In one embodiment, an in-line tandem axle assembly comprising: a tandem wheel arm (46); a pair of wheel connecting assemblies (44A, 44B), each comprising a hub (60A, 60B) and a spindle (58A, 58B); a pair of mounts (50A, 50B) coupled respectively to the pair of wheel connecting assemblies; a pair of wheels (52A, 52B) coupled respectively to the pair of wheel connecting assemblies, the pair of wheels separated by the tandem wheel arm and in a same fore-and-aft position; and plural pairs of parallel links (48A, 48B) of equal length pivotably mounted to the pair of mounts and pivotably mounted to the tandem wheel arm.