There is disclosed a motorcycle sidecar which has a single wheel (12) on a king post (13), a load supporting tray (11) which may optionally form a mudguard for the wheel, and a framework. The framework supports at least each end of the tray (11) and consists of two vertically disposed parallelogram linkages between the motorcycle and the wheel (12). The top member of the front parallelogram linkage is connected to the top member of the rear one to form a U-shaped upper link (15). The lowest members are connected similarly to form a U-shaped lower link (16). The king post (13) is attached pivotally to the connecting members of the links (15,16). When the motorcycle is leaned into a corner, the king post (13) leans at a similar angle while the wheel (12) remains on the ground and the tray (11) remains substantially horizontal.