TACX Neo Reading Low Watts?

Continuing the discussion from I'm either having a really bad day or my Tacx Neo is suddenly reading low:

I too have a discrepancy between my Tacx Neo Gen 1 and my Stages power meter. BTW, I also have a set of Garmin vector pedals which pretty much agrees with the Stages. I decided to do a 4 week FTP program via TACX. I had done a FTP using the Garmin vectors about 2 mos ago and came out with about 240w ftp. So I put in the TACX settings a FTP 241. I barely made it through the first workout and really flopped on the second workout. I was about a week past Covid so I thought it might be that. In my mind I figured that I could drop it 20w and do the workouts. The correction that I made was good, but I worked hard but could maintain my cadence through the workouts. One day I decided to check it with my Stages and there was between a 40-50w discrepancy with the TACX Neo on the low side. I have always figured that my Stages was not all that accurate, but it gave me a base to work with. I then came across this site: An interactive model-based calculator of cycling power vs. speed. It is basically a calculator for computing watts verse speed. I was shocked…my Stages was spot on and the TACX was reading about 40watts low. For example, I did a 5 minute segment at 231w. According the calculator, my speed should have been 21.89mph. My TacX showed 231w at 24.1mph. My Stages power meter indicated 294w. The calculator indicates that at 294.96w the speed for my settings was 24 mph. So I am not sure of the accuracy of the calculator…way beyond my brain capacity, but this was all very interesting.

Since you linked my thread, I started using powermatch to my pedals.

No idea if its been fixed or not. But the issue seems to be gone now either from changing fitness or its just gone. My pedals were dead for a couple weeks recently and just used trainer power and didn’t find it too hard.

I have had 2 tacx neo’s and stages left power meter on all my bikes. Stages has always read higher than tacx for me. I use the tacx power reading indoors and stages outdoors. My ftp is 25 watts different indoors to outdoors. I’ve always made the assumption that stages read high and tacx more likely accurate, but who knows. The total difference is due to the different measurement device, different location on the bike (tacx is after the chain loss), and I can do slightly more outdoors.

It took me awhile to figure this difference out and longer to hone in on the right delta. I had the same experience where I tried to use stages outdoor FTP on the indoor trainer and completely failed workouts.

Guess my point here is yeah don’t try to use the same FTP on different equipment. A lot of people have requested TR add a feature for multiple FTPs in some form. You can find the thread on this forum. Changing FTP constantly isn’t too annoying, but now it also messes with progression levels.

what? how does a stationary trainer go 24.1mph? virtual speed (which is about as BS as it gets)?

I don’t know if you can borrow some pedal based power meters, then you can triangulate a value. I don’t know what you can do about a Neo (1), though. It’s got to be long out of warranty by now.

FTP test (of choice) using trainer power, use trainer power to train… done!

Weird - my Tacx reads about 25W higher than my stages power meters (L/R) which I learned the hard way a few years ago. I spent the winter TR training using Tacx numbers, then paced myself outdoors using that FTP outside and promptly blew up.

I switched to power match inside and driving the workouts through my Stages meters, and things were much better afterwards. I’ll admit though that indoor on an erg is still tougher, without the little rests and better cooling you get outside even with a giant fan indoors, so I regularly hit somewhat higher Avg and NP outside than inside,

No idea which of the two is “correct:” or honestly whether either one is, but that really doesn’t matter. As long as whatever you use is consistent over time, you’ll get the desired training effect and it’ll show up in the only measure that counts - outdoor speed,

just remember to do a sanity check and then offset your targets if necessary anytime you change measuring devices!

A different turbo trainer for me (Elite Suito) but I find it was an OK match to the PM at a steady state cadence but with a constantly increasing cadence it lagged behind the power meter and often never caught up (particularly on short intervals) and could be significantly below. I was having trouble with my PM for a bit and powermatch was randomly dropping out and ERG was using the trainer. Thankfully I got to the bottom of the PM issue and I stopped paying attention to the Suito and could just use powermatch reading off the PM for one consistent figure.

Had a low reading Neo 2T since late 2019. Everybody tries to convince me neo is the right reading one :rofl: Meanwhile quarq, 4iiii, Vector 3s, P2max and now kickr bike all agree with each other and around 6-7% more on average than the 2T.