Please don't take my word for it, think about this - given your car example, that formula gives you a speed at which the car will hydroplane if you drive over a big enough puddle, if you put the anchors on, and give the wheels resistance to rotation, you can get the car to hydroplane at a much lower speed, particularly when your talking reverted rubber hydroplaning (when the surface of the tyre melts to form a liquid film) - this is essentialy a skid.