zpower vs. power meter


(Vince Kim) #1

i just ordered my first ever power meter. i’m curious to see how accurate (or not) zpower is with dumb trainer and speed sensor. i’m expecting my actual power to be a little lower than zpower but hopefully not too much. i don’t want to have to struggle with a C group ride lol.


(P MAC) #2

If you calibrated z power correctly then the figures shouldn’t be too far off. 

Which can’t be said for many z power users pushing out 6-7wkg on the KOM’s. 


(Shydn Crumph) #3

in my case zpower displayed 25% higher power level than my power meter.

(and yes, i used the trainer according to specs)


(P MAC) #4

My tacx vortex did the same thing. Went from an FTP of 320 to 280 watts using a Quarq DZero. Was gutted lol.


(Vince Kim) #5

first zwift ride with power meter yesterday and i think power went down about 15-20 watts. not a huge deal i guess. i’ll just have to adjust to my new power output. now i need to do an ftp test. ugh…


(Joe Daknis) #6

Sounds like you already have your answer.

In my case? zPower (w/ OLD cycleops fluid2 c. 2004 and Garmin Sensors)  was *low* - by ~ 37% (!!) vs. power readings from the Elite Direto I replaced my fluid trainer with. (and I have more than a year’s worth of data to prove it)

I consistently inflated tire to 100 psi and torqued the tension per cycleops’ spec.  

FTP went from 140W to 221W with the switch.  Needless to say, I cringe whenever I hear people talking about zPower giving them ‘optimistic’ readings.  Mine punished me, lol. 

It didn’t matter, as far as effective training goes - but try to race w/ a 37% power-to-weight disadvantage? Forget it.