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Speed/Distance on an Indoor Trainer

Relevance of Speed Indoors                       

A common area of confusion involves the relevance of speed readings when doing indoor rides. Are indoor speed readings accurate? Do indoor speed readings matter? The short answer is — no.

TrainerRoad currently doesn't display speed readings during Power or VirtualPower-based workouts. The "speeds" riders achieve indoors are often not representative of speeds they'd be going outdoors at equivalent power levels. Simply put, indoor speed readings can be misleading and don't really add any value to the workout.

Speed Readings and VirtualPower

First, an understanding of what VirtualPower is and how it's derived will be useful in moving forward.

Now that you know speed is used to calculate VirtualPower readings, keep in mind that not all VirtualPower curves (the trainer's speed to power ratio) are very "road representative".

Furthermore, something called "rolling resistance" can affect speed readings indoors. For our purposes, rolling resistance is defined as the amount of pressure placed on your rear tire by the trainer's roller. See the Tire Tension section of this article for more information. 


Speed Readings and Electronic Trainers

Speed readings taken from an electronic trainer set in ERG mode are arguably the least reliable. Having a basic understanding of how ERG mode works will be useful before reading on.

Speed readings are not reliable in ERG mode because the trainer will automatically adjust the resistance to ensure the rider is matching their wattage target — regardless of your gear or speed.

For example, a rider could shift gears and/or increase their cadence to bring their speed from 20-40mph during an interval with a prescribed wattage of 250. In order to keep the rider at 250 watts, the electronic trainer will automatically adjust the resistance to make up for the change in speed. This means the rider's speed readings will indicate 40mph while their watts remain at 250. If the rider shifts back down to 20mph, the trainer will again adjust accordingly so they are still holding 250 watts.

(Incidentally, we recommend that you find a gearing/cadence that suits you and stick with it for the duration of your workouts in ERG mode. Shifting or drastically altering cadence can be disruptive to the workout as it takes the trainer several seconds to adjust.)

Eventual Plans for TrainerRoad and Speed

All of this being said, TrainerRoad is aware of the demand to see speed readings. We have plans to eventually offer a workout display with configurable metrics and something called "VirtualSpeed" (no ETA as of now). 

VirtualSpeed will apply a physics model to a rider's power output. This will, with relative accuracy, calculate the speed and distance they'd achieve outdoors.

Viewing Speed

Although we don't display it live, TrainerRoad does record speed. If you upload your workout via .tcx file to a 3rd party application you will be able to view speed and distance data.  


Option #1 (3rd-Party Site via Desktop App):

1. Open the TrainerRoad app and go to your Career tab

2. Find the workout you'd like to download, and click to the right of the workout's thumbnail for more options

3. Click the "Download" button that will appear

4. Upload the .tcx file to the third-party (Training Peaks, Garmin Connect, Strava, etc.) of your choice.


Option #2 (3rd-Party Site via Online Career):

1. Open the workout in your online Career page

2. Click the "Download" button in the upper, right-hand corner of the screen

3. Upload the .tcx file to the third-party (Training Peaks, Garmin Connect, Strava, etc.) of your choice. 


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  • Avatar
    Farid Akhadov

    I do my TR sessions (mostly steady state) with 2 chunky displays (current and average speed) on my Garmin device along with TR Virtual Power display on my notebook. Even though it's not relevant to road speed, it's still consistent and does force me to keep higher average than previous workout. Also would be nice to have optional average power display during entire session as real time power data naturally fluctuates. Thanks!

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    Steven van Groningen

    Useful article but I seem to be missing something. I understand the lack of relevance of speed/distance in ERG mode but still would like to capture distance for the workouts I upload to TrainingPeaks. Not for assessing my individual trainings but to keep track of total km/year. The distance is always 0 km for the files I upload from Trainerroad. When I open the files in the App in the career tab, speed is also "0". I am using a Computrainer in ERG mode.

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    Sasha Johnson

    When I click Devices before my workout, I do see the speed with the Wahoo Kickr, and it adjusts as I speed up/slow down. However, after my workout, the speed is not recorded. How do I fix this?

    TR may not deem speed/distance relevant, but I like to track it to compare to other workouts & estimate how I should perform on the road. Since races are by distance, not time, I like to track distance trained for a race and a year. It may not be 100% accurate, but it would be more accurate than 0 and training on the same trainer, it should be consistent (consistently write or wrong, it's consistent).

