These are chrome plated aluminum wheels, right?
Rust comes from the oxidation of something ferrous, not from aluminum, nickel, or chromium.
So I'd think that the rust spots are from ferrous contamination that's stuck to/embedded in the wheels.
So I'd approach it like rust-blooms on paint- clay and/or some kind of acid.
Bostonsfavson said:
So it's chrome/nickel/aluminum? Why no black residue then?
The black residue comes from oxidation/tarnish being cleaned off certain soft metals (like aluminum or silver).
So in this case, a black residue would tell you it's bare aluminum, that black stuff is the oxidized aluminum being polished off (or, for another example, the oxidized/tarnished silver when you polish that).
Chrome's so hard that polishes generally just take off contamination that's on top of the chrome; it's not like you see "polished off chromium" on your buffing medium. My polishing cloths don't turn black when I polish chrome, they just get dirty.