Brake dust baking embedding itself onto wheels has always been a problem for BMW's. To this day, BMW's, by far, have the most obvious wheel and brake dust problems.
I will give you a few ways to possibly solve this. All ways have been tested by myself, and worked. If one does not, simply try the next. Before doing any of these, make sure to try them in a small inconspicuous spot before applying to the entire wheel.
1. Purchase McGuires "All Purpose Cleaner". It comes in a blue jug. It is meant to be diluted, although it's more of a time factor. The longer you let it sit on the wheel before rinsing, the greater it will eat through any protective/clear coating you have on your wheels. At the same time, the length of time you leave your APC on the wheel might be the determining factor of it working or not.
If McGuires APC does not work, try p21s products. They are somewhat of a detailer's secret, although you might be interested. You can purchase these products here:
http://www.classicgarage.com/p2wheelclean.html
If I was there in person to feel the surface of these stains/pits, I would be able to give you an instant and definite answer. But I am not, so my last suggestion would be to simply buy a clay bar. Clay bars are typically used on paint, but due to their adhesivness, it might work for your problem.
Whatever you do, don't ever touch your car, paint, or wheels with anything that might scratch. Including Terry cloth towels. It's the most common mistake in detailing. To prevent this problem in the future, it is imperative you regularly clean your wheels. Buy a soft wheel brush and some wheel cleaner. Simply spray the NON-ACIDIC wheel cleaner on your wheels and brush aggressively with wheel brush.
Click here:
http://www.superiorcarcare.net/zymbritspray.html
Once you have applied this, enter the car wash to ensure a proper rinse or spray with hose. Make sure you get as much of it off before allowing wheels to dry.
If the instructions above do not work, it is due to pitting. Hopefully your wheels have not pitted beyond a fixable stage at this point. If it has, they cannot be fixed unless you reapply a new coat or finish.
Don't stress, everyone needs to learn sometime.
If you want to know more, then please feel free to email me.
dan@esportsmagazine.com