Sure, but if racing well is your goal, the super strong 180 lb guy who puts out a lot more watts than the 140 lb guy can still get his butt kicked on the flats, hills, or whereever by the 140 lb guy.

Relative power is way more important than absolute power.
And the king of all numbers for tri biking is the power-to-drag ratio.

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Can you explain, in detail, this fallacy?

Why is accuracy important? Important to predict how well you do compared to others? Or important to base of your training plan?

I always thought that consistency is all you need to train 'well'. So excuse my ignorance, but I'm trying to understand.

I got them a month after they came out and they always within a few watts of CT and quarqs (I sold the quarqs long time ago tho)

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The entire event (IM) is like "death by 1000 cuts" and the best race is minimizing all those cuts and losing less blood than the other guy. - Dev

This

In a 10 miler u might make the skinnier guy hurt but most races are a lot longer than 10 miles and usually big guys are great for drafting after u cover their first big acceleration.

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The entire event (IM) is like "death by 1000 cuts" and the best race is minimizing all those cuts and losing less blood than the other guy. - Dev

I have both p1 and power2max ng and power2max reads 4w higher than p1. Before I had a power2max classic and that one was about 2w plus/minus don't remember which.

With regards to the P1's, I don't doubt their accuracy, I doubt their overall reliability.

Me too :-)

Better the tile than your toe, eh?

My power2max was reading 20-25 watts low as well. Low compared to other meters. The p2m was consistent though. I decided to buy the new NG and see how it goes and I can use it in all three of my bikes (BB86)

I did not patch it for a long time, until my labs starting to dig it larger :)

The fallacy is that body size (as indicated by mass) does not influence the energy cost of cycling on level terrain.

The reality is that it does, by impacting 1) aerodynamic drag, 2) rolling resistance, and 3) inertia (when speed is not constant).

People buy PMs based on features, and that's a mistake. Being able to check the accuracy of your PM is like having the 9 key on a calculator. It's not a feature, it's a key.

Why is there an assumption that a static torque check will verify every calibration?

Has anyone ever put a Quarq or SRM on a dyno to see if their static calibration is in fact correct?

I have dealt with rotary torque cells that cannot be calibrated by hanging weights alone.

Hmmm. Why are you assuming that we assume that a static torque check verifies every calibration? A correct static reading of torque is a necessary but not sufficient condition for accuracy.

Usually I keep track of 2 important aspects in cycling:
1) 20mins all out test (indoor + outdoor)
2) 20mins all out test on a hill of 5-7% grade

Looking at both results, I can understand very well where I am at, every season.
for the first test, i pay attention only at the average power.
for the second test, I pay attention to the VAM which correlate somehow the average power to my body weight.
you can't neglect your body weight in assessing your fitness level.

regarding powermeters accuracy/precision:
I have a Quarq and my wife has P2max
we went to test our power in a lab where we could calibrate our bikes (powermeters) to a common smart trainer.
Her P2max was about 25W lower for the whole curve 100-400W, linearly, compared to the common trainer.

We were very surprised and so we wanted to replicate it outside just roughly. we went side to side on a hill, she is 1kg more than me (let's say identical), same Cervelo S3, both 2 waterbottles, and we climbed at the same speed. 20-25W difference confirmed.

just to let you know you should never rely on web calculations (on your final bike split) or comparison between 2 cyclist with different powermeters (even the same model can give you different statistics!).

I'm not trolling, I'm genuinely curious. I understand your thinking now.

Yes. In fact, I am even last author on a peer-reviewed paper describing the results of one of many such comparisons that I have made: https://www.academia.edu/...mech_1998_14_276-291

There are other peer-reviewed papers performing similar tests.

Although static testing won't reveal all measurement errors (witness the torque spikes generated by the Quarq described here: http://www.trainingandracingwithapowermeter.com/...r-type-from.html?m=1), it is definitely the first place to start.

(Note that back in 1999 I actually relied on a dynamic test of my original PowerTap hub, describing/attempting a static check only as a backup: https://groups.google.com/...mndbKeg/fYmeQBa4ksUJ)

Thank you very much :)

almost 2yrs and going strong; I even scraped the bottom of the pedals doing crits and it wasn't a problem at all.

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The entire event (IM) is like "death by 1000 cuts" and the best race is minimizing all those cuts and losing less blood than the other guy. - Dev

The AIS has published a number of studies comparing the outputs of SRMs, PTs, etc. with dynamic calibrations, which I'm sure you can find in a web search.

Also, take a look at a typical crank torque plot, and you'll easily see that the vast majority of the torque is applied through a fairly narrow range, so checking the torque output in that same area is going to result in a pretty good idea of how well it will be able to measure the power output of a human cyclist. Once you have that, measuring average crank rotational velocity is fairly trivial, and those are the 2 inputs to calculate power.

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http://bikeblather.blogspot.com/

Exactly...to get my Polar PMs reading properly, all I needed was an accurate chain mass measurement (and a "good" setup) ;-)

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http://bikeblather.blogspot.com/

Thank you

I have no disagreement with your statement above, and I believe I understand your point properly.

However, I thought what people were saying when they said "as long as it's consistent" was the power meter needed to give the same reading (even if off by a few points from the true number) consistently in order to be useful as a tool for training. I never read this statement to imply that body size did not matter.

Would you agree or disagree that a consistent powermeter was the most important factor when using it as a training tool for the average cyclist? Or does it also have to be accurate?

Relatively trivial but not entirely. We both know of certain PMs whose cadence measurements can be noisy in certain situations. Sometimes I think manufacturers were too fast in moving away from magnets and reed switches.