Originally Posted by Divebrian

For me personally, I found this to be incorrect. Granted, I'm not your average cyclist and at 6' and 235 lbs, I'm built more like an NFL linebacker. I recently went down to 165 cranks and both my road and track bikes, my gearing stayed the same and my speed went up. I attribute this to a few different factors of power delivery, comfort and aero gains. There is nothing aero about me, but stick with me and I'll explain. Every time I have gone for a bike fitting, they have done things by numbers, angles, flatness of back, etc to give me the correct position. That position was my optimal position in the fitting studio, but didn't translate to real world. In the real world, it led to a very upright position that killed aerodynamics. Since I have a very large chest and wide shoulders, with longer cranks, my knees were hitting my chest, which caused me to open up my hips to give my knees room to go to the side of my chest, which then meant my knees now hit the inside of my elbows, so I flared out my elbows. To keep my knees and elbows in, I adopted a more upright riding style to get my chest further away from the top of my knees. When I went to shorter cranks, my knees didn't come up as high, so they no longer crashed into my chest. This meant that I could keep my knees in, which in turn brought my elbows back in and allowed me to maintain a lower riding position. With the shorter cranks, it allowed me to keep a lower position with my knees in and elbows tucked, knees in gave me a better power delivery and not smacking myself in the chest with my knees allows me to be more comfortable, which means I can maintain that position and power output for longer periods of time. As an extra benefit, I picked up a few more rpm's, which coupled with better aero properties and power delivery, allows me to maintain a higher speed for a longer period of time.