An automatic swimming pool cleaner includes a body (18) and a wheeled undercarriage (42) for the body. The undercarriage comprises a first submerged surface (14) engaging section (50) and a normally leading second section (52). The second section is pivotable in elevation (α) relative to the first section. The pivotable second section enables the cleaner to negotiate sharp corners between a floor (14) and a wall (16) of the pool and further lengths a wheelbase provided by the first section during reverse motion of the cleaner. A surface engaging brake (81) on the second section facilitates change of direction during reverse motion of the cleaner.