There is described a wheel axle for an agricultural vehicle such as a combine harvester. The wheel axle has at least one wheel suspension (32a) arranged to maintain a wheel axle parallel to the supporting surface, through use of a linkage arrangement (36, 38, 40) which is pivotally coupled to the axle frame (30). The configuration of the wheel suspension allows for the wheel axis to passively follow the surface profile, as any loads transmitted through the wheel carrier act to level out the wheel suspension to align with the underlying surface. As the wheel axle is adjusted to lie parallel with the underlying surface, accordingly the ground-contacting surface area of the associated wheels is maximised.