| There are several wheel cleaners specifically for this purpose (removing brake dust from chrome wheels). Usually, they are in a spray bottle, you spray them on and hose them off. If there is heavy grime, you may need a second application or a small brush to work the cleaner into the crevasses.
Make sure to get one for chrome, there are several for aluminum rims, etc.You don't want one that will stain the chrome. I have seen these at Auto parts stores here (Auto Zone, Pep Boys, Kragen, et al.) | 
