After buying a Tacx Neo that put me at 4 power measurement devices in my household. Since I got the Direto in February, it was a tad high but I didn't worry too much about it; my power was good on the road too. What I can do against my peers in group rides is maybe the best its ever been.
I use the CX bike on the Direto that has a Stages and they were close; within 5 watts or so. However, after getting my Neo this week it was noticeably low. So I ran some tests in a wattage comparison app and using 215 watts as a low base its close to this:
Neo = 215w (just purchased)
Vectors = 218w (used outdoors)
Stages = 230w (used on Direto)
Direto = 235w (used indoors
)
Is this important? Yes and No; on the high end it puts me at 4.3 w/kg ftp, on the low end 4 w/kg. With State TT's 7 weeks away the former was giving the hope I had a chance to stand on top of the podium (it depends who shows, as always). For other races, I'd gladly trade in that .3 w/kg for legit bike handling skills (but that's for another post). Anyway, on to finding what's accurate;
After researching the best way to find a which one is accurate, I decided on the
Vector Power Meter Advanced Torque Test below. My other option was to have someone with an SRM try out the Smart Trainers (which maybe I'll still do).
I followed the test protocols, and like any great mathematician, I showed my work:
Mass (kg) 29.4 lb = 13.33562 kg
Gravity = 9.81
Length (m) 170mm = .170m
Mass * Gravity * Length =
22.239813474 (expected result)
Left test =
22.22, 22.22, 22.25 (22.23 avg) Spot on!
Right test =
22.04, 21.91, 22.08 (22.01 avg) Close Enough?
After that I'm more or less happy with my Vectors; I believe that should put me within 1% on the right (I used an online calculator, got lazy)!
Tough pill to swallow, but I suck again. The good thing is I now have a baseline and I believe the Tacx Neo is spot on as well and the drive train contributes to the small loss. As for the Direto that's going to my wife, which the extra watts may help if we ride together in Zwift (I'll probably put in a ticket to Elite).