Neil deGrasse Tyson Explains Tire Pressure

How much does air weigh? On this explainer, Neil deGrasse Tyson and comedian Chuck Nice explore how tire pressure works and how tires make the world go ‘round.
Is there still air in an empty tire? Find out how much air you need to put into a tire to hold up Neil. Why do bikes have thin tires and tractors have big ones? Discover how there’s math in everything…
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Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up!
#StarTalk #neildegrassetyson
00:00 - Air pressure & Tire pressure
03:30 - Pounds per square inch
09:10 - How much your car weighs
11:55 - Hat Size

[@StarTalk]

What kind of tires do you ride on?

[@bagyra]

The bald one's

[@aprylvanryn5898]

That depends on who Uber sends

[@ron28688]

I use round tires

[@Bondokill]

Rubber ones?

[@ferociouzmonk]

The rim.

[@ChronicGamer420]

Startalk always feels like a father teaching his son about the universe

[@Bondokill]

Chuck is his son

[@Bob-of-Zoid]

If I had listened to mine, I could very well be a flat earther! Not all fathers are equal, and I got real lucky having taken after my mother in the brain department!

[@zachrowell6795]

Kratos: BOY

[@ChronicGamer420]

@@Bondokill son or sun?

[@HalfSkullSenior]

Right! The laugh & comedy helps set the mood so much more for keeping attention.

[@rexberttechnica6702]

Chuck was referencing wheel diameter, not tire width. A typical passenger vehicle tire is 195 - 245 mm cross-sectional. Also, the gross vehicle weight and tire inflation pressure is on a sticker in the driver's door jamb.

[@kooooons]

With trucks and SUVs you're easily entering 265 territory.

[@kellyrobinson1780]

Yeah, but this is more funner! (Still like your comment though.)

[@charlieauxilien3396]

Yeah and an SUV weighs way more than 1500 pounds lol more like 4000 lbs

[@fantasticsound2085]

@@kooooons Sure, but 10-11" wide is still a far cry from 18". As was previously mentioned, Chuck was almost certainly referring to the diameter, not the tread width. (Which is what Neil was referencing at that point.

[@tharrrrrrr]

@@fantasticsound2085 *wheel diameter

[@prestigerealtyinc.dbaprest8694]

When Chuck said "There's one problem, I do not give a d*mn how much my car weighs" I actually laughed out loud. Chuck deserves a PHD in the science comedy niche, other hosts can learn from him.

[@SirCheeto47]

The editing on this video was AWESOME! Having the imagery pop in to match the explanations was a really nice touch.

[@StarTalk]

Nice to hear this feedback! Thank you, Sir Cheeto 🖖

[@andypeiffer5]

My Uncle taught me about tire pressure. He asked me how much PSI I use in my car, and I said 35. He then asked how much I would guess he puts in his tractor's tire, I said it has to be like 200. .... he said, 8. "Surface area" It blew my mind.

[@StarTalk]

Surface area is everything!

[@TheSilverShadow17]

​@@StarTalkIt definitely is especially in comparison to the skinny low profile tires that lot of high end exotics use, but since they are low profile they're also more vulnerable to damage and wear compared to beefier higher profile tires because they can be ran at a lower pressure and last much longer too.

[@SoidSnake]

At 8:53, I see that Neil was talking about the tire width which is usually around 225-255mm while Chuck thought you meant the diameter of the wheel which is usually around 16-20 inches, 17-18 is very common. For some reason rim diameter is measured in inches while tire width is measured in mm

[@dustmaker1000]

Only Neil can make air pressure in bicycle tires interesting

[@keithrange4457]

Agreed, love learning on this channel. I'm 42 and still learning and love that too ❤

[@eubenhadd462]

It's minor, but the tires themselves also have support in their structure aside from air pressure, depending on the type of tire. That's how run-flat tires work.

