Some products remove clear laquer that may be on the wheels. Your supposed to only use water and soap on wheels which have been refurbed. Obviously not the case for the standard DC5 wheels.
Well I use 2 Large Art brushes to brush it and and work at the hard stuff and then hose it off once the the dirt is lifted. If you leave it on too long then yeah it might eat away but then it clears the crap so well so easily I can live with being a bit careful with it :!: