I have bought many types of metal wheels. I use Bachmann which are the same as Aristo but cheaper from the wholesaler I use. All my wheelsets have been out of gauge and needed to be corrected. Try taking your plastic wheels off any Aristo, USA, Bachmann or LGB car and you will find the same thing. Many people blame derailments on poor track, when in many cases they have never checked the gauge of their wheelsets. This is something I always do when I get a new car out of the box, and when I go to change my wheels to metal.
Bob