[@WV_COAL]

The first number on a tire size is the metric width of the tire. The second number is the percentage height of the sidewall, and the last number is the wheel size in inches typically. ex. 225/70/R16

[@TG-cm5mb]

What kind of car were you thinking of when you mentioned this particular size? Just curious...

[@lordgarion514]

They literally used metric, percentages, and imperial all on one product.

[@Eren-da-Jaeger]

@@TG-cm5mb all sort of cars. But when you go for bigger suv or truck or semi wheels then there is different measurements which is in inches.

[@flashcloud666]

Yeah, I was looking for someone in the comments to mention tire sizing. When Chuck said 18s he is referring to the size of the wheel that goes inside the tire. The width of his tires is in no way 18 inches.

[@Milesco]

@@flashcloud666 Yep. And that's why Neil was like "Wha...????"

[@JasonWW2000]

To be clear, the pressure # molded in the tire sidewall is the max and is only used to mount the tire on the rim. The tire can not tell you what pressure to drive on because that tire fits many different vehicles. Because the driving tire pressure is determined by the weight of the vehicle, look on the vehicle door sticker. 32-37 psi is pretty normal for average vehicle.

[@Nightcrawler333]

Thanks for this info 👍👍

[@luisbressantmtbseries.5232]

The tire machines in general have the max pressure at which to mount Ana seat the tire which most people ignore anyways. The max pressure in the tire is printed for belt retention purposes , helping keep the tires from ballooning out of their footprint deigned shape and to avoid belt separations.

[@JasonWW2000]

@@luisbressantmtbseries.5232 How can a tire mounting machine know the max pressure of all different tires? It can't. There's way too much variety in sizes and load ratings. It is the tire manufacturer that knows what is the safe max pressure to seat the beads. So they mold it into the tire sidewall. A tire installer better not ignore the max pressure or else it could damage the tire. Then the shop is going to be replacing that tire for free. The shop owner will not be happy.

[@luisbressantmtbseries.5232]

I failed to mention that the standard max pressure when seating beads is 40 psi in the automotive passenger and light truck vehicles , while tires mar pressure stamped on the tire is determined by plies and load index.

[@wam7484]

Totally wrong. The tire sidewall pressure value is the pressure required to allow tire to achieve it's max-rated load capacity. Since cars typically have tires rated somewhat higher than the cars actual weight, the door sticker pressures are lower to suit the car's actual weight. Don't argue -- look it up on Google.

[@nas9971]

I dont usually comment but i wanted to make a note this episode, thank you neil and chuck for educating us! I love these explainers! ❤️

[@StarTalk]

Thanks for choosing to comment this time! :)

[@robertnobles8189]

Professional cycling has recently changed its view on tire pressure. They used to race at 120psi on skinny tires, relying on the rubber compound for sticking and comfort. Now they run bigger tires at lower pressure, like half that, for sticking and comfort. The importance of rolling resistance I believe is what started the move toward bigger tires at lower pressure.

[@crazysandwich]

Bike tech here , you're absolutely right ! 700cx23 at 125-145 psi is so hard, you actually lose speed because the tire instead of deforming to match the road, it bounces on the cracks and whatnot, you lose momentum there. Also, disc brakes. Rim brakes didnt allowed for bigger tires, clearance was an issue, and rim width was also limited by that. with disc brakes you can widen the rims, and then put wider tire whitout changing too much the profile of the tire, ''the roundness'' of it. A wide tire on a skinny rim makes it looks like a balloon, wich isnt great for cornering stability.

[@dummkompf]

@@crazysandwich ​ My bike made in 1950 has 40cm tires with rim brakes. Same bike that won the world grand tour (or something like that, I'd have to look it up again to get the name right) in the 50s. It was really funny to me when people in the road cycling scene started acting like this is a new and unconventional concept, or that rim brakes are somehow incompatible! lol admittedly there aren't many rim brakes that will work with wide tires, and none of them are high-end, but that's just because the high-end manufacturers have been so focused on skinny tires and so busy trying to shove their latest hyped up crap down everyone's throats in order to convince people to keep buying more and more upgrades that they don't really need. The move to skinny tires was driven by marketing hype to sell more products, and now people are amazed to find out it wasn't as wise as they thought.

