Iron removers are great for wheels. They really dissolve brake deposits well. I did my new car with DoDo Juice Ferrous Dueller and got nothing off the paintwork and glass. I also did my better half's 6 year old car and got only very little effect on the paint and glass. But the wheels bled purple iron deposits and came up the best I've ever managed.
As above, the paint cleansing effect is of greater use for a car parked near railways or any other source if iron dust.
For my rural setting it's really just a wheel thing.