My wife has a 2004 Grand Caravan with 16" wheels. I want to put wider profile tires on her existing wheels. Can this be done without significantly lowering the total diameter of her tires and messing up the speedometer readings?

I had a friend who would ocassionally put 16" 50 series tires on 15" wheels in place of his 60 series tires to accomplish the same thing 20 years ago. Is this still feasible?