[@crazysandwich]

@@dummkompf Yet the road bike with skinny tires got faster than the bikes of the 50's. Don't forget tire technology has come so much farther in the last 20 years. Things always evolve. I was strictly speaking of road cycling of the pas 30 years or so. But my point remains the same. Look at mountain bikes, in the 90's with canti levers and V brakes tire size would max out at 26x2.3'' for downhill tires, now the DH standard is 2.5 to 2.7 inches of width. Because disc brakes. The incompatible part is when you want to remove the wheel, if you have to deflate to tire to clear the brake pads even if you open the caliper, the tire is too big. That is the main concern. Also, if the rim is too wide the brake caliper would run out of travel, you loose modulation and power. you can make big U brakes like on your 50's bike. but then you end up with lousy braking no matter what, the bigger the ''U'' the more flex it has, thus less power. Rim brakes have their limitations.

[@ZimTachyon]

It is impossible to completely measure and understand the impact that Neil has on all of us who listen, and we will never see anything ever the same again.

[@snek9353]

Well I'm pretty sure this made me stupider, so you might be right.

[@Chimpur]

Coming from an auto mechanic background; you should inflate your tires according to the placard in the door jamb. It's a sticker that will tell you recommended tire pressures for your vehicle. Over inflating your tires will decrease the contact patch and therefore impact your traction with the road.

[@SoidSnake]

Sometimes this sticker is located on the fuel lid instead

[@keith726able]

After hauling the heavy load, you should let air out to get to your normal pressure.

[@bkbland1626]

Chuck is wise in knowing where his knowledge lies. Always.

[@dawnhansen7886]

Please continue with information regarding TEMPUATURE ❗️ Below freezing or hot summer air and how that affects tire psi. Oh please YOU TWO, I just love you guys ❤️

[@nickn780]

Neil, kind of wish you spoke about the “ply’s” and reinforcements within the tires. Brings it back to when you were explaining race car tires and banking of tracks/highways a few months ago. The physics of that is real cool also

[@philipsharman165]

I just subscribe to “Star Talk” and I am so glad that I did as Neil is my hero and him and Chuck are a great team 😂. Never stop laughing and Neil’s talks have made me a wiser human. Thank you 😊

[@BunnyKins1970]

Fantastic! There's so much more to this than at first appears. Next time I get a chance, I will try to work out the weight of my friend's car and I have now learned about hat sizes. 🤠 Keep up the good work! 💚🐇🐴💚

[@LaserSteve101]

You guys are Great!! Always looking forward to your videos ! Thanks from 🇨🇦

[@xpndblhero5170]

As an old-school BMX rider I really enjoyed this one because I know a LOT about tires and tire pressure.... My specialty at the local bike shop was assembly/building all the boxed and specialized bikes (BMX/MTB/road bikes/downhill bikes). I would build and balance the wheels for almost every bike.... Thanks guys. 😂😁👍🖤

[@allisoncarlin3124]

I can't wait to see the two of you again soon at the Star Talk show! I am counting down the days! 😁 Just a little over 2 months.

[@StarTalk]

Can't wait to see you there!

[@dinosaurandnapkin]

One of the best channels of KZbin.

[@kmarshall100]

Love this channel guys!! Where do we as common folk submit questions/potential topics of videos?! Have a burning planetary question but not sure where to post it. Thanks fellas!!

[@StarTalk]

Hey there! You get exclusive access to submit your questions for Cosmic Queries and Patron Only Q&As when you join the Patreon. Come check it out! www.patreon.com/startalkradio

[@merlinmagnus873]

You have to do the front and back tires separately. The weight of the engine in the front skews the numbers. A pair of 700X18 bike tires (super skinny race tires) tops out at around 110psi. 130 is asking for a blowout.

