Full transcript of “Neil deGrasse Tyson Explains Tire Pressure”. Click a timestamp to open the video at that moment. Need another video? Use the YouTube transcript generator.
0:00 foreign ER for you all right I just figured it's something that people think they know about but it really don't okay so I just thought I would sort of bring it up and it has to do with tire pressure tire pressure tire pressure tired okay all right all right all right okay are you ready I'm really not ready but this is um you know where Hey listen I feel like this at this point you know uh with them paddled out it's time to ride the wave that's the way I feel we're out there just let's do it bring it on here you bring tire pressure
0:47 I'm like it's you got to be Zen enough to go ahead and jump up it's time to get up and and surf this wave that's all all right let's do it so tire pressure first of all if you have a tire with quote no air in it of course there's air in it because there's the atmospheric air is in it right okay and atmosphere has its own pressure and this is the weight of a column of air from Earth's surface all the way up to the edge of the atmosphere if you had found a way to weigh this we I think we might have talked about this in another explainer but if you if you have like one square inch or one square anything but one square inch and have weigh that column of air it will weigh 14.7 pounds nice okay and the way air Works fluids
1:32 work is that pressure I would say yes it's sitting on the scale but that pressure manifests in every direction because the molecules are vibrating in every direction right so so right now I have 14.7 pounds per square inch on one side of my hand and on the other side above above and below and so everything's all equal now every direction so I don't even notice it like you're not getting crushed by your 14 pound air wreck it doesn't make a difference correct pushing down on you and pushing up and pushing up it's even Steven whereas if I have a suction cup right and I press out the air that would otherwise eyes be balancing it if I press it out yeah so now I say lift
2:18 up the suction cup because I can't it's sucking me down no it's not why can't you pick up like seven pounds per square inch per square putting it down pushing it it's really not sucking anything yes suction cups don't suck they don't suck wait they got a bad rap but still alive they don't suck they don't suck so if you had 10 square inches of area on this on the suction cup right I can ask you how much force would it take to pull the suction cup off the surface so I gotta go 10 square inches times 14.7 pounds per and then push back in that opposite direction and okay that gets you 147 pounds so if you can pull 147 pounds or more it pops right off or you
3:04 could cheat and pop open a little uh Pearl in the edge and and then let the nature do it for you air slips in and then it just comes on right then you let nature help you out okay so the point is if you fill a tire to what we call 10 pounds per square inch that's 10 pounds on top of the air pressure that's already in there right that's all I'm saying right all right so first of all just lay that out cool so now have you noticed or perhaps not that on bicycle tires the thinner the skinnier the tube yes the what the less air you should keep putting in it once it gets hard because it will pop
3:51 I'm telling you okay but from experience okay okay if you look at the ratings of thin tires in essentially every case depending what they're made of but in every case they have a higher pounds per square inch rating than the bigger tires okay hi okay I don't I didn't know that to be honest yes yes okay this is the first I'm ever hearing of this okay because you never got to pay attention well no I'm gonna tell you why because I come from the times when you will feel your tire and then you just push down on it and if you can actually push it and flatten it you're like now
4:36 put some more air in there okay oh that was how you measure it yeah and then once you couldn't do that you'd be like all right it's time to go this time yeah yeah you want to use a gauge okay right exactly right all right so and the cage is calibrated to not count air pressure all right so that's how they work all right so now watch you sitting on your bicycle and the bicycle has tires and the tires are in contact with the road obviously the heavier you heavier you are the flatter the tire is going to look true okay we that okay you know this well yeah why does the tire flatten if you're heavier why why does it do that I'm going to tell you why because at all times the pressure inside the tire
5:24 per square inch times the square inches of Tire in contact with the road has to equal your weight plus the weight of the bicycle at all times at all times okay Okay so okay so all right so if I have a big time like a kid's Tire okay if I have one of those kind of tires and it's huge it might take 30 pounds per square inch that's not uncommon okay 30 20 to 30 pounds per square inch and there's a square inch of it in contact in the back and a square inch in contact with the front add those up it
6:10 is holding up 60 pounds that could be the weight of the bicycle plus the weight of the kit okay you put a heavy hit on there the bicycle has to hold up more weight against the air pressure in the tires so the the tires flatten a little more adding more surface area right okay adding more area so that now you go go the air pressure times the the square inches in touch with the ground and now that'll equal the weight of the heavier kid okay so I I'm heavy all right I'm 260 pounds right now okay okay all right so now I ride a bicycle with very narrow tires the air pressure in those tires is 130
