In an amphibious ATV, the wheel bearings are housed in a spherical mounting-structure, because of possible angular misalignment. The spherical mounting-structure comprises separable primary and secondary elements. The new system provides that both elements are axially wide, being e.g as wide as the outer-race of the bearing. Now, the elements are highly resistant to every distortion, which means the mounting-structure can seal the bearings very effectively—both as to keeping dirt and water out, and keeping lubricant in.