a 19 inch wheel will still slow you down, even if it is the same weight as the comparable 17'' wheel. it's not only the weight of the larger wheel's that slows you down, its also the rotational intertia.
basically its this. even though they might weigh the same, the weight is farther away from the axle in a 19'' wheel. which means that it takes more effort for the car to turn the wheel. for an idea of how this works, go up to a large door and push it closed from the middle of the door. then open it back up and try again from the very edge of the door. and once again from right next to the pivot point of the door.
if i screwed up in my explanation, someone please correct me