Originally Posted by
njkayaker
You need to be specific about what point you are talking about. The top of the pedal or something else.
Talking about the top of the pedal (where the cleat attaches):
- The center of the pedal axis (axle) on the crank is going in a circle.
- The top of the pedal is a bit "higher" than the pedal axis.
- If the pedal is kept horizontal throughout the stroke, the distance between the center of the crank and the top of the pedal is shorter with the crank arms horizontal than when the crank arms are vertical.
- I think this means pedal stroke isn't circular (but not by much).
- It's not a symmetric shape (ellipses are symmetrical).
People don't keep the pedal in the same orientation (relative to the ground) through the stroke. But that shouldn't matter much. The only way the top of the pedal moves in a circle is if the pedal is always orthogonal to the crank arm throughout the stroke.
A > B > C
Ok, so I think I said something similar above, and I'm still firmly in the not a circle camp. But I had a couple of hours of riding time to think about it and yes, the pedal would track a circle if it was orthogonal to the crankarm at all times all the way around, but that is just a special case of keeping the stack from changing the overall distance from the center as the pedal spindle rotates (or rocks), as it travels around, which can be accomplished by locking the pedal from spinning in any position, no?