Virtual power vs power meter


as has been posted before by others I experienced the virtual power of my Elite Arion Mag Rollers to be way off compared to my power meter. I realised that during the last weeks while the power meter bike was not available.

Wouldn’t it be possible to provide users with a trainerroad ramp test with which we could calibrate the virtual power based on the input of our power meter? This would also eliminate the difference of tire choice and pressure. Possibly we could upload our virtual power curve so other users, which do not have a power meter, could choose from based on their bike setup?!

I think this is not the most important change in the software but it would be a nice one. Or maybe this is just me geeking out while staring 1,5h onto my front wheel :grin:


Not a bad idea but sadly you cannot compare one trainer with another even if they are the same model.

I have a tacx and a wahoo turbo and friends with the same report vastly different power discrepancies.

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I think every Roller or trainer has a power curve (Watts vs speed). This is the amount of watts needed to produce a certain amount of speed on that specific roller.

The difference between setups is than the bike, the tire, tire pressure, different drum sizes, weight of the rider etc. ! And if you compare between different training SW it might be that they use different power curves. So to me it makes perfect sense that the same trainer or roller produces different results in different setups!

That’s why I thought about producing my own power curve and using that in the trainerroad SW!

You get a hint of the complexity to prduce such a power curve if you look at the disclaimer on the watts chart from Kreitler (


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This is not that hard to do, just a scatter plot of power vs speed. In order to clean the data up, you would look at using several training sessions covering the full range of speeds, with many minutes in each interval, and then bin the data into speed segments, calculating the average power for each bin of speed. This is assuming you have on bike power measuring kit like cranks/pedals/hub.

Pretty simple analysis really. Whether its worth the time spent on it is another question entirely…probably not. If you have a power meter, do you care what the actual speed of the rear wheel is? As long as its in the ball park, ie around 80W for the lowest gear, I’d suggest that the exact power curve for a given speed doesn’t matter. For me and my Kreitler 2.25 inch, the initial low speed resistance is roughly perfect for a decent session.

Maybe more relevant is to understand where your FTP heart rate is, which you can get from the website and analysis of HR vs power. Then you can use HR in place of power, if your power meter breaks. You can see from beneath that around 90% of my MHR is where my power curve starts going wonky. Thats basically my FTP HR. Otherwise, the relationship is nice and linear, and you can pull different HR values for different target watts.

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Sorry, didn’t check the forum in some time!

But this calculation is great and yes it shows exactly where the upper level is. Will check and calculate a similar graph

Thanks for the input!