What Makes an Alloy Wheel Brush Different than Other Wheel Brushes?
An alloy wheel brush is very soft. Alloy wheels can scratch very easily, so using a brush that is specially designed to work with alloy wheels is a good idea. A nylon bristle brush is too stiff and hard for alloy wheels, and a wire brush is out of the question. Using the correct type of brush on your wheels is important, because rims tend to be expensive and scratching them with a brush can be depressing to say the least. Alloy wheel brushes are available from most auto parts stores as well as online. Prices range from $5 to $20.
For more info, see What to Look for in a Wheel Cleaning Brush