Ok! mine were filthy with brake dust and generaly very much in need of a clean , id washed them in the normal way basicaly wetting them and giving them a little wipe, and obviously before long they were in a mess, possibly like yours, which is probably what prompted this post right?

I had taken the dog out for a walk a few weeks back and the bugger pissed on my wheel , so I grabbed a bucket of water and flung it over the wheel concerned and believe it or not the baked in brake dust came off with out any bother.

So am currently training the dog to piss on the wheel of the car , problem is he seems to be preffering the rear wheels which dont get nearly as bad. Now I aint gonna go to the extent of following him about the garden with a basin or bucket , but I cant even start to explain how well it worked and how surprised I was.

A little unusual I know, hard to believe granted! whether am talking piss or not.....you decide!

BTW he is a Golden retriever and he is fed mainly on dry dog food.

Or you could try wonder wheels