[Fr. Frank]

This can also be cause by trailering over potholes.

I drove a perfectly good trailer to Massachusetts in October to pick up my Seafari, and came back with exactly the same problem, cause by the extremely rough roads in the North East. Had it checked, and the verdict was that I needed a new axle, as straightening the stubs and spindles costs more than a new axle.

If your problem is just toe, it's an impact forward of the caster point. If you also have camber issues, weight may also be a problem. (As your axle is a torsion axle, you also have to account a little bit for caster position, which affects trail angle)