Hi Andrew - your first post said hubs not road wheels so I took that to mean the rear hubs holding the sprockets. The amount of immersion time that the wheels would be in the petrol would not effect the rubber. I re-rubber the road wheels and have to use a flame torch to remove the old rubber. The rubber is also adhered to a substance called ebonite that forms the bond between the rubber and the metal of the rims. This is all explained in my thread on wheel re-rubbering. If you are still worried about the petrol/rubber thing, sit the wheels on top of a smaller container holding petrol, or as Lynn suggests, kerosine, and still use a stiff brush to wash the grease away with your choice of the two solvents.
Hey Lynn - I agree kero is a good solvent but kero to petrol is like diet beer to real beer or decafe coffee to real coffee. Live a little dangerously.
Bob