Joel,
look at the 3/4 Ton Rims thread under this same forum. The trailer reference is listed there.
From reading what I could find on the net, I think that the trailer wheels are not made to the same high speed balance specs. They are definitely as heavy or heavier than a corresponding truck rims. It is their duty to say that they are rated for trailer use only. I believe that the white spoked jobs are trailer wheels also.
