Originally Posted by
genejockey
This is exactly it. The center of the circle is the center of the circle, not the center of the BB spindle.
There it is. The path that the top of the pedal traverses is exactly the same as the path that the pedal spindle traverses, a circle, but the top-of-pedal circle is shifted upwards by the amount of the stack height.
Two circles of identical size, with one shifted upwards from the other.
/thread