A wheeled carrier device such as a baby stroller, golf cart, child carrier, or general carrier or cargo cart, comprising a bottom frame with at least two rear wheels and at least one front wheel, and may include a movably mounted upper carrier frame with a selectively removable, adjustable and/or reversible carrying element which may include child seating, with a unique wheel folding mechanism that interconnects all the wheels, so that simple movement of a wheel folding grasp synchronously moves all the wheels between the operative, rolling position and their stowed fold flat positions parallel with the bottom frame, with the wheel folding mechanism operable independently of collapsing movement of an optional upper carrier frame which also folds flat and parallel with the bottom frame.