Just wondering has anyone changed from their power on their smart turbo to stages left crank. I see a fair difference in lower number but not as much as the number go up.
Any single-sided power meter is going to have discrepancies due to L/R imbalance.
For those who are left leg dominant, the left-only PM will read higher, and for those who are right leg dominant, lower.
I’ve never bothered checking L/R balance at different zones, but that’s an interesting thing that I may pay more attention to now. I would guess that it does not stay consistent from zone to zone, which further explains your non-linear discrepancy.
Also recognize that the claimed power accuracy can and does vary from trainer to power meter:
- Novo is listed within 5% accuracy.
- Stages is listed as +/- 1.5% accuracy.
That assumes proper use and calibration or zero offset at a minimum, and that the devices actually meet those standards. Then consider that you are measuring different points in the power delivery system, so you have plenty of variables (along with the potential for leg imbalance) that can lead to very different values.
Sadly, this whole “power” world is far from simple and direct.
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It’s good that the most important numbers are in sync. It wouldn’t matter that much if 100 watts was 10% off.
Also, try getting the trainer warmed up for 10-15 minutes, then do a calibration/zero offset on both trainer and Stages, and then check them against each other.
I just got started with using a Stages and I had a newb incident. I tried to do an outdoor FTP test since I had only ever done one indoors on my Tacx trainer. Well, I forgot to calibrate the Stages after 15 minutes of riding and the colder outdoor temperature made a huge difference in power. My FTP test was a total failure and 50-60 watts below normal!
Yeah, I was tipped off to maybe leave the bike sitting outside for 15 mins before going out and then calibrating it. Didn’t realise it would be so far out. Do you find a difference in inside FTP and outside FTP or have you done it yet?
I haven’t done a good outside test yet. I do seem to be putting down numbers that sound reasonable though.
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Unlike most meters on the market, which require constant and religious manual zero resetting, the Stages Power meter has an Automatic Temperature Compensation function, which allows it to Zero Reset itself when the on-board thermistor thermometer senses an environmental temperature change.
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The Stages manual says that and it also says to calibrate before every ride.
Ambient temperature shifts can also affect the zero offset to some extent. To ensure maximum accuracy it is advisable to manually calibrate the zero offset before each ride. The power meter utilizes automatic temperature sensors to compensate for temperature changes that take place during the ride. This is done automatically while you ride and you need not take any further steps to calibrate the sensor during the ride.