I’ve been using PowerTap P1s for a couple of years and it’s always nagged at me that the reading changes depending on my position on the bike, and perhaps how I’m pedalling.
Has anyone nailed this down as to whether it’s a real phenomenon for a start, and then what the cause is?
I use a dumb trainer, the resistance is fixed. I have to change gear to increase or reduce resistance.
If I’m doing 90rpm and the power meter says 180W, I can shift to aero position - still doing 90rpm at the same resistance - yet the meter reading will drop to 165-170W.
So before anyone leaps in and says “it’s normal to lose 10W in aero”, I can’t be…If I have the same resistance and the same rpm, I must be outputting the same watts, right?
I think I get the same still upright, if I change the ‘feel’ of my pedalstroke to be more stompy I see less power. If I kick over the top more, a more circular feeling stroke, I see more watts…but again this is the same rpm at the same resistance…am I going mad?