If everything is lined up correctly - clean your rims and your brake pads with Simple Green (if you can find some) or Formula 409 if you can't. Last resort is Windex, but that is not as good as a grease cutter like 409 and nothing beats Simple Green for cleaning your brakes.
Also, spray some Tri-Flow oil into your brake cables at all junction points to make your brakes slide smoother.
Finally - if you want brakes that work. Throw out your crappy black rims and get some chrome plated rims and never worry about brakes again.
