Why is it that the front-wheel hubcaps on large vehicles are convex but the others are concave?

Question

On large vehicles (Trucks, buses, etc) the hub-caps on the front wheels are concave (stick out) whereas all the other wheels' hub-caps are concave (stick inwards), but on small vehicles (cars, 4WD's, etc) both sets of hub caps are the same.

Why is this???

Answer 1

well on trucks and buses it is like that cause there is duel tires on the rear and not the front if you turn the tire around it allows you to mount duel tires on the rear