Tires are not just mounted completely straight front to back, nor are they perpendicular to the pavement. The attached picture illustrates the basic elements of camber, castor, toe-in, and toe-out. Even though our trailers have solid axles, manufacturers can still configure these alignment settings when the axles are made and when they are mounted. Thus, when "flipping" axles, making careful measurements prior to welding on the new spring perches is essential. Dexter sells an "axle flipping kit" that helps you align the new perches with the old perches. If done carefully, the axles can be relocated without changing the factory camber, castor, etc.

Hope this is useful-
Steve