[@eranlevy4082]

Excellent explanation, thanks! tbh didn't know why wide tires need less air pressure - till now...

[@daviddavis9558]

Neil, great video! Now if you do created a video on combustion engines and explain boost with a turbo and/or supercharger. Go even further explaining an engine tune where you need to maintain a 14:1 O2 level by not going to rich or to lean in fuel with a side of engine detonation explanation.

[@sekaramochi1944]

Pure love don't pressure me Please please please never stop ❤️

[@jnajjar2687]

Thanks Neil, I was feeling a little down on myself. Yesterday I tipped the scales at the doctor’s office at 243, knowing you have nearly 20# on me is strangely comforting 😏

[@Milesco]

Heh heh... I was thinking the same thing! After hearing that NDT weighs 260, I now feel a bit better about myself. 😁

[@dizionsmith7615]

🗣TYRE PRESSURE!!! 😂🥂 0:18

[@everythingeducationsa5051]

I LOVE the explainers a lot. If only you can add subtitles and keep the measurements in metric system. That would be appreciated… All the way from RSA

[@wmtub]

That was pretty neat and practical too. Thanks!

[@scottburkettmichael8696]

Yes, as others have written, Chuck's WHEEL DIAMETER is 18". Depending on the tire manufacturer and model of the tire (when mounted on the "measured rim width"), the width of his tires (if they are OE) are probably around 8.5". In fact, any tire size, even though it has mm and inch measurements (e.g. P275/65R18), can be measured slightly differently when mounted on the same wheel between different manufacturers and models of tires. Tires are made within a specified range to be called a particular size. Then, mounted on a different sized wheel (e.g. 9") or even different air pressures will change the measured size.

[@rafaelvalle8989]

The funniest pair of the entire KZbin.

[@Puddymom]

“Oh believe me, it’s gonna flatten those tires” Lol so funny

[@joshuawittenbach6750]

1st thing I did was go find a measuring tape and measure my head after watching this explainer video. So cool!

[@JALNIN66]

I like this kind of every day, useable physics video. Would you consider doing a related video of how tires lose their elasticity with age and can no longer sufficiently deform to grab the road? There's a date code on tires and motorcycles are not recommended to run any tire older than 5 years. Paul Walker's tragic accident was caused by old tires on a classic car not having sufficient grip because they hardened with age.

[@RByrne]

Chuck's method of checking air pressure with your fingers was always the way we did it.

[@JamesTermy]

I really did learn something from this... Thanks!

[@wmtub]

That was pretty neat and practical, too. Thanks!

[@mistermonkey5842]

Boeing has an execelent paper on this very concept for the design of airport pavement structures. I've referenced it many time to calculate the "contact patch" of a given tire crossed against inflation pressure and load. Such a helpful concept.

[@petikan]

I didn't know where this discussion was going but I understood alot after his explanation.

[@juancdeliotejr5443]

Dr. Tyson I am a longtime fan and enjoy your explanations on science related topics. I learn so much from you and your discussions which usually lead me to research more about a topic. There is topic I don't see or hear you talk about, that is science related, and that is geothermal energy. If you have and I did not see it, I'm sorry, but if you have not then can you make a StarTalk discussion about it. Also, can you go beyond the basics and explore and compare it to other so called green energies. Thank you for all your work in educating the world about science!

[@missjayspeechley9213]

Thank you for this video, you just made my life as a cyclist a bit easier. So many times I've been at a petrol station using the air hose to top up my tyres, and there's always a motorist complaining that I set the PSI to the 60psi max (my commute bike runs 700c x 32mm @85psi) and I have to explain that as tyres get thinner, they need more pressure. Plus cars have 4 wheels with about a palm sized contact patch to distribute the wait, bikes have 2 wheels and a contact patch the size of a finger tip to hold them up

[@alanhehe4508]

Thanks for the chuckles, Chuck!! 😄

[@simplyblesd]

Been waiting for this!

