I use Griot's Garage Heavy Duty Wheel Cleaner. It's PH Balanced,
Approved by BBS, the maker of rims for Ferrari, Porsche, etc. It will get the road tar, brake dust and dirt. Apply let dwell then use wheel woollies.
If you are looking to get some baked on road muck, you could use Stoners Tarminator first, but you should still go back over them with a wheel cleaner.
For the cheap steel wheels with plastic hub-caps, I'll use APC.