Alas, I accidentally discarded the ramp test I did prior to this. I made it ten minutes in with one leg and my son was asking me what was wrong with my leg. At the time I was using both arms to help keep the revolutions steady.
Do you want to update FTP? No. Oops. Data gone.
Anyway, the attached graph shows me doing a little chunk of Pettit immediately afterwards. I changed gears a few times between mid and 1st.
There’s a definite drift between the two units as the power starts to climb. It’s easily outside of the claimed accuracy of both units. Now it’s time to find out if either are accurate.
I’ve been through Stages, Wahoo Kickers, Garmin Vector 2’s and Tacx Neo and the one things i have learnt is that you are never going to get readings that match up a, and any claims of 1% accuracy are total ^&%^&%^
Had kicker, FTP = 285, Vectors recording Same interval to another source … FTP = 268
Swapped to Tacx Neo, did a FTP test Vectors with claim 272, Neo 248
Just use on, stick to it and get on with training
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I agree with you for the most part.
I’ll crack on with the training and keep using what I have to measure power, for now. However, I will not accept that an inaccurate power meter is OK.
A power meter has one job to do. If it can’t do it, what’s the point? $800 for a carbon crank that weighs as much as the cheap aluminium one it replaced.
It seems strange to me that it’s commonly accepted in the cycling community that PM accuracy claims are mostly bogus.
I agree, there is a lot of hype around accuracy, but I don’t think it is as imortant as you think it is. As long as the power meter is consistant and gives you the same reading each time, does it mater ? if your power meter says 250 or 750, you are training to a percentage of that number, so it doesn’t mater what that number, if you only had one power meter and it was reporting 2000 watts as your ftp … you would train to percentages of that, you would be none the wiser, and it would make ZERO difference to your training
What difference does it make if the accuracy claims are bogus ? The single job of the power meter is to return a consistant measurement of power, so that you can have consistant training (and accurate based on a consistant measurement), the accuracy is regarded as less important, as to the most part … you aren’t comparing it to anything other that other reading from the same power meter.
That’s simply not the case in my situation.
I train and race outdoors with a power meter fitted to that bike. I mostly train indoors with another bike that has no power meter.
I get that I can train to my hearts content using just the indoor trainer and an app like TR. No problem there.
Trying to use that information as a guide to pacing, or anything else for that matter, outdoors on the other bike is a waste of time if the readings wander significantly.
What difference does it make if the accuracy claims are bogus? For starters that’s generally considered to be fraud and it interferes with training/racing for the reasons mentioned above.
Fair enough, if it was that important to you, I would use the same power meter inside and out, and I wouldn’t compare a single sided power meter, to a smart trainer (that doesn’t include a strain guage) measuring at different points in the drive train and expect exacting results
If you look for pedalmonkey (thats me) on the TT forum (uk) you will find that I made a very similar post (entitled Kicker vs Stages comparison), 2016 when I first got my kicker (had been using stages on dumb trainer)
Have a great day
My favourite comment.
“I’d probably also become disillusioned about training with power if I were using your equipment…”
Pretty funny.
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I’d also like to say, I was a more angry person back then 
… maybe it was my equipment that drove me to anti depressants
Sorry if i was a bit off … just realised that I have alread been through what you are going through … good luck, and hope you sort it out
I ended up with just one power meter, and only use it for TR or Zwift, do outside on feel only, but that’s not how it’s supposed to be. Literning to DC Rainmaker over the years, and it seems that if you have two SRM’s they will probably be slightly differnet. I’ve probably got to the point where I can’t worry about it any more
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You’re all good. I’m pretty cruisey and don’t view criticisms as a negative when I ask for advice.
I’d be interested to know why Andy and Co dislike the Stages so much? I haven’t finished reading the post yet, but I think it’s based on the one sided nature of the Stages unit?
Yes it was definatly the one sided thing, I found that it would give me a consistant FTP but my balance changed (I was never far out 54/46 if I rememmber rightly) but it would change to 50/50 / 40/60 for V02 \ threshold, and changed again as I got further through long intervals (I may not have discovered this until I got the vectors) so it wasn’t consistant over the range \ duration
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Thanks for that.
I’ll log a few more data sets using my left leg only and then continue my conversation with the Aus distributor. It’s an interesting one as it’s the same distributor for both the Stages and the Kickr.
They even tested the Kickr and gave me data files to show how perfect it was.