[@chisquare5701]

It's been abundantly clear Chuck and Neil aren't car guys. How much a car weighs is critical information to motorsports enthusiasts.😅 I would say, it never occurred to me to use the contact patch to calculate my car's weight. That's why I watch this show! It's worth mentioning, though, that high performance summer tires,in particular, have considetsbly more stiffness in the tire wall than your typocal tire, which I suspect will 'lessen' the calculated vehicle weight.

[@HalfSkullSenior]

10:01 "get out of here!" 🤣🤣🤣🤣 He just got Science Slapped 🤣🤣🤣

[@fluid1614]

That's the coolest thing in the world. Going to try out the car weight measurement myself

[@joewindsor1119]

In car speak we call the area the tire covers on the ground the contact patch. For performance driving like on a race track you want it to be wide as possible and if you’re driving in bad weather like snow or rain you want it to as narrow as possible. Tire manufacturers also play around with tread design to aid with traction as well as the material used (some rubber compounds are stickier, some harder and so on).

[@max13499]

Good Morning. Love you both. Watching from BKK, Thailand

[@joemug4079]

Chuck! I’m with you! I barely get it too!

[@amolnikam303]

Best one, with so much info and so much laughter at the same time! ❤😂

[@SergiuMunteanu]

Great episode. So in the winter might be better to use slightly lower pressure to have more tire surface in contact with the road/snow for more friction?

[@ryanlucke88]

I like how the manufacturer labels these items in the driver door jamb. Fun facts guys!

[@l-Jeremy]

Chrysler 300 Tire Length is 5 | Tire Width is 8 5x8 is 40

[@muralidharrao2711]

Area x no of wheels x psi = weight 40 in ²x 4 x 36 psi = 5760 lbs Probably the contact area calculated is not correct. Due to the tread pattern, only a portion of the area may be in contact with the ground

[@thio59]

I like the chemistry between these two guys

[@johnelectric933]

You are a god! Thank you. I was somewhat of an expert on high performance tires for a while when radials were first being phased in. I never could figure out why the pressure didn't go up with load. That means the shape of the patch is controlled by the tire construction.

[@JMoroccoMisterBoy]

Dr. Tyson/Comedian Nice: Tks. much.

[@alexandrudanciu7874]

Good stuff with the hat hint and calculation of the car weight 😉😛- I'll try them both.

[@ctndiaye1]

Car tires= approx 32-35 psi approx. Certain skinny road bike tires, 100-200 psi approx depending

[@shawndorkoff3979]

U guys are awesome 😎

[@StarTalk]

Thank you 😎

[@Xray-Rep]

Wouldn't the contact area of a tire on the ground also be determined by how rigid the tire is which is dependent on the type of rubber used? For example, given the same pressure, a very rigid tire would flatten much less than a very flexible tire. Am I right?

[@tomv5782]

I think you are right. I have had several kinds of tire on my 4x4 offroader, some very strong (load range E) and some less stong (load range C), and the strong one takes much less air to achieve the same contact patch area as the 'weaker' one. So it's not just air pressure, but also tire construction involved. Mountain bike tires run lower pressure than racing street bicycles, not only because they are bigger, but they are thicker and heavier and the tire construction does more work in supporting the load of the bike.

[@craigquann]

Yes your right. But for this thought experiment, it's not really relevant. Say for example. A pickup weights 6000lb. You have 40psi in the tires. The contact patch will even out to the integrity of the tire plus the air pressure. Now load that truck up to say 8000lb. Now your tires still flex to even out the weight to the surface area. The tires integrity is already accounted for.

