because brake cleaner has some strong solvents in it, I would try useing a power washer first, you might even take them to a car wash and use the soapy scrub brush on the "tire" setting, then high presure hot soapy water should take most of it off, what's left should be able to be removed with a scouring pad and some brake cleaner.
I have the same issue with the "baked-on" brake dust on my VX wheels. For mine the damage has gone through the clearcoat and paint, so there is nothing that will bring them back to their OEM beauty without some stripping of the wheels and some new paint.
I might do a how-to on this very topic since I'll be picking up a set of painted black VX wheels tomorrow for winter tires. (For a great deal of $125 with good tires! YAYA)
On the never-ending quest for better gas mileage...
Guys, please try some brillo pads. This stuff works wonders and will get all of that black crud out of there. I went to the dollar store and bought a the cheap brillo pads, not the name brand BRILLO ones. When I picked up my VX, the wheels had all of the black dust on them and one wheel was almost completely black on the inside. I started off using a sponge with the green hard side. That worked a little but didn't get all of it. I tried the pad and the wheels look new. No damage Try it
After trying an "all wheels" cleaner with limited success, I bought an etching wheel cleaner for non-clearcoated wheels. Along with a stiff bristle brush, it worked great, removed all unsightly brake dust residue and didn't damage the clearcoat. YMMV