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Tacx NEO 2 power accuracy

Monadic cyclist
over 3 years ago

Hi guys,

My Tacx NEO 2 shows lower power compared to Assioma duo power meter. I tested my FTP on Zwift, and the results were as below.

Tacx NEO 2: 190W

Assioma duo: 220W

It seems Tacx NEO 2 outputs 10% lower power constantly. Is there any way to fix this?

  • 0 over 3 years ago in reply to Monadic cyclist

    okie. when You pedaled with only 1 leg, @this 80w level the difference was low (3w and 5w apprx) so with 2 legs must be the same at this power too (try it), if it is much more than problem is your position on the bike. The question is what will happen at 120w or on higher  (of course, if You are a lighter rider it will be tough to pedal with one leg). So if the difference is getting bigger and bigger as the power is increasing that could be a wrong slope calibration in Neo2. the 10kg a bit low (in my eyes) for validating pedal's slope value, this is why i suggested at least 20kg. but with the 10kg You can validate the balance, if both side shows the same % with this weight then both pedals are the same so 50:50 (just we dont know the exact slope accuracy, always the heavier weight can give you more accurate data). 

    Okie, try to lower it and practice (You can do it in ERG mode too or in SIM on flats with small ring front and easy gear to get that 80-100-120w range which is "comfy" with one leg.)

  • 0 over 3 years ago in reply to Luko79

    I tested again with 14.6kg weight (that's all I have). Right measured it as 14.62, left as 14.6. I think I can assume my Assioma power is correct. The cause of power diff could be either Tacx neo 2 calibration or my pedaling inefficient pedaling. Anyway, I got good understanding about the issue. Thank you very much for your help and I will report here if I find more details!

  • 0 over 3 years ago in reply to Monadic cyclist

    Yes, those numbers are very close to each other so good. yep, this 2 things. Okie, i will be here ! :D

  • +1 over 3 years ago

    I've had the original Neo, bought in 2015, replaced under warranty in 2017 with the facelift model and that replaced under warranty in 2019 with a Neo 2. I also have Assioma Duo pedals.

    By perceived effort and heart rate vs power at steady state (e.g. 200W for an hour)  the two Neo 1s matched for power very well, if not perfectly. I was able to compare the second unit with my pedals and the data was very close, usually bouncing +/- 1% within each other. This is the sort of result you see when Shane Miller performs power comparisons.

    With my Neo 2 I find the power is under reported by 7-8% at all power levels from 100W warm up to 1,000W sprint. I've performed static calibration on the pedals and they are correct. Matching the pedals to my second Neo (which matched the first Neo) is further validation of the pedals.

    The Neo 2 is flat out wrong. I'm no longer on Facebook, but this was discussed there with many people having the same complaint. As far as I know the only fix is replacement., but it's now over five years since my original purchase so I'm just living with it and adjusting training accordingly.

       

  • 0 over 3 years ago in reply to eezytiger

    Thanks for the detailed explanation. That exactly matches my observation. Probably some unfortunate lots got wrong calibration. I've decided to use only Assioma Duo as power source in Zwift. Will check warranty but likely I live with it.

  • 0 over 3 years ago in reply to Monadic cyclist

    The original Neo2 is a problematic model, now i found 2 units which overreport the power and these are under investigation. So as Tim wrote, if the warranty is out now then use the pedals as primary power source and the trainer as a controllable (in Zwift), if it is still in it (it has 24months i suppose) should raise a ticket and send back as late as possible during the winter.

  • 0 over 3 years ago

    Did you already find a solution? Fear I am facing the same issue

  • 0 over 3 years ago

    Did you find a solution already? Fear I am facing the same issue with my 4iii power meter

  • 0 over 3 years ago in reply to Monadic cyclist

    Mine is the same, Tacx neo 2t always felt it read low compared to my friends and their efforts outside compared to mine. I have assioma uno and it reads around 10% higher which feels accurate when I compare to friends as mentioned above.  

  • 0 over 3 years ago in reply to ckoutdoorfitness

    I have the same issue: the Tacx Neo 2T underreports power by at least 10% compared to Assioma DUO, Wattbike (ncluding various max ramp & 20mins FTP tests) as well as real life. I don't need further testing of my Tacx, but correct power reporting would be nice. Is there a solution?