[@JennyInTheHighCountry]

Different types of rubber in summer tires vs winter tires vs off-road, etc etc

[@ItsOnlyGenjutsu]

Just popped in my feed at the exact time I closed the video I was on lol

[@scottburkettmichael8696]

And yes, the recommended air pressure is located on a placard typically on the driver's door jamb (less frequently on the passenger door jamb, inside the glovebox, or in the center console). The listed value is the "cold tire inflation pressure." Once driven just 2 miles, the pressure increases by 4 psi. So, if you have to drive 2 miles or more to check/add air, you want to add 4 psi to the recommendation on the car (30 psi becomes 34 psi). After the car has been stationary for 3 to 4 hours, the tire pressures drop by 4 psi by themselves.

[@Seraphim401]

This was wonderful.

[@rdspam]

Important concept - Psia (absolute) vs. psig (gauge). Correctly documenting this was Engineering 101.

[@Yebra92]

When Neil's explaining psi and square inch math, Chuck looks like Ed from Good Burger when he's nodding and reading the contract. "I know some of these words"

[@SteveC38]

Nice Splainer!

[@silva_579]

This isn’t factoring the sidewall rigidity of the tire, which can vary a lot, so these equations would not work

[@kydkaos55]

Cold weather is going to blow Chuck's mind!

[@justopeners]

Sweet, love it, I never knew that. Is Chuck going boating after the show?🤣

[@shafiqjan1474]

I watched and enjoyed on 3.14... Happy 🥧 day!

[@GeorgePap99]

First, omg I, like Chuck, also didn't care to know the exact weight of my car, but now I DO 😂 Second, thanks for putting the equation on the screen, because it was tricky to understand at first without looking at it (especially while trying to estimate the equivalent of psi and inches in my European head 😂).

[@fixbertha]

Tires have grooves in the treads, those grooves subtract from the length times width calculation. You could get a close to the actual contact patch area by measuring the raised tread area in a given section of tire (e. g., 6 inches of circumference). Multiply that area by the length of the contact patch of the squished tire and that would give you the area of the contact patch. You can tell that Neil and Chuck aren't too familiar with cars and SUVs. Doesn't matter, mostly a good explainer, and I'm a big fan.

[@pawewielgus2105]

Does the car tire contact patch is a square shape? And how much (if any) does the bicycle tire pressure change when a rider sits on a bicycle, like some kind of auto compensation the contact path area and pressure for the changing weight of the system?

[@TheDwightMamba]

I swear this is relevant to the subject matter. Scottie Cranmer has a KZbin channel where him and his buds shoot BMX videos. Often they play a trick competition called BIKE. They take turns setting tricks and if a rider doesn't match the trick, the rider gets a letter. My favorite version of BIKE is called Wheel of Misfortune. The rider calls out his trick before spinning a wheel chained to a bicycle crank. The wheel has a bunch of unfortunate handicaps and the rider must incorporate whichever the wheel stops on. Some examples... forward "Chicago" style handlebars, backwards forks, wet shoes, shoes on wrong feet, backwards seat, switch bikes with the nearest rider. Some really creative stuff. My favorite 2 misfortunes deal with tire pressure. 25 PSI and 125 PSI. Park riders tend to ride in the 70-90 PSI range, so both of them make almost any trick they call turn out sketchy. If you like bikes and fun, there isn't a better channel. Thank you for reading all of this. My worlds converged and I had to chime in.

[@timknight5105]

Love Chuck!

[@PilotVolunteer]

Yes, Chuck is correct! I did the same when I was young with a bicycle

[@klumaverik]

Omg It's so cool to be living at the same time as these two awesome people. 🥰🥰

[@MrMonsster]

I so love these vids, but boy oh boy would I like them even more when measurements are in metric, or at least metric calculations in overlays in the video. I'm having a hard time keeping up recalculating. :) Sincerely, a dude from Amsterdam.