6:58 pounds per square inch 130 pounds okay per tire so Watch What Happens I I deflate it to that amount and those tires will flatten to slightly more than a square inch per tire because it's my weight plus the weight of the 22 pound bicycle it's got to hold up 280 pounds right so it's going to flatten slightly more than a square inch on each and that is my that is my tire okay okay so so farm tractors have huge tires right huge tires in that way they put relatively low air
7:43 pressure in them that way when the tires roll over the crops ah it does minimal damage right because you're not digging in you're not digging you don't need that that's out that's the pressure brilliant okay you can still hold up the tractor right if you if you get enough area coming down otherwise you'd be leaving deep tracks in the road and you can't have that not in yourself it's like dune buggies they all have big giant wide like balloon tires well that one is to increase traction on Sand yeah because they don't dig into the sand is what I'm saying they don't dig into the sand correct and so so tire pressure is all about how much weight are you holding up and they will tell you in your car if you're
8:29 gonna carry a heavy load increase the air pressure in your tires so that your tires don't flatten out right okay if you increase the pressure from let's say uh you know 35 pounds to 45 pounds per square inch that gets you extra support in all of your tires in a typical car you know how wide is it is a tire you know it might be a foot you know 20 18 inches is a typical tire no no not across yeah what are you doing riding the Indy 500 what 18 inches yeah okay all right I'll give it to you I don't know I mean we're both City people so I don't you know well yeah I mean I I drive an SUV though
9:17 okay you said car and I'm I'm really not thinking SUV okay yeah fine okay so a car might be and it's not electric and I'm very ashamed but I'm buying an electric car so I know you already have one eventually I'm late to the game so here's what you do you can do this experiment at home please go look at how much of your tire is touching the ground measure that okay front to back and then across the width so you'll get two measurements it might be like five inches uh front to back flattening on the ground and then measure the the width of the tire multiply those numbers by each other that's the square inches per tire multiply that by four and that's going to give you the weight of your car
10:02 get out of here yes that's pretty wild I mean that makes sense just from what you just said correct uh there's only one problem what's that I did not give a damn how much my car weighs [Laughter] where between you're an SUV somewhere between 1500 pounds and a ton 2 000 something like that that makes sense but all just by measuring the square inches so oh sorry you have to know what your tire pressure is first right okay it's in the side Pole or or maybe if you're a modern car it tells you yeah they can tell you on the dashboard on the dashboard and so you got four tires and get the area so it's front to back
10:49 in contact and then the width multiply those two numbers then multiply by four and multiply by your air pressure that's the way that's the weight of your car and so you it's a way to weigh your car without going to a scale that's pretty cool your tires are doing it all by themselves and now uh all I need to do is figure out the calculation to um put uh Aunt Gail and uncle Daryl in the back seat um that's a different calculation so it'll either flatten the tires some more believe me so then the car has given itself a way to hold them up or you increase the air pressure so that at the same area in contact with the ground it holds them up that's what okay that's sweet and generally they tell you to increase the air pressure because it's better for gas
11:35 mileage and things right yeah all right you got it dude that's cool but there's mass in everything it really is I gotta tell you I I was worried when you said tire pressure okay I really will I was worried man so just just a quick one a quick one doesn't belong in this explainer at all but while we're here do you know your hat size I don't you don't okay uh I know it's small though it's like seven it's a seven or six that wouldn't be small if it's seven it wouldn't be small okay so here's what you do measure get a tape measure and measure the circumference of your head in inches okay right where the brim would sit all right okay write down that number and then divide it by pi that's
12:21 your hat size okay I'm definitely going to do that okay I can't wait to get this over with because that's a damn that's the first thing I'm gonna do as soon as we get off this call there's measurements and everything yeah in inches where the brim will sit right and um divided by pi correct and that's your hat size it'll fit perfectly every time that's that's pretty cool there are two very good things I've learned right now that's probably your head size in America elsewhere I don't know how they do it well don't worry because I'm not buying a hat from any place but America okay damn right in the way ahead make sure my American hat is made in China that's right the way you pulling off my hat says me in China pull up my hat and it'll say make
13:07 America hat again make America hat again and boom I am right baby what the hell I'm that's what I'm talking about this is evidence it's time to end this explainer okay it's been he had another Star Talk explainer Chuck thanks for being there always a pleasure all right Neil deGrasse Tyson keep looking up foreign [Music]
