I “share” a pedal-based powermeter between my road bike and my spin bike. I performed an FTP test a few weeks ago on the spin bike but only just realized now that the crank lengths are slightly shorter (they are 170 but I calibrated the powermeter at 172.5 which is my road bike crank length).
FTP was calculated at 237 as a result of the test.
Am I correct in assuming that my FTP is actually slightly LOWER now that I know this error occurred? I’m assuming that it’s lower by a factor of 170/172.5 or 98.5% of the original.
This is a pretty insignificant difference (new FTP would be 233 based on this) but I just want to ensure I understand the difference.