This morning, the DC area suffered a brief but very intense storm causing flash flooding. On radio station WTOP, AAA Mid-Atlantic spokesman Lon Anderson warned against driving through water. He said, in part, “Cars float easily due to the inflated tires.” :dubious:
Four tires inflated at 35 PSI are not going to significantly increase the bouyancy of a two-ton automobile. Cars float because they leak slowly, at least until the water level is pretty high. If inflated tires were the explanation then you could drive a car across the Potomac.
I’m not an automotive engineer so feel free to tell me I’m, er, all wet.
I’d think the risk is not that the car will float, but that floodwaters may be flowing deceptively fast, creating the risk that the vehicle will be swept off the road into deeper water.
As my sister found out some years ago, Jeeps cannot be used as flotation devices either.
Fortunately, not many people found out about that little mistake. Only the entire population of Philadelphia, after a picture of her in a canoe being rescued by the police prominently appeared in the Inquirer.
Or helium balloons. A friend of a friend of a friend was trying to transport a ton of filled helium ballons to a kids party in the back of his SUV. When he was bringing the last bunch of ballons to be loaded into the SUV he noticed the SUV was gone.
He thought it had been stolen until someone pointed up in the sky.
(P.S. for better gas mileage fill your tires with helium. It make the car lighter.)
This reminds me of the roofer who was interviewed in Jacksonville during a heat wave. Apparently working on roofs is really hot because they’re closer to the sun than those of us on the ground. Yeah, they’re 93 million miles, minus 25 feet… :rolleyes:
They do, however, explode after driving off a cliff, sometimes before they actually contact the ground. I know this by watching a series of documentaries about elite field agent of the British Secret Intelligence Service.
Hydroplaning has nothing to do with the buoyancy due to air in the tires. Hydroplaning occurs because of hydrostatic shock of the tire surface on the water; in other words, the tire hits a patch of water with sufficient force per unit area (pressure) that the water, which is essentially incompressible and has to move either into the treads or to the side in order for the tire to touch the road, can’t move out of the way, and thus the tire cannot attain traction. This isn’t too much of a problem as long as you are going straight forward, as the momentum of the vehicle will allow you to go into a straight line until you slow down enough that the tire makes contact, but becomes a severe problem if you try to go sideways (or the road makes a turn) as water has virtually no shear resistance and thus you continue forward, often with just enough traction to allow the vehicle to spin around its barycenter while continuing in a straight line, completely out of the driver’s control. The tires would behave this way if filled with air, marshmallow creme, Dapper Dan pomade, or ball bearings; the buoyancy of the tire has nothing to do with it.
