I always find it difficult to clean the inside of the rims, even when using a good wheel cleaner. I used Griot's HD Wheel Cleaner on the truck last week. Worked great but the rims still have areas of dirt. I used one of those elongated wheel brushes to get in between, but it didn't come out 100%. Ideally I'd like to take the wheels off to clean. I may have to go underneath and just hit them from the inside.