I’d be grateful :grinning:. Thanks again for your suggestion :+1:.

No you are right, in treadmill mode the accelerometer is used to estimate your distance. You can then calibrate this at the end of your run with the hope it’ll get more and more accurate.

If you’ve paired the Stryd then this would override this.

I can’t think why you’re getting contrasting data from the same device.

Thanks Stuart. I can also see the difference in real time when I glance at my watch pace and then look up to see a slower pace on the Zwift screen. A bit demoralising to have to work appreciably harder just to keep up with others :grinning: and compromises my enjoyment of Zwift running to be honest. I will post this on the Stryd forum too and report back if there’s a resolution.

Though I’m using a garmin footpod I can’t be sure if my solution helps.

My Fenix 5plus uses a calibration factor of the footpod while zwift uses it’s own calibration by testing the footpod on various paces. Result: 0,2 - 0,4 kph difference between watch and zwift. But the calibration factor on my watch is changeable inside the settings (sensors >> footpod >> calibration factor) very precise (0,1 steps) so I can synchronosize the pace if I want to.

Thanks everyone. I calculated my true treadmill speed using a method I’m not allowed to link to so just put the following into a search engine if you’re interested:

Zwift How-To: Calculating the speed of Your Treadmill. How do you know that your treadmill is reporting the correct speed?

And then calibrated Stryd within Zwift (via the wrench icon) accordingly. The treadmill speed I measured was actually very close to the treadmill reading so I’m happy enough. Unsure why the uncalibrated Stryd was off.

Thanks again to all for the help and suggestions.

Not sure why you weren’t able to add the link, but here it is for anyone interested:

Thanks for that. Just for completeness, I ended up calibrating my Zwift / Stryd combination to be slightly slower than the reported treadmill speed (= actual treadmill speed for me) for a couple of reasons as follows: 1) to match my Garmin / Stryd combination (when you select Treadmill Run on Garmin) which itself had been calibrated following months of outdoor running and 2) without wishing to go too far down some of the technical rabbit holes, there appears to be evidence you are running at slower than your treadmill belt speed because, in a nutshell, your foot slows down the belt slightly when you strike it. See the fellrnr and DC Rainmaker YouTube channels if you’re interested to learn more but hopefully this info is sufficient if you’re not! :+1:t3: