[Earthling789]

Dawn dish soap is one of the best degreasers (and cheapest) out there. Squirt some directly on the tire, scrub a bit with wet brush or wet sponge to get a lather going... then hose off until everything is removed, clean, and clear.

I use the same thing to clean grease off other things... mower, grill, bike, etc.... It works great!

You can dilute it for "less greasy" jobs... a teaspoon or two in a half-gallon of water... and scrub away!