Well I had very simular stain's on my Echo that I just picked up. What I did was take the wheels off of the car that way it was easier to work with
Is the wheel painted in the section where you have your spots or is it polished??? Does it feel like overspray (from a spray can or something)?
1. Clean them with some dish soap and warm water with a soft scrub brush getting into the groves and such.
2. Mother's FX wheel cleaner with a sponge and scrub away.
3. If its still there some cleaner wax would do the trick if its painted.... if its polished brake out the wheel polish
4. After its all clean and such wax your wheels!!
If you have a Mr. Clean Magic eraser that might work also