A bicycle crank assembly is provided with a crank arm including a front side surface and a back side surface. The crank arm has a crank axle mounting portion with a crank axle receiving opening defined by an axle coupling structure. The axle coupling structure at least includes a plurality of full length splines and at least one short spline. The full length splines extends completely in an axial direction of the crank axle receiving opening from a first axial end edge to a second axial end edge. The short spline extends in the axial direction with a truncated end positioned adjacent one of the first and second axial end edges such that the at least one short spline does not extend completely from the other of the first and second axial end edges to the one of the first and second axial end edges.