US Patent 10150533 Bicycle crank assembly

A bicycle crank assembly comprises a sprocket unit and a crank axle. The sprocket unit includes a sprocket having a rotational center axis. The sprocket includes a plurality of driving teeth. A total number of the plurality of driving teeth is equal to or larger than 38. The crank axle extends along the rotational center axis. The sprocket unit is movable relative to the crank axle in an axial direction of the rotational center axis within a movable range having an axial length equal to or smaller than 8 mm.