They have some positive camber built into the axle. In other words, the distance between the tops of the tires is greater than at the bottom. It's done to make it easier to steer, easier to operate. It causes no abnormal wear on the tires when it's used for normal tractor purposes, like in the dirt, gravel, etc. Used on pavement, it won't matter if it was zero camber and zero toe, it's going to wear the tires, period. They're not designed for pavement or hard pack-which is why they say NHS on them (non-highway-service). The only adjustment that most tractors have is toe, and if you look at the specifications, it's a wide range, like 0 inch to 1.5 inch toe-in. This tells me that it's not critical as long as it's close. Final thought for now is look at your tie rods. It's not uncommon to bend them, and this will cause excessive toe.
