So you use shorter cranks - then you have to spin faster to get the same power, right? The power to rpm curve is different for different folks. For some people, continuous power decreases at high rpm because of the oxygen costs of spinning fast. Get on your trainer and spin at 120 for 30'. See what your average power or speed was. When one runs out of gears on steep climbs and rpm drops, then leg force has to increase with shorter cranks to get the same power. That sucks. Thus it depends on the rider, their training and physiology, and on the course. I'm 5'6", short legs, ride 170 and 175 cranks. I wouldn't go shorter. It's like, "why would I do that?"
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