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- เผยแพร่เมื่อ 8 พ.ค. 2024
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It’s 2021, and we’ve come a long way since Carl Benz patented the first car in 1885. Teslas can hit 60 in just 2s, F1 drivers experience more Gs than an astronaut, and there are road cars - plural - that can go 300 mph. None of those amazing feats would be possible without the one part that actually touches the road: tires. Today, we’re going to figure out the secrets behind tires’ grip, why there’s so much variation in what seems like a pretty simple design.
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I actually asked the same question to my Dynamics professor a couple weeks ago. it's because Mu isn't a constant. Mu concentrates all the factors that go into two surfaces gripping each other all into one term. If Mu were to be expanded you would see that it depends on surface area in contact, material properties, external conditions, etc. In most cases where the friction equation is used, you can assume that Mu is correct within a certain tolerance. in the case of car tires though, there's a lot of factors that cause Mu to vary wildly and so in this instance the friction equation is used as an approximation at best. Love the vid
Asked my dynamics prof the same thing when I took it haha. The other factor is that the traction a tire produces does not actually increase linearly with the vertical loading. Essentially, the coef of friction decreases as the stress in the tire increases. This means that lowering the initial stress in the tire(larger contact area) will produce a higher tractive force under the same loading(the loading ceiling before mu decreases is raised). That is especially true in high downforce applications, but there is still significant load transfer from cornering.
@@tristanhanley8741 oh nice! Thanks! I’m majoring in aerospace and dynamics is kicking my ass so I’m glad to hear the same thing from someone else haha❤️
Took the words right out of my mouth..I should get the shirt 😜
Yep same exact story for me when I was taking those courses 10 years ago. Me being a gearhead helped in some areas but that was one where I was at a definite disadvantage in terms of having to ignore or unlearn some preconceived notions and mental shortcuts for exam. My instructor brought up pretty much the same as yours as well as pointing out that for the sake of exams and theoretical calculations you're always assuming a perfect interface, but of course that isn't the case in reality even on a prepped race surface, and by going with wider tires you can think of it functionally as if you're casting a broader net to achieve that optimal surface to surface interaction.
@@tristanhanley8741 So would that make the equation a f''(x) of the frictional equation, similar to how acceleration is just the second derivation of position? or maybe its the 3rd derivation such as jerk is? Thats my initial guess.
I love this episode, it brings me back to science garage with Bart. "Don't tell my wife." Lol
this episode is giving me some science garage vibes lol (still miss that show 🥲)
samee
holy shit a verified channel that isn't a bot as one of the top comments
It's because of that show I started watching donut.
Bring back Bart!
What happened with Bart??
I love Jeremiah, he's got to be the BEST at explaining techy things all in layman's terms while being fun. Great presenter. I come back every week for all Donut's videos, but he's my favorite to watch.
Mechanical Engineering and a Masters in Biomedical Engineering. So he has a knack for it.
He wastes too much time making useless jokes and not being precise to the point.
“The only part of the car that touches the road”
My lowered shitbox: *Frame proceeds to hug the ground*
Please tell me you bought it like that
@@sufferr2914 I actually did
@@twostrokeproductions757 thank god
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@Leonardo Santuario thanks man. I appreciate it
Actual Tire Engineer here: the reason why you can get more than 1G grip and the reason to run wider tires on a race car has to do with shear strength!
When the tread rubber goes into the peaks and valleys of the road surface, your extra grip comes because you have to physically shear off that portion of rubber to move the tire off that spot, the hot tread rubber has penetrated into the grooves & crevices in the road surface so it tears off rather than slides across. That’s why burnouts and donuts leave black marks, it’s rubber that was sheared off. So why wider? Because as you put heat into rubber, it is easier to shear, so a wider tire distributes the heat better but also has more individual peaks and valleys to shear pieces of rubber off.
My quiz for you Jer: how does a tire keep the wheel off of the ground?
Why doesn’t the wheel just squeeze the sidewall down until it is touching the road like pinching a balloon? You can compress the sidewalls by hand, so why don’t they just squeeze out of the way when the car is loaded on it?
This makes a lot of sense. I had a feeling it was to do with shear strength and immediately though of increased area therefore reduced stress, however I quickly debunked myself because Fz = P*A and obviously the pressure and weight on the tire are assumed constant therefore the area does not change amount, just shape. Could the fact that the contact patch become wider and less long with a wider tire also help with grip because more of the area is contacting fresh concrete, not rubber filled "dirty" concrete? The explanation on local heat leading to lower shear strength makes lots of sense!
because of the tires air pressure. and a flat tire can never go below atmospheric pressure you would have to vacuum it out
As was explained: in addition to the frictional force, the tire is also pushing itself off these small peaks in the road. This is not a frictional contact but simply a "stuff pushing itself off other stuff" contact. Normal force is directly transferred between the tire and road in forward direction.