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    Nick Tode

    I now understand the problem, but I'm still left frustrated that the software can't do something to make the data more accurate. I would think that the software could assume that if a 170lb person was pushing 130 watts over 30 min that they weren't going 24mph. Why not adjust the speed (and therefore distance) to be more realistic.

    I ask because I'm tracking my rides on Strava and the mileage being so far off is going to screw up my numbers for the year.

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    catherine courter

    I also track my workouts on Strava
    Would love to know distance so I can track miles per wk/ yr
    Is there a way to calculate this?

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    Lauris Ieviņš

    Why not introduce a "virtual speed"? A speed that is calculated from wattage if you were riding on a flat road with no wind. For that you would have to choose a bike type (Road, TT, MTB) as it affects speed at the same wattage, and the rest is just math. So ERG mode would be no issue with this method.

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    James Morrison

    I care more about distance vs speed, b/c its good to know how many revolutions my gear has had so I can schedule maintenance every x miles vs just counting all this trainer time as zero miles in my Strava odometer. We definitely know mileage - just no idea if it is easy or hard mileage on the total miles on my bike, but I want to know total miles.

    My Computrainer seems to record speed/distance with TR for the first 2-3 segments, and then it zero's out.

  • Avatar
    Alex Kizis

    Hey Everyone,

    I'd like to give you all a quick update about something I think a lot of people will be happy about. :-)

    We plan to implement something called "VirtualSpeed" (@Laruis, great minds think alike ;-))!

    We'll apply a physics model to a rider's power output that will, with relative accuracy, calculate one's equivalent outdoor speed.

    As much as I'd like to provide everyone with an ETA on this, I cannot at the moment. Before we start work on VirtualSpeed, we'll be redoing the code base of our Desktop application and taking care of a few other highly-demanded features.

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    Carlton Bale

    I'm glad to hear Virtual Speed is coming. It will be great for estimating total distance tracking on sites like Garmin Connect/Strava/Training Peaks. Thanks for the update and looking forward to the release.

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    Neil Allison

    When I sync my ride with Strava the Speed/Distance is not shown. I understand it's not much use to me as I ride in ERG mode however it's nice to see me clocking a few miles on Strava even if they are inacurrate. I'm using the new beta software it previously worked on the old desktop software. As a side note the new interface for the desktop is far superior.

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    Kevin Craig
    Ummm... OK, but at least the Kickr electronic trainer seems to read flywheel "speed" or RPM so couldn't that be converted to a 700c wheel and thus speed/distance would be a reasonable estimate?
  • Avatar
    Alex Kizis

    Hey Kevin,

    You're correct. The KICKR does give speed readings calculated for a wheel circumference of 2096mm.

    However, this does not mean that the speed values that are output are necessarily reasonably representative of speeds riders would be reaching at equivalent power levels on the road. Rider weight, gradient, and wind (all variables necessary for the validity of speed as a metric) are not factored into the speed equation indoors.

    Furthermore, depending on a rider's gearing and cadence, indoor speed can be potentially extremely misleading. For example, a rider may do an hour-long, easy workout. Let's say the intervals within this workout range between 30-60% of FTP, but the rider uses their biggest gear for the entire ride. The ERG mode function would automatically adjust the resistance on the trainer so the rider is hitting those low power targets - regardless of gearing. The rider will continue to easily spin through their workout in a high gear, and when they review their workout stats, speed will probably seem ridiculously high given the effort level they just maintained.

    Now, while riding continuously at 35-45mph may be possible outdoors (on a very specific route with LOTS of downhill ;-) ), it's not really considered to be the norm - especially when it comes to an interval workout.

    Even if a rider keeps their chain in the mid-gear range, there's no way to tell if the speeds are representative of what they'd be doing outdoors at equivalent power levels because those essential factors I mention above are not included in the equation.

    I hope this helps clarify things, Kevin!

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    Kevin Craig
    I guess it depends on what someone means by "real" speed. As you note on a flat road with a tail wind someone could easily go 35 mph at 60% of FTP or less. However, if looking at a flat road, the only real consideration, Kickr vs outdoors is wind resistance and very minor (percentage-wise) contribution of rolling resistance. So I just consider myself to be riding in a vacuum - which is what some of the intervals feel like! :D
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    Grant Latimer

    Hi Alex, Whats the latest on Virtual Speed ? I am clocking up so many kilometers on Starva, at this rate my year kilometer goal will be complete by the end of May. I know speed is not important to power training etc, l get all that. However, it would be nice to be able to track a realistic distance travelled. Best Regards G.

  • Avatar
    Alex Kizis

    Hi Grant,

    Sorry to say this, but we don't have any updates on VirtualSpeed right now. :-( Our Development Team is focused on other tasks.

