Wildly inconsistent zero offset figures with Power2Max

I have a Power2Max NG Ego crankset which I’ve used for about 5 years mostly issue free. Recently, upon going back to indoor training, I started asking myself “why does this feel so hard” as is common.

This led to zeroing, which I honestly don’t do very often. I get huge swing in zero from about 500 to 1200 in the TR desktop app. I repeatedly zeroed about a dozen times and there doesn’t seem to be any obvious bell curve its more like a random number generator. I don’t seem to experience this when zeroing outdoors with the garmin head unit.

Has anyone had a similar experience or have suggestions? PM battery is about 65% and yes I’m unclipped with the freewheel stopped. Also, how substantial are these differences? What is 500 vs 1200 like in terms of watts at 90 rpm?

My P2max auto zeroes whenever you stop pedalling… i thought they all did. so maybe you are trying to zero something that is already zeroing itself?

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Whether it does or does not self-zero, I still question whether the results I’m getting when manually zeroing using the TR software are indicative of issues be they with the powermeter or the TR software.

I think this is the type of question best sent directly to support at TR & P2M.

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I’ve had 3-4 or P2Ms and they have all done this is as well. I haven’t noticed a large difference in the RPE regardless of what value it throws back.

I can’t prove it, but I know that P2M returns data differently than many power meters. For the same speed and effort in a ride/race, I will have consistently much much lower numbers than others who are essentially the same as me. I have sort of narrowed it down to how often the unit samples data. This brings the power average way down for stochastic efforts.

Often the numbers that are displayed after a “zero” don’t actually mean anything at all. I doubt it is giving you any information on the quality of the calibration.

P2M told me the calibration numbers are parts per million.
But my P2M usually only shifts by a few units at a time.

Solution: Don’t zero it with TR.

I asked the same question 4 years ago: Calibration/offset values varying a lot vs Garmin

I haven’t been bothered about it since then. I’ve never noticed a difference one way or the other so I think ignoring it is the right way to go.

It seems like you had a similar experience. What both of us experienced and which hasn’t been answered in either thread is:

  1. how significant is the value in terms of watts (i.e. should I care)
  2. if zeroed repeatedly why aren’t the resulting numbers more consistent

I know a zero is just a zero and there is no reason to “want” it to be in a certain range, but its unclear if the “true” zero is ~500 or ~1200 so how many times should I press the random number generator before I train?

The answer to how many times is ‘zero’.

Your manual zero is overwritten every time the pm auto zeros. Which is something like 3s after it detects no motion?

Are you using BT or ANT to communicate with TR? I noticed these huge swings in the zero offset number when using BT, but then when connecting with ANT it is consistently 72-74.