As many of you know, Jalopnik employs some very sophisticated user-monitoring software, so we know all about you. Which is why I feel confident in saying that, based on your demographic data, most Jalopnik readers will likely drive their cars deliberately into a lake, pool or other body of water at some point. And, as always, I'm here to help.
I said "deliberately" up there because I want to make an important distinction: this piece is about how to, after you plunge your car into the water, stay underwater for a bit. There's tons of reasons why you'd want to do this, most involving you being on the run from someone– bad guys, cops (if you're the bad guy), bears, bear cops (if you're the bad bear), etc. If you're just driving into a body of water by accident, just get the hell to the surface, and don't even worry about breathing out of the tires. Okay?
This scenario is most famously known from the James Bond movie A View To A Kill, where Bond has to make bad folks (or were they bears?) think he's dead after the Rolls he was in plunges into a lake. He lingers underwater by breathing air from the tires. The way he does it always struck me as odd, though— he somehow manages to open the valve stem with his mouth and breathe the air. Tire valve stems just don't work like that.
Mythbusters tried this out as well, and decided the myth was busted— they couldn't find a good way to get air into a mouth without excess water. They tried the valve stem, which didn't work, and they tried cutting a hole in the sidewall with a knife, which didn't work. But I think they, unusually, gave up too soon— I think this can be done.
Let's start from the beginning. You're in your car, the bad guys/bears are barreling up behind you, and you're running out of road and options. You see a lake and decide that's your out. Now what?
First, since you want to actually get out of the car when it hits the water, roll down your window. Unless you're in a well-maintained vintage Beetle, that car's gonna fill with water and sink, but while it's sinking, if your window is up, the pressure differences between the inside of the car and outside will be such that you can't open the door until the car is totally filled. You don't want that. Opening the window lets you exit much quicker, without having to force the door open. If you have roll-down windows, you could do this after you hit water, but electric windows (and the car's whole electrical system) will be compromised and shorting out when all that conductive water floods in, so best get the window down first.
Next, if you can tell, try and go for an area not too deep. If you're too far down, the pressures will be high enough that the air in the tire can't escape, and it's that much further to the surface. So, you know, see what you can do. While you're doing that, if at all possible, get a knife of some kind. Or at least something sharp you can take with you out of the car. A little pocketknife would be ideal; if you don't have anything, I think we can manage, but a knife will make it much easier.
Okay, you've sucked in a big last easy breath, plunged into the water, enjoyed the shock and thrill, clenched your buttocks so very tightly, and squirmed out the window. Outside the car, be careful– most cars are front-engined and will plummet nose-first pretty quickly; it may flip upside-down as well, which will actually be a bit easier for you, as you'll have better access to the tires. Hopefully the car has settled on the bottom now, and you can get to one of the tires.
Once at the tire, find the valve stem– that little nozzle thing you use to fill the tires with air. It has a little valve in the end, actuated by a tiny pin, and unless you had a tongue transplant from a hummingbird or something, it's too small to push with tongue or fingers. The stem itself has a brass sleeve extending down about an inch in the tube, so we can't cut through that; our best bet it to focus on where the stem meets the rim. It should slightly bulge out, forming a little bulb at the base of the stem.
This little rubber bulb is just rubber, no brass. You can feel where the inner metal sleeve ends in the stem by bending it back and forth. Now, bend the stem so you can feel where the inner sleeve ends, close to the base. With your knife, cut the stem off as close to the metal inner sleeve as you can— the goal is to leave as much rubber on the tire as possible. If you have no knife, you can twist and bend and try and chew your way through. This won't be easy, but with all that adrenaline in your system, it should be possible. Use those canines!
If all went well, you should have removed the valve stem and left on the tire is a bubbling hole (plug with your finger for now) surrounded by a small rubber mound/ring. Now here's what you have to do: get in there and make a tight seal on the hole with your lips, and use your tongue to plug the hole. You're really going to need to get your face right in there, and, depending on the rims, wheels, and hubcaps, this may be hard or easy.
That's the basic idea: get the metal part of the valve stem off, and use the remaining rubber rim and hole to get the air out of the tire. As far as how much air you can get out of the tires, and how long you can hide under water, that'll take some math. The volume of air in a tire can be figured out by figuring out the volume of the tire. We can use the formula for a torus, which is (1/4) * pi2 * (r1 + r2) * (r1 - r2)2, then double that since tires hold around twice the pressure of regular air. But screw that, you're about to drown, you don't want to do math. An average-sized tire has about 10 liters of air, and an average full lungful for an adult male is about 6 liters. But you don't need to fill those lungs to capacity, actual breaths are much less. So, let's say half that, 3 liters, which would give you a bit over three good breaths per tire. Let's say you can last, oh, a minute and a half per breath, so each tire gets you, roughly five minutes. That by four is 20 minutes! That should be plenty of time to wait out anyone on the surface.
I tried this out on a wheel from my wife's old 1978 Buick Skylark, steel wheel, no hubcap, and, while it tasted terrible and felt creepily, uh, intimate, it did work. I could suck air from the hole, and control the airflow with my tongue.
I didn't try this underwater, though. Gawker doesn't pay quite that much. So, you know, no guarantees.