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Make speed calculation in relation to power more realistic

The calculated speed in relation to the power output has become very unrealistic, very close to Zwift "speed" now. I had a ride on Coastal Loop recently, averaging 23.6 mph with 200W average power (riding solo, not in a pace group). The same type of ride used to average around 21mph in indieVelo past winter. Please make the speed calculation more realistic, so the accumulated indoor training miles/kms would be somewhat accurate.

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David B. shared this idea  ·   ·  Report…  ·  Admin →
Declined  ·  AdminGeorge Gilbert (Admin, TrainingPeaks) responded  · 

Many thanks for your suggestion and support for TrainingPeaks Virtual.

Note that none of the physics algorithms have changed since indieVelo - it's exactly the same code. Both indieVelo and TrainingPeaks Virtual use a pure physics algorithm (F = ma) to calculate speed from power and extensive testing has shown that the speeds in indieVelo / TrainingPeaks Virtual match those in real life when comparing other factors like with like (e.g. CdA, Crr, wind speed / direction etc).

The most likely cause for any discrepancy you are seeing is a difference in CdA or Crr between the two.

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  • Mark commented  ·   ·  Report

    I have to agree that your speed calculation is off. I know in the real world that at 160 watts I am not doing 21 mph. more like 17-18 mph.

  • David B. commented  ·   ·  Report

    @Tim and @Pugnator Montum, I've been riding for some time now on modern road bikes and calibrated power meters. It would be almost impossible to achieve over 23mph with 200W power output on a flat road in a real-world environment (even on a road bike with the latest aero gains). This link has a calculating formula with CdA and Crr, check how much the CdA needs to be reduced to achieve 23.6mph with 200w, https://www.gribble.org/cycling/power_v_speed.html

  • Tim commented  ·   ·  Report

    Seems about right that 200W would be about 23.6 mph.

  • David B. commented  ·   ·  Report

    Thanks for your reply, George. I didn't imply that code has changed in TP Virtual, as I still use the indieVelo version of the app. But something has changed since February, as the calculated speed has increased considerably.
    Would it be possible to add an option in the profile to specify how aero the rider is which could alter the CdA?

  • Pugnator Montum commented  ·   ·  Report

    Hmm, is it? If I do a flat TT on a road bike at around 200W (I'm not fast) then just over 23mph is expected. (on a still day with no traffic)