A bicycle seat post assembly includes a seat post that has a barrel, a cradle assembly, and a tilt mechanism. The cradle assembly is received in the barrel to secure a saddle to the seat post. The tilt mechanism is received in the barrel for setting saddle tilt. The tilt mechanism has at least one expander configured to at least expand. The expander is positioned in the barrel to exert a torque on the cradle assembly during expansion that causes the cradle assembly to rotate.