Hi, I have an 04 roadster and the wheels are looking a bit tired, whiteish deposits on the castings. What,s the best way to get them restored?

 

Sounds like the Aluminum oxidation has slipped past the factory powder coating.
From most extreme to most easy:
Sandpaper, masking tape and primer/paint, or media blasting then powder coating, would take care of it. Quick and dirty might involve some patience, steel wool or fine sandpaper, and touch-up paint. Fingernail polish makes for a convenient touch-up, having a brush in the cap, depending on the extent of the oxidation. Worse case, your touch-up looks like poo, and you're no worse off than when you started. WD-40, Lemon Pledge, or a quick-detail product, might make small spots livable (keep it off your brake disc).
I'm only guessing. I'm not a detailing professional.
Let us know how it goes.

 

I was thinking our wheels are magnesium alloy? There are mag wheel cleaners, some of them pretty good.

 

Magnesium alloy? I've always assumed the "mag" wheels are Aluminum. I don't know that for a fact, but I was 99% sure. I reckon I'm asking for verification/clarification. If I'm not careful, I might learn something.

 

After looking it up on the internet I've learned the term "mag wheel" originally meant magnesium alloy wheel, later it became a synonym for all alloy wheels, including aluminium.

 

Thanks for the input, these wheels arn't painted look like raw casting , goner try some mag cleaner failing that I will paint the inner area's.

 

I've had a genuine mag alloy wheel and they do not like atmospheric corrosion! The metal simple seems to evaporate. I've never understood why alloy wheels should be called 'mags'....

 

That's wht I did with the rims on my 96.