I used one of the stronger wheel cleaners and Mr. clean eraser on the INSIDE of my wheels to clean off 15 years of brake dust. I would spray on cleaner, set for 1-2 minutes, scrub, rinse and repeat untill clean.
Do not let these cleaners set on the front surface too long as it might damage the front finish as many of these cleaners use acid to help clean.
No problems now that I have ceramic low dust pads.