Simple Green will work wonders on grease. Might want to do this at a carwash [do-it-yourself place], but a high pressure nozzle on your hose will work too.

Soak the entire wheel in SG, just layer the wheel. Let it sit for a few minutes. Take a sponge with some texture [but make sure it won't scratch the finish] and use a lot of elbow grease. Use more SG wheen needed. Take a clean trash can or heavy duty plastic storage container [very cheap at local dollar stores] and fill it with lots of water. Soak the wheel in the water. Then hose the wheel off [preferably a pressurised hose like the do-it-yourself car washes have]. Let dry.