[@Nightcrawler333]

Great video. I'm a motorbike rider and I can say this is very important knowledge for anyone who owns a vehicle. Can you also cover other fascinating mechanics of motorbikes in your future videos?

[@jag731]

Never fails.. using wonder, science and comedy to once again gain knowledge. Alas - another #StarTalk Tshirt .. "Make America HAT Again". 🤠

[@MikkoRantalainen]

9:00 Car tire markings are very funny because those numbers are total mess of imperial, metric and percentage units. For example, "295/45 R18" literally means 295 mm wide, 18 inch wheel diameter and 45% extension from the edge of the wheel to the outside of the tire when the percentage is computed from the width (295 mm in this example). I bet Chuck does not have 18 inch *wide* tires in his SUV. He might have 18" wheels, though.

[@LuisGomes-jv2kc]

Hi there... Big fan of your shows... I have a question... Can the rings of your fingers be calculated in the same way? Circunference/Pi ?

[@mariofilipereira]

For our American friends, European hat/helmet size is straight out from your head circunference in cm: 58cm perimeter = size 58 59cm perimeter = size 59 and so on..

[@operationhotshotinc.6887]

This is was pretty cool

[@genoquichocho3492]

Don't get the pressure off of the sidewall. Your driver door has the recommended pressure to also include the spare tire pressure recommendations.

[@tomo-tu]

Saw a video of the trek over snow . Large tire less air. Once used chemical ignition to inflate tire.

[@AceSpadeThePikachu]

Now we need an explainer on how bicycles stay perfectly balanced on just two narrow tires without toppling over (except for clumsy clods like me.)

[@tmeyer2022]

This is not a correction, just a short addition to the explainer. Farm or industrial tractor tires may, for specific use, be filled with an anti-freeze solution to increase tractor weight and effective tractive pulling force. Tractors, so equipt, would be set up for dedicated use (filling and/removing the water mixture is laborsum.) During the early to mid 1900's, adding weight via the anti-freeze mixture was thought to be desirable because increasing the weight of the tractor allowed pulling larger farm equiptment with less wheel slippage. That increased tractor weight was later shown, by scientific agricultural studies, to increase soil compaction [which is not conducive to plant growth, vigor, and eventual crop yield]. 🤓

[@AB-ye7bw]

Chuck is the best!

[@MaryAnnNytowl]

Well, I knew the air weight/tire pressure thing, but at least I learned something! I never knew how hat size was determined, but now I know. I didn't waste the day! ❤️❤️

[@joelb8653]

Fun topic, a MAP sensor on car is an acronym for manifold absolute pressure but it measures vacuum which is obviously not absolute. It should be manifold gage vacuum.

[@russbell6418]

@joelb8653 Nah, it’s correct. Absolute pressure includes the additional 14.7 psi from vacuum up to atmospheric pressure, because that is part of the air pressure necessary for the computer to calculate fuel volume. Some gauges in industry are labeled psig or psia. Gauge (ignoring atmospheric pressure) or absolute pressure.

[@charliew9515]

One thing, in my experience (driving wheel tractors, combines and crawler tractors), farm vehicles don't have wide tires so the can run over crops more gently; they have wide tires because they are off road and need traction in these conditions. On another note, as an engineer, curious how much the elasticity of the tire affects its pressure in real world conditions.

[@dramfan25]

What about the load / ply rating? Would that not effect the rigidity of the tire itself and therefore the amount the tire would squish at any air pressure?

[@vincentvergara2728]

Please do an episode on bicycle road tires because the current cycling trend is that wider tires and lower tire pressures have less rolling resistance.

[@sketchtheparadigmyork1217]

Ooookaaaay they got a Mr. Editor to add nice little visuals nice

[@raze4789]

Often this is referred to as "contact patch" more is better for traction and floatation. This is why often when off road you reduce tire pressure. Also the opposite applies to road driving, less contact patch = less rolling resistance, improving economy. Also why electric vehicles will have skinny tires.