Stephen ... it's normal to have some arch in the middle of the axle
... trailer axles do this so that when you put some load on the axle
, the axle
tends to straighten, keeping the tire in good contact with the ground.
Your axle looks fine.
Could be the picture, but your tire doesn't appear to be wearing all that abnormally. It appears that the thread depth on both the inner and outer edges is about the same ... with more thread in the middle, which means the tires
were probably run a bit underinflated.
A bad axle will cause one edge of the tire to wear off completely while the other edge looks brand new, with no wear at all.