Originally Posted by rmwun54
You will sit lower on the bike, you will lose the ease of spinning a smaller crank will give you. You will have readjust the way you sit on the bike (more towards the rear).
Actually, if you make the right adjustments you will sit slighly forward and higher than with your previous crank.
The idea of moving higher and forward (but same total distance to the BB as previous seat position.) is to reduce the amount of knee bending that would normnally happen with a longer crank. Moving forward also opens the hip angle which normally closes with a longer crank.
P.S. The only way to get a higher seat without increasing distance to the BB is to move it forward also. (higher seat increases distance to the pedals, but forward seat decreases distance to the pedals...so they cancel out but you get a higher "knee saving" seat in process). Of course after you do this you may or may not have to make a slight stem/handlebar change depending on how much pressure is on your hands