OK, thanks. I think crank arm length is one of those things that can fit a formula, but there are plenty of people who lie outside the norm. I'm one of them. I have short, stubby, but strong legs that don't like spinning very fast. So even though the formula says I should be at around 145-150mm, I absolutely hate that length. I just feel like I can't get any leverage.

Like I said, I have one bike with 150s now. I took it for a ride yesterday on a route I ride pretty regularly, at least the first 10 miles out and the same 10 miles back, I ride pretty regularly. So I know this route, and I know roughly how fast I should be on this route. My normal time on that 10 miles is right around 30-35 minutes, depending primarily on wind conditions. Yesterday, I was 40+ minutes.

The problem is that at a cadence that's comfortable, I don't have the leverage to maintain any speed. So to go faster, I have to pedal faster, but I can't maintain that faster cadence.

Now, my Shiv came with 165s. I want to try 160s with it, but I'm far more comfortable with the 165s than I am with the 150s. I can spin a little slower and just use power to maintain a speed.

So what I'm getting at is that I think you need to determine if you are more comfortable spinning faster or grinding slower. Then you can dial in arm length and chainrings from there.