Have you tried Meguiars Hot Wheels (I think that's the name, it comes in a pink bottle). Works really good. I detailed a Jeep Cherokee last year with rims that were suppose to be chrome, the Meguiars removed the major brake dust build up with just a couple of applications and a rag. Wheels were shinier than new

1999 Contour SVT #1966/2760, Silver Frost/Midnight Blue Koni Kit, Mille Miglia MM-S rims, B&M shifter, Stazi mesh, SFCs, optimized Y-pipe & TB, SS break lines, K&N drop-in, Infinity Kappa speakers, MTX amp/sub