Height adjustable seat posts for bicycles are described herein. An example height adjustable seat post includes an upper tube and a lower tube configured in a telescopic arrangement. The height adjustable seat post also includes a shaft coupled to the lower tube and extending into the upper tube a piston assembly coupled to the shaft and disposed in the upper tube. The piston assembly includes a piston dividing the upper tube into a first chamber and a second chamber. The first and second chambers are filled with fluid. The piston assembly includes a valve operable between a closed state in which the fluid is blocked from flowing between the first and second chambers and an open state to enable the fluid to flow between the first and second chambers. The height adjustable seat post also includes a solenoid to control the valve.