0frollardBest Answer 9 years ago ReplyUpvoteThere are 3 types of cranks on bicycles (that I can think of) One piece units are one solid bar with 2 bends - usually on cheaper/kids bikes - not easy to transplant because the bar has to thread through the bike frame. Cranks that bolt on with an axial nut - a 3/4ish nut that threads directly onto the crank axle. The nuts are goofy - if I recall one is right threaded and the other is left threaded. This is so that it doesn't unscrew with the constant 'forward' rotation of the axle. i.e. on the left side it is a left-handed thread, on the right side it's a right handed thread. Sometimes they are both left handed threads. Cranks that have a nut and bolt that tighten the crank's grip on the crank axle - loosen those and take the crank off.