If you look at my photos from the Wheel Well modification in the link below, the wheel is not centered in the wheel well and the wheel is also very close to the frame.
http://home.comcast.net/~trailmanor/whlwell.htm
My guess it is just a normal part of the manufacturing process.
I've had no abnormal tire wear. I changed out the tires in 2005 when they were six years old and those tires had no abnormal wear.