Guys, if you have baked on brake dust I've found that non of the commercially available cleaners work well. I recommend Poor Boy's World brake dust cleaner. It really works wonders. Just spray it on, and hose it off. I let it sit for a few minutes, and I did use a brush, but when I sprayed it off with water, it all melted away.

http://www.poorboysworld.com/spray-rinse.htm