Many bike shops that sell cruisers (HD) sell a cleaner called S100 and swear by it I tried this on my dirty wheels and rear suspension. The direction call for spraying it, let it sit for just a few minutes and rinse with high-pressure water.
I once asked a detailer how they got my car's wheels so clean when they had caked on brake dust, and discovered Meguir's Detailer Wheel Brightener. Iv're been pleased using this on the bike before for wheels, side/centerstand, and rear suspension. This WILL take of brake dust, grease, and dirt with no scrubbing (nice with those Burgman spokes!). It might take a second application, but no more even for really bake on brake dust. Spray on, wait 5 minutes and spray off with a high-pressure hose. Things are left nice and clean and shiny.
Maybe HD owner have a better technique, but I could get the same result with the S100. Maybe I lacked the experience of Harley folks, but the Meguiar's results seemed much more idiot proof. I'm going to give my bottle of S100 to my son for his Harley.
It may take some searching to find Meguir's Detailer Wheel Brightener as it's a product for professional detailers and car washes; but it's really worth finding.