    I know it was nearly a year ago that we announced the eventuality of a VirtualSpeed feature, but we've had to prioritize our development projects according to what's most important (e.g. our new Mac app, an eventual Android app, improvements to training plan features, and more...).

    Sorry I don't have better news, everyone!

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    Pär Willén

    I export the TCX-file from TR and import it into Runmeter, set it as an outdoors ride and thus get speed and distance into my "over all runs"-database. Works fine but, FWIW, I would also like to see it in a configurable TR interface.

    On the name "Virtual Speed" or thereabouts, it's already used by Tacx in their software and it carries a bad reputation due their implementation of it.

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    Michela Barabandi

    I opened a ticket on the issue speed. I can understand and accept that no sped and distance are calculated but wenn I synchronize the activities to other Plattform as e.g Strava or TP a no sense speed and distance are transmitted. Why does have the tcx file values and absurd ones?
    Sorry but without a working interface to other Programms is for me TR a no go! I mean no values is fine but wrong ones are mistaking all my statistics. Do you have a solutions to get at least zero values?

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    Adrian Bennett

    I completely understand this issue but as Strava is able to calculate power for an outdoor ride then it would be really nice if TrainerRoad could do the opposite. I don't expect it to be 100% accurate but more realistic than what we have it present. Unfortunately I'm only able to maintain 40+mph going downhill!!!

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    Jorrit Kortink

    I've looked through this thread but I can't seem to find a conclusive answer.
    I use the direct upload to Strava, when my file is on Strava I get a speed reading that is a full 10km/h at the same power as a friend of mine. Since I like to keep track of my distance ridden (even estimated) this bugs me a bit. Is there a solution to this or not?
    I've looked through the tcx file and it looks as though Garmin tries to do some calculations on speed and distance (Garmin activity extensions sound familiar to anyone?)

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    Kat Jennings

    Hi - is there any update on the virtual power being updated? My 'speed' and KMs on strava are quite high and I think inaccurately so. Like other riders I'm logging miles on the trainer as part of my targets so this is bugging me as my overall KMs for the year will be inflated. It seems to have come up a bit with a change of tire too - I had some graphene tyres that were not working at all well with the trainer and when I changed back to a regular tyre the speeds jumped up about 8km/h... I'm not currently riding in erg mode as I can't get my bkool trainer to synch.

  • Avatar
    Corey Croasdell

    @Kat Unfortunately, we don't have an update on VirtualSPeed just yet. At the moment we're focused on a few other major projects and haven't had time to focus on VirtualSpeed.

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    Razvan Catinas

    The distance reported on Strava is a big error (1 hour at avg power of 127W says 54.7km – so wrong!).
    If Zwift can estimate distance based on power, weight, wheel diameter, terrain (you can use flat all the time) even on ERG mode, is it so complicated to you?
    I do not need the speed, but I need the distance covered to be correct in Strava, otherwise why should I want to export on Strava?
    Please, do you have an update when this issue will be fixed?

  • Avatar
    Corey Croasdell

    @Razvan There are a few reasons behind the delay in VirtualSpeed.

    1) Even using a formula that takes power, weight, wheel diameter, and terrain into account will still only give you a rough estimate of your outdoor speed. There would still be a significant margin of error. Originally, what we had in mind was a super accurate algorithm that would allow us to calculated your outdoor speed based on your indoor power. To do this we would have to take a large number of other variables into account (wind drag, tire pressure, etc.) and then run some extensive testing and troubleshooting to make sure it was accurate - which would be quite a time extensive process.

    2) We think it's more useful to focus on power data instead of speed. We are huge proponents of power based training and even when read accurately, we don't think that tracking speed and distance are as effective as power, TSS, and IF when it comes to making you faster.

    That said, you do make a good point. Until we work out a way to implement our idea of VirtualSpeed It might be possible for us to make a physics based version that would at least be more accurate than the current system. We are still working our way though some really big projects, so unfortunately I still can't give you a solid answer on if or when we'll be able to roll out this feature. We will make sure to keep everyone updated on our progress though.

  • Avatar
    Nick Tode

    You guys are over thinking this. We don't need perfect. We need something that's within a mph or two estimating a flat road with no wind which means weight won't even matter much. I want my ride to reflect that at 200 watts for an hour the average size person goes 20mph on a normal bike not 40 and not 5 which is what we get today.

  • Avatar
    Corey Croasdell

    @Nick We hear you. We're actually reconsidering our plans for speed and distance. We'll keep you posted :)

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