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 . I’ve perhaps implicitly made some incorrect assumptions above so if someone more intelligent than me could point them out, I’d be grateful . Thanks again for your suggestion .
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 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 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!
I am having the same issue where Zwift is not matching Garmin. For example, I just did a 5k run and Garmin showed 3.1 miles but Zwift showed 3.29 miles which is too much of a disparity. I think I am going to use Zwift calibration and set the normal running speed to 10.5 kph instead of 12kph which is what is sctually closer to normal running speed. Hopefully that will fix it.
Likely the issue here is that for Garmin watches you need to set the speed and distance source to be the footpod and set the calibration to be done by Stryd instead of Garmin. That last piece is important else your speed through the watch is being adjusted by the watch before going to Zwift vs pairing directly.
I am using a Garmin Marq Athlete combined with Zwift using my BowFlex BXT56 (EU) / T22 (US) treadmill.
At first I connected Zwift to Garmin Connect and to Stravia to sync my runs. It worked nicely and I did not switch on my Garmin watch activity, the run was synced anyway. Then I noticed that such synced activities are actually not calculated as ‘running’ in Garmin challenges nor are they used to calculate VO2 Max. So I decided to switch on Virtual Run on my Garmin when I start running on the belt at approx. the same time I switch on Zwift.
The result is both runs are saved on my Garmin account, but they have serious differences, like 10 to 11km. Most likely I am guilty for myself as I have used the calibration settings after such run. My mistake was: one of the device was actually started later (I think I walked a distance before the second device was started). I was/am not offered such calibration after that first run.
I’d like to ‘re-calibrate’ the treadmill to my Garmin, anybody know how to do this.
I tried ‘Settings’ - ‘Sensors and Accessories’ but there is no treadmill shown here.
I also went to ‘Settings’ - ‘Activities & Apps’ - ‘Virtual Run’ , also here I did not find a calibrate option.
After you complete your run using virtual run it should give you the option to calibrate and save on your watch.
If you marry this distance up with that of your treadmill it’ll get more accurate the next time you run.
Hopefully the treadmill distance and Zwift distance will match.
The Garmin distance should upload what you tell it on the watch but stage will only report the distance of your watch before calibration.
You are very right. After I finish a run in the menu on my watch I can scroll down and it will show a ‘calibrate & save’ option. After ‘re-calibrating’ like this, the numbers fit a lot better. I understand that the distance match only if your speed is approx. the same, though. If I run at 80% of my usual speed, I notice a difference. My logic is, that a change in stride length and cadence is difficult for the watch to notice and recalculate.
That’s correct, it will only stay close to matching the pace of you stay at the constant speed. I’ve noticed test anything up to 0.5km/h difference in pace is difficult for the watch to register the difference.
I guess arm swing doesn’t correlate to leg speed when changing pace.
. I’ve perhaps implicitly made some incorrect assumptions above so if someone more intelligent than me could point them out, I’d be grateful 
. Thanks again for your suggestion 
.