Originally Posted by
chasm54
The "pedalling efficiency thing" is a myth, imo. Longer cranks give greater leverage, yes, so you can probably push a bigger gear. But they slow your cadence, so you may not accelerate as well, there's a bigger "dead spot" at the top of the stroke (which is inefficient) and they'll be harder on your knees. If anything I'd say we should be investigating the benefits of shorter cranks for shorter cyclists rather than longer ones for us tall guys, because there are likely to be efficiency advantages in reducing the acuteness of the angle through which the knee has to bend at the top of the stroke.
FWIW, I got a great deal on a used bike 15 years or so ago, exactly what I wanted except the previous owner had built it up with 170 cranks. He was 6'2"; I'm 6'4" and had always ridden 175s. I rode it a fair amount (it wasn't my only bike) for four or five years untilI destroyed it in a crash. I could spin like crazy on it, but it always felt a little cramped. I'm a lousy climber anyway, but I really couldn't go uphill on that bike. If I ever do another build (I have way more bikes than I need already), I'm going to try 180s.