Fwiw….

Some folks have the roadie habit of backpedalling at stops to align the crank to start again. Cannot do that in an aero test with a Quarq. That engages the on the fly zero at that time. Apparently this can be disabled via the app so only GPS manual zero is used.

If unlucky enough it is possible to do this and barely not violate the zeroing error check and your foot is light enough on the pedal and suddenly you’re at 25mph and reading 100w.

I had a support ticket with Quarq blame what I saw on a ride with that and also the battery cage spider needing the legs bent more. That all resolved that.

I thought you could change the slope in their app? At least they claim so:
https://www.power2max.com/en/2017/07/power2max-app/


I have the 1st generation P2M (going on 10 years and likely 100,000+ km in all kinds of weather!) and can static torque test it, but not change the slope. Seems like with at least NG and NGeco you should be able to do that so you have whatever you need on that front.

This is what pissed me off this week.

You can set a %. So you can say "report 98%". But you can't measure off a hanging weight so not sure what you would scale this off

My conversation with them went like this

me : hi, can i do a static torque test ?
them: you don't want to do that, here is an article on how we calibrate
me: fine, however it is reading 10watts higher than my other PMs and I'd like to get to the bottom of it
them : your other PMs are probably wrong but if you want you can knocks 10 watts off by using a %.

I was told I could pay 50Euro to be able to display a torque value on wahoo, not a garmin but I would be disappointed with it.....so not sure what to think.

In the paperwork with my P2M came a slope value that defined how much each ZO unit was in Nm. Using that you could do a static calibration just using the ZO value with and without applied weight (like you can on e.g. SRM and Quarq). I can't tell you if it works like that on newer units, but that's how it works on mine.

Yes I remember the good old days with my Quarq.

Today I do a static calib, get a 47. Hang a weight, do a calib, get an error :-)

I'd be more than happy to be wrong

Had no idea we could do this. Three Wahoo kicker and all three read 10 watts higher than my P2M. Explains my faster bike splits on lower wattage. I'll have to check into it.

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http://www.sfuelsgolonger.com

You need smaller weights so you can slowly build up the torque to trick it ;p

Does your device auto-zero when you don't pedal ?

Yes

I have the same setup

Tacx Flux and Assioma, both single and double, I also have a Rotor INpower and a Quarq and a Stages

I dual record most of my races on Zwift and have an extensive log of how different power meters compare.

All of my pedal and crank power meters are within +/- 2%. You get more variation at peak power, +/- 10% for 1s peak, Assioma and Rotor seems to read highest. however, after about 15s differences are minimal

This brings me to the Tacx Flux. It doesn't actually have a power meter in it, it is a calculated power based on the power input to the magnets, Tacx and Wahoo use this mechanism, while Elite trainers actually contain a strain guage. The Tacx It is incredibly sensitive to when you calibrate, It needs a good 20min warm up before you calibrate, otherwise you get odd readings. Also, below 150w the Tacx reads significantly higher than Assioma, 180-300w it is pretty much bang on, 300w+ the assiomas read higher.

In a typical Zwift race, like a time trial, where I am averaging around 340w the Tacx is about 3-4% down on the Assioma, however, a newly waxed chain and a squirt of silicon lube on the belt on the Tacx brings it down to about 1% lower

Spot on. In addition to my Tacx Flux, I have a Tacx Neo 2T, which is supposed to be one of the best trainers on the market. When I first had it the accuracy was within 1% of my assiomas; all of the reviews raved about it. However, over the course of 2 years it has gradually got less and less accurate, currently it reads 6-7% below my Assiomas (Uno and Duo), and Rotor and Quarq. As there is no way to calibrate a Neo 2T I am stuck. Therefore when I race on Zwift and need to dual record I am back to my Flux as it is generally pretty close, as long as I warm it up properly and keep it well lubed.

Lots of people race on Zwift with their Power Meters as primary. Lots of people on this thread saying the same, ride indoors on same PM as you ride outdoors, I get it..... however, if you are close to winning races, then anyone who races with PM as primary is immediately suspected by their competitors, it's a really simple job to add 10mm to your crank length with an Assioma or Garmin Vector. You can change the slope on a Rotor, I guess you can do something to a Stages or Quarq. However, its much more difficult to frig the readings on a trainer.

Agreed. I have my kickr connected to TR and that's it. I use the numbers from my single Favero to Garmin 830 because that's what I will be racing with. Usually the kickr and favero are about 20 watts off and I calibrate every session.

The attached screenshot shows a dual recording last night with the Tacx Flux connected to Zwift and Assioma Duo connected to my Garmin. The chain was newly waxed and trainer recently serviced.

Over 20mins the difference is just 2% which is about right for drivetrain loss, however, short hard intervals of 1 minute or less the Tacx reads in excess of 6% low. This is fine for most people most of the time, but a disaster if you are e-racing and contesting the sprints