Virtual cycling data vs actual data

Why do the Zwift ride logs include virtual ride data instead of actual ride data?

I just signed up for Zwift and had my second ride today. I associated my Strava and Garmin Connect accounts with the Zwift app and my rides are now automatically uploaded to those platforms. For today’s ride, I also logged the event with my Garmin Fenix 6 watch. I expected the data from both logs to match, but they don’t. The Zwift log includes elevation and speed data generated within the virtual ride (fake hills). My Fenix 6 log includes only the real data from my bicycle’s sensors. Since I’m riding in-place using a Cycle Ops Fluid 2 trainer, My elevation never changed nor was my speed impacted by any “hills”.

While I appreciate the in-app feel of presenting the fake values, I suspect most people want real data in their logs to track their actual performance. Thoughts?

The only real data to track the performance is the power (Watt). Speed is always estimated (= calculated, with more or less precision).


So you don’t want your data to show you that the reason your speed went down a lot at some points was because you were climbing?

You want it to show you as riding on the flat for every ride even though your legs felt otherwise?

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Real data is great for the real world - As you are riding in a virtual world the only thing that matters is time & watts as others have mentioned.
The import of hills & virtual speed is a nice to have, and certainly more useful than a flat profile from your sensors.

Hi @Robert_Ramsey1

Welcome to the forums.

I would argue that the Zwift values are closer to reality than a speed sensor on a trainer. Zwift does a good job in “simulating” riding, although Zwift give us very nice bikes and smooth roads so we tend to be a bit faster.

If you log your rides on your garmin deice and that gives you the data you want then just unlink your strava account from zwift and just upload via garmin connect.


Speed is calculated using the circumference of the wheel, and tire, multiplied by the revolutions per hour (miles per hour). Both Zwift and my Garmin are configured for a 700cm wheel and 25cm tire. The speed sensor senses the revolutions of the wheel using a magnet on a spoke. There can be only one true speed. For my trainer, I believe watts are calculated using my speed and the trainer’s resistance profile. Considering the difference in speed graphs between my Zwift and Garmin data sets, I wonder which speed the watt profile is based on, Zwift’s virtual speed or my actual (Garmin) speed?

Using a stationary Cycle Ops Fluid 2 trainer with my road bike, Nothing in the virtual experience is translated into my actual ride experience. I usually just grind out the same training experience I’ve always had regardless of what the computer screen is showing.

If your trainer doesn’t transmit power zwift uses the speed your wheel is moving at and the resistance of your trainer. it then uses this power to estimate how fast you would move on the part of the course you are on.

if zwift estimates you are doing 200 watts this would give very different speeds if you were going up a 5% incline compared to a flat road or a downhill section.

here is an article of how zwift calculates power How Accurate is Zwift zPower? | Zwift Insider.

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Speed isn’t a very useful thing to measure when on a turbo trainer. look at the power output, this is a better measure of how hard you are working.

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I totally believe this is the case. Zwift knows how hard I’m working and calculates an appropriate speed to display based on the virtual terrain. Thing is, in the real world if I’m riding at 17mph, my Garmin records and uploads 17mph. The Zwift app uploads whatever it might have calculated based on whether I was going uphill or downhill. I’m trying to figure out the utility of uploading/keeping any of the Zwift data since it doesn’t reflect my actual experience.

much like in the real world if you are traveling at 17mph downhill this is different than doing 17mph uphill so speed alone doesn’t give you enough information about how much effort you are putting in.


The “speed” of the rear wheel on a wheel-on trainer is essentially meaningless (though it together with known characteristics of the trainer can be used to guesstimate actual power). It may match real-world speeds with a given tire, tire pressure, rider weight, resistance setting (if available), etc., or not.

I’d say “most people” are just fine with this thing just as it is.

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Yes. And I’d never go 50 mph down a mountain…not at almost 60 YO anyway.

I did that a few years ago going over 80 km/h down a mountain on an MTB.
Was scarry BTW

actually, most people riding on Zwift do want to see their Zwift elevation/speed :wink:

and you might call them “fake hills”, but on a smart trainer my legs say otherwise…!

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