New power meter. New FTP test?

Hey ya’ll,

So I have a Dura Ace 9100-p crank based power meter. It’s crap. Everything I’ve read about these says they suck and they are not accurate. Particularly the drive side crank is poorly designed and is really inaccurate. This power meter came with my bike and before I looked into them I did my FTP Field test using this power meter. After analyzing my power on about 10 rides I’ve noticed that the power meter is pretty consistently reading around 60L/40R% . I’m pretty sure I’m not THAT imbalanced, coming from a fixed gar background I think I have a pretty smooth pedal stroke and a lot of people on the interwebs have said this is due to the design of the right crank arm on this power meter. With all that said, I’m selling this garbage power meter and already have a pair of Faveros Assiamo pedals to replace it. My question is, when should I redo my FTP field test? I’m going to continue to use the Dura Ace for my Zone 2 endurance ride tomorrow, then I have a rest day on Thursday and a 2.5 hour sweet spot group ride on Friday. Should I swap out the sweet spot group ride on Friday for a FTP test or should I swap Saturday’s 2 hour Zone 2 ride for Friday’s sweet spot ride and FTP test Saturady? Please help!!! I’m lost. I know we’re not supposed to test that often but I also know that my zones will change a fair amount switching power meters.

When I changed to assiomas from a quarq, I did a ride or two with both installed and compared the data on DCAnalyzer. They were super close, within 5-10w avg of each other and similar enough I didn’t re-test. For me 10-15w variance on a test could be the difference of the weather/temps, hydration, or even how stressed I am… I felt it was within the normal margins of error inherent to being an imprecise animated sack of meat.

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I’d try what @chad did first then decide what to do. I went the other direction, Assioma to Quarq, with very similar results so I did not re-test. Easiest way might be an indoor ride where Zwift, TrainerRoad, Sufferfest, etc. captures data from one power meter and a head unit captures data from the other power meter. If you have two head units you could go outside to capture the data instead. Probably use the DA power meter to do the workout, whether indoors or outdoors, since that’s the measuring device you’ve been using so far.

If you were going to retest to set zones, what might your PMC look like in the near future? Can’t imagine you’d want to test when your TSB is -20 vs waiting a week when it might be -5 (or higher).

Hi @jeremiah.ho - I think you are ‘in the ballpark’ so go with that and FtFP in the meantime. Adjust per the suggestions above.

As for when to test again - what plan are you on, what are you training for?

Thanks for the feedback, I think I will hold off on retesting until my next scheduled test.

What is PMC and TSB? Sorry, I’m new to all of this!

Hey Frank,

I’m on the 18 week sweet spot training plan. I’m not 100% sure what I’m training for yet. I want to do my first bike race this spring and would like to do an interval plan after I finish the 18 week. I figured the 18 week plan would be a good way to establish a strong base and then the interval plan would be good to get into race shape. When work restarts for me and once I figure out which race I want to do, I plan to hire a Fascat coach as well to really dial in the plan.

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PMC = performance manager chart
TSB = Training stress balance

Here is a great video that will help you understand the basics of the PMC:

Then, if you want to learn all the nitty gritty on the PMC and how @FRANK was a beta tester for it when it was being developed… check out this blog post:

Really great read and there are explanation of all the terms you’d ever want to know at the bottom of the article!