Dual recording power and Transparency

At 300w 3% difference would be 291w lets say ons a 3 or 5 sec alg. these numbers would be pretty close.


dont underestimate a 9 watt difference im using my P1 pedals for power (last race) they are approx 9 to 10 watts more than my neo; the race felt significantly easier and i had the energy to muster a decent sprint fine lines are the difference between a win or a loss


This can’t be overstated enough I reckon. One source reading -2% held up against another reading +2%. They’re both perfectly legitimate measurements in themselves, but they create a 4% difference - and we’re still no closer to knowing which one is actually the more accurate.


Reckon I should be able to pair up 2 or 3 power sources, and at any given moment Zwift should use whichever one is reporting the highest power. :smiley:

That’s without even starting to think about your new 10t cog, dirty chain, worn out bearings, etc.


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Just from the chain here are the quick losses that I could find estimates for:
12w clean chain
5w good chain
4w right length
3w cross chaining
2w chain tolerance
2w chain wear
1w deep clean
4-5w super lube

As always that is the responsibility of the rider I guess.

Yes, please.

If Zwift could support zwiftpower with more serverpower it could perhaps be switched on again?

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As seeing that in most races, I’m just trying to make it to the finish with the likes of Indoor Specialists, I’ll pick 300 watts over 291 watts EVERYTIME, if given the option. For me that would be 4.225 w/kg vs 4.099 w/kg, which looks to be just good enough to finish top 20 in most A races.

Personalty I think there is more to it than Server power. If you don’t have a secondary power meter you look like a cheat. That feel wrong.

Power meters all have aberration, so even on 1 source, you could have an over or under-read of ~0,5-3% depending on your meter. Dual power setup only shows that your primary source isn’t way off. Some wheel-on trainers have power est. instead of power meters, they are known for over-reading. My Elite Rampa ie did over-read by 15/20W. at 250W to my 4iiii power-meter, I now have a Direto II that is within ~3% of my 4iiii power meter.

I have seen people with a Vortex thinking they can hold 310W over 20min at a heart rate of 155bpm.
When in real life they struggle to ride (estimated by strava)150W at 150bpm.

I have ridden the same Zwift and IRL events as the person in this example.

What is suggesting is more for transparency, not for calling people cheats.
People who have a dual power setup could really benefit from the similarity score.
I love to know my numbers are real, this way there is less doubt.

That is not the the point Im trying to make.

Reasons for dual power for my are:

1.) Transparency in races to others (I Win/Lose transparant, not having Dual power isnt bad, having is just a plus)

2.1) Self control, are my numbers real? Self verification.

2.2) Calibrations alerts

Not having dual setup is just as looking like a cheat as riding with ZPower, no big deal.

First of all: Which protocol is the most accurate today or in other words which Powermeter unit is the most hightech? Cyclus2 or SRM i guess is still the line … and even here … I saw powermeters which show approx. 30 W lower over time because their strain gauge were less accurate (especially the case when heat or cold is involved - temperature drops/ups).
Pedals are different to crank spider measuring units. I’m pretty sure many Smarttrainers don’t show exact values by different temperature and higher wattage to each other. The point is: if you want it even more serious too much effort is involved to stabilize reliability.
Still the question of all question to this case is: Which is the most accurate powermeter?

I want a backup power source just so if one drops I don’t come to a standstill. Link my power meter and my trainer please - average then together if you want.

Double checking Powermeter will be fun read this:

Although manufacturers of bicycle power monitoring devices SRM and Power Tap (PT) claim accuracy to within 2.5%, there are limited scientific data available in support. The purpose of this investigation was to assess the accuracy of SRM and PT under different conditions. : First, 19 SRM were calibrated, raced for 11 months, and retested using a dynamic CALRIG (50-1000 W at 100 rpm). Second, using the same procedure, five PT were repeat tested on alternate days. Third, the most accurate SRM and PT were tested for the influence of cadence (60, 80, 100, 120 rpm), temperature (8 and 21 degrees C) and time (1 h at ~300 W) on accuracy. Finally, the same SRM and PT were downloaded and compared after random cadence and gear surges using the CALRIG and on a training ride. : The mean error scores for SRM and PT factory calibration over a range of 50 - 1000 W were 2.3 +/- 4.9% and -2.5 +/- 0.5%, respectively. A second set of trials provided stable results for 15 calibrated SRM after 11 months (-0.8 +/- 1.7%), and follow-up testing of all PT units confirmed these findings (-2.7 +/- 0.1%). Accuracy for SRM and PT was not largely influenced by time and cadence; however, power output readings were noticeably influenced by temperature (5.2% for SRM and 8.4% for PT). During field trials, SRM average and max power were 4.8% and 7.3% lower, respectively, compared with PT. : When operated according to manufacturers instructions, both SRM and PT offer the coach, athlete, and sport scientist the ability to accurately monitor power output in the lab and the field. Calibration procedures matching performance tests (duration, power, cadence, and temperature) are, however, advised as the error associated with each unit may vary.

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utter bollox

And what evidence do you have to back that up? Tests done by Zero Friction Cycling, formerly Friction Facts now owned by CeramicSpeed and others say that it is not “bollox”.

this is a massive can of worms the physics behind how a drive train operates is complex; your total watts in your list is large and can be interpreted differently by each individual that reads it. ceramaic speed are there to sell stuff so naturally they will spin it out to look good for them. general rule of thumb is a well looked after drive train should be 97 -98% effective, so for me with ftp of 250 should be seeing a loss of 5 to 7.5 watts tops; tbh i didnt read your post properly and a lot of those watt losses are duplicates of themselves. I added them all up assuming you meant 30 plus watts loss so apologies for that

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I don’t think that zwift should combine the power numbers from the two meters, but rather, allow you to specify one as the primary and one as the secondary “witness” PM for proofing the modulation of the primary.

But this would be really nice if they just incorporated the ability to record from two different sources so it’s all in one place