That's to fit the steering joints, bushings and bearings, as well as the suspension and brake systems, while keeping the axle as wide as possible for maximum stability.

Semi-trucks are a pretty common sight on today's roads, and they're all about maximum capability. It's one of the reasons why ...

Looking at the Wave pedal in profile, the front half of the pedal has a concave shape, while the rear of the pedal is sloped back from the axle in a more convex shape.