rideheight must be the mm you drop the car,,cant think of anything else...but yeah he got a point, say if you drop it 40mm on standard wheels and they change then to 18" the car might sit higher than before.
40mm is nothing,,think mine is dropped like 70mm or something B) The IS200 is Suv-ish in standard form
i would say a 50mm drop is Ok for most roads.