Just back from my first ride on my second bike fitted with Rotor 3DF Type S Power2Max - same result 47% L / 53% R

I know what a Wattbike is. I was surprised you said you measured P2M and Wattbike data together, I thought perhaps you had some funky custom arrangement, but now it's clear that's not what you meant. i.e. you are quoting values from three meters on different bikes measuring power balance.


Those are not the only two possibilities.

The P2M and Wattbike are measuring one thing, the Rotor is measuring something quite different. While they each use the term "Power Balance", they are not the same measurement.

Hence if you directly compare Rotor's data with either the Wattbike or P2M, then any differences may be a multitude of things.

The fact that your P2M and Wattbike report different power balance is of more concern suggesting one or both are wrong since they use the same means of power balance measurement.

You have no way of knowing if your Rotor is or isn't correct.

Then ANT+ shouldn't allow both to use the term "Power Balance"!

From what you've said, Power2Max/Wattbike could produced a more accurate "Power Balance" than Rotor/Vector!?

They are aware of it but I don't know what they are proposing to do about it, if anything.


One method is not intrinsically more accurate than another. They are just measuring different things.

For instance say you had a meter of each type and they were each very accurate (e.g. within 0.1%). Despite that, each can still provide quite different power balance values, even to the extent that one might indicate right side dominance, while the other indicates left side dominance. Or one indicates symmetry while the other suggests an asymmetry.

How you decide to interpret such information, let alone act upon it, needs to consider what is actually being measured.

This is partly why PB values are, for the moment at least, red herrings.