A dropper post assembly for supporting a bicycle seat may include an outer tube extending along a post axis and an inner tube configured to be axially slidable within the outer tube by a travel distance that is at least 200 mm between a retracted and an extended position. The inner tube may have an outer diameter that is between 25.5 mm and 30 mm, and when the inner tube is in the extended position a moment of inertia (Ix) taken adjacent the seat collar is at least 11,000 mm4. A spring cartridge may have an unlocked configuration in which the spring cartridge exerts an extension force (FE) on the inner tube that biases the inner tube toward the extended position, and a locked configuration in which the spring cartridge is operable to generate a degassing force (FD) of between about 90 lbs and about 140 lbs to resist movement of the inner tube toward the retracted configuration. An actuator may be operable to change the spring cartridge between the locked configuration and the unlocked configuration.