I’ve read articles about this topic from the fisiological point of view, , but I don’t think I have read about the technical aspect.
From RPE I can give an estimate of 15/20 watts difference outside/inside, on a steady 8/9% climb. (that is 8/10% on my FTP).
But then hey, I have Favero Assioma pedals on the real bike, measurement is on the hub (after the hub?) when inside. Inbetween there’s cranks, crankset, chain, sprockets, hub…
Is there a way to estimate power losses between the ends of the power transmission process?
Yes. It’s been measured and characterized many times and depends on things like ring/cog size, chain lube, jocky wheel size… Try googling “bicycle drivetrain efficiency” and you’ll find many articles on it. Of course there will be many marketing pieces trying to sell improvements, so view these with appropriate skepticism.
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Could you just put the Assioma pedals on your indoor bike and then compare live power from them vs power reading from trainer?
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The Assiomas and the trainer both provide measurements of power that are accurate within 1 or 2 percent. If you have single-side power measurement like the Assioma Uno, there is error due to the necessarily simplistic way of estimating the contribution of the other side. Power train losses should be on the order of 5 percent, so the noise is potentially pretty large compared to the signal about drive train losses.
I put my Assioma pedals on my indoor trainer and saw a large difference in the wrong direction for drive train losses. Fortunately my new gravel bike had a SRAM Qarq spider power meter and happened to arrive that week. After (buying a new scale and performing a static calibration, the Assiomas matched the SRAM very closely, so I assume those two are both accurate. Putting the pedals on my indoor trainer showed that it read several percent high. The manufacturer provided a fix to correctly calibrate the indoor bike simulator. But with 2 power meters that disagree, there was no way to identify which one (if either) is most likely to be correct.
The person with one clock always knows what time it is, the person with two clocks is never sure (at least before GPS and internet time servers).
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there’s no correct measure, you just have to be coherent
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genius lies in simplicity, thank you
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