## How much air would it take to float a car in water?

I just watched Transporter 3… There is a scene where he sank his car in a lake. He vents the air from his tires into a bag which balloons his car back to the surface. My question is, how much air would this actually take, and how much air is actually in a set of tires?

I’ve been guessing about 3000 lbs for the car, and we can assume his tires are filled to about 45 psi or roughly 3 bar just to give him the benefit of the doubt. I need to know the internal volume of a typical tire, and also the displacement of a car once water has filled the cab and the air spaces in the trunk and engine. The measurements of a baled car would do nicely.

Although air compresses at depth, let’s also assume he inflates everything near enough to the surface to get the full volume of air at 1 bar (14 psi).

Thanks for the insight!

Thanks for the comments so far!

I figured that at 3000 lbs we need to get to a total displacement of 1360 liters between the car and the air, and he just won’t have enough. I’m really trying to find out if he has more like 1/2 enough air, or 1/10th, or what?

I found some very diverse answers for the volume of air in a tire and no info on the displacement of a submerged car, so I’m really looking for good values for those parameters which will allow me to work the problem.

I estimate that he was at about 10 m or 30 feet depth so likely the air wouldn’t expand when let out of the tires, but I’m really trying for a best case scenario to test plausibility. So again, let’s assume he’s actually very close to the surface

Thanks again!