Here's another topic that might be worth discussing. I've been communicating with my M1's former owner, Phil Plath, about something that has been bothering me from the very beginning. The issue is that my legs feel cramped on the M1, as if I can't extend them fully. Curiously, this only happens when I'm riding it. When I have it on the trainer, and I'm just spinning the pedals against no resistance, I don't feel this sensation at all. The strange thing is that Phil and I are exactly the same height and have the same leg length, so if the M1 was made to fit someone of his proportions, it should fit me as well. I think I've finally gotten to the bottom of it after watching one of Phil's videos in slow motion:
The most important frames are between the zero and three second marks. If you slow the video down to 1/4 speed, you can clearly see that Phil's foot at the bottom of the power stroke is at 90 degrees to his shin, exactly as it would be if he were standing upright on a flat surface. My style of pedaling looks very different. Under power, my tendency is to push the balls of my feet forward slightly, so that the angle between my foot and shin might be more like 100 degrees. Extending the foot in this way obviously lengthens the leg a bit, which accounts for the cramped feeling. When I deliberately pedal "flat footed" like Phil does, the problem never materializes.
Yesterday I spoke with a couple of bike fit specialists and asked them about this. I was particularly curious to know why they insist on having the balls of the feet extended a bit when determining seat height on a DF, which is almost certainly why I formed the habit of riding this way. Neither of them could give a good answer. All they could say is that this is how they'd been taught to do it. Neither of them knew of any reason why it would be a bad thing to keep your foot/shin angle at 90 degrees. In fact, one of them mentioned that his preferred method is to observe how a particular rider naturally positions his feet and use that as the starting point. I asked him if he saw someone holding his feet at 90 degrees, would he try to correct it? He said that he'd observe the rider pedal for a while, and if it wasn't causing him any problems, there would be no need to change his foot/shin angle.
Unfortunately the BB on my M1 is fixed in place. To move it forward, I would have to bring it to someone used to working with carbon fiber and have him lengthen the slot the bottom bracket fits into, as shown in the photo below:
But before I do anything that drastic, I'm going to try to get used to holding my feet the way Phil does.