A bicycle crankshaft assembly in accordance with the present invention comprises a frame tube having first and second end portions and defining a passage extending between the end portions. The first end portion define a first opening, and the second end portion define a second opening different to the first opening. An axle is securely assembled into the passage from the second end portion and the axle includes a bushing with a crankshaft rotationally supported therein. The crankshaft includes first and second coupling portions extending over the first and second openings of the first and second end portions of the frame tube. Wherein the first opening is dimensioned such that a first end of the bushing is limited from extending therethrough.