A wider tire is the only option to increase the quantity of little mountains the tire can push itself off and therefore increases the overall amount of grip.
The mu value for grip is just a good enough approximation for normal everyday (I.e. Not drag racing) use.
Sorry for lacking some words. It's really hard to explain this stuff in a foreign language
on top of tire construction and so fourth a balloon is made to stretch a car tire is not a drag slick is closer to a balloon concept as it starts out as a wide tire and the higher the speed it grows taller reducing width to gain diameter it is also used as a gearing aid i could go on and on
on top of all of this sorry one last thing a wider tire makes up for a larger tire in diameter and its really the end of the story there its to keep the tire from having to be 40 inches tall to keep a contact patch on the ground the same as a shorter tire that is wider carry on
On the topic of wear bars, one thing I think is cool about the Continental ExtremeContact DWS tires (which are great by the way) is a built in wear indicator. There's a D (dry), W (wet), and S (snow) imprinted in the tread blocks that will wear out in reverse order. When the S is gone, it means they aren't ideal for snow anymore. Then the W wears out, meaning they no longer are good in the wet. Then the D, obviously meaning dry traction is no longer ideal. It's just a cool little system they have that simplifies reading what stage your tread wear is at. Slick bit of kit if you ask me.
I agree this is brilliant. I wish it was standard across tires.
14:10 wider channels between lugs (particularly on more offroad focussed tyres like mud terrains) actually help the tyres to self clean when driving through mud and sand so that when the next part of the tyre becomes the contact patch it isn't full of slippery mud. All terrain tyres tend to get filled with sand or mud which does help on soft sand but is completely useless in mud as they don't self clean. The wider channels also help the lugs to deform around rocks when they are let down to give the tyre as large a contact patch as possible when driving over rocks and the like.
I can't wait to watch this in college as apart of my course
Wat course will u be doing?
I swear the last 6 months of watching donut makes me feel like I'm halfway through a technicians course
@@tinashemoalusi8920 mechanics just started in September and all ready seen a past donut video
exactly what im doing rn
Seriously these videos are great for learning how to apply engineering principles
Engineer here. The equation Friction = (coefficient of friction)*(Normal Force) doesn’t tell the whole story.
As the normal force increases, the coefficient of friction actually goes down slightly. This explains why body roll causes the car to lose grip. More weight is put onto the outside tire, but the coefficient of friction of that tire is now lower than what it was before, which means that the total force that stops you from sliding decreases.
The reason why you want wider tires is twofold. First, wider tires can absorb and dissipate more heat that narrow ones. So if you’re generating lots of heat from racing for example, narrow tires would get too hot and overheat, causing decreased traction.
Secondly, if the same force is distributed over a larger area, the pressure the tire feels goes down. This makes the coefficient of friction go up, since each tiny section of tire is feeling less weight on it, because there are more sections to distribute that weight.
TLDR; more weight, lower coefficient of friction. Distribute that weight over more surface area, coefficient of friction goes up. Higher coefficient, higher grip.
Looks like we found the smarty pants
So instead of thinking of it as force pushing it down a better way to think of it is the pressure pushing it down?
@@Stevethe11th sort of. The formula is still F=mu*N, but think of mu as a function of N and surface area (and temperature)
Yes and no. Normal force is a multiplier of mass. So a heavier vehicle will have more traction than a lighter vehicle on the same tires. It just takes more energy to make it accelerate and decelerate.
this is the first correct answer I've seen. good job
side note, you shouldn't confuse body roll and weight transfer. while they're related, they aren't the same thing.
second side note: a bigger tire isn't always faster. while it can give you more grip by allowing you to run a lower pressure for the same load carrying capacity, it also means more mass to accelerate out of the corner.
This chanel has taught me more about my car than any class I have taken and has saved me so much money from getting riped of at dealerships. Thank you!!
ALSO DO MORE OVERLOADING STUFF! Nissan frontier would be nice! Or the AUSTRALIAN Offroading seen
If we’re talking about Top-fuel dragster’s they use an extremely low tire pressure (I think 5-10psi)so they can use the affect of acceleration on the low pressure to change the circumference during acceleration and use this affects as a sort of gear box, when the car the launch’s the circumstance is the biggest it’s gets and along the run the circumference gets smaller to change the supposed gear ratio through the tires.
Absolutely fascinating stuff.
(I think top fuel dragsters officially only have 2 gears in they’re gears box)
Zacharia Weisman : You have the getting bigger vs smaller thing backwards. It starts off small then at speed it increases diameter due to centrifugal force. It does in effect change the final gearing.
wider tires aren't making any single point stickier they're just allowing a larger distribution of the forces. lower force over a given point will result in less slip.
To expand, the amount of force per square inch is less such that the rubber won't deform as much and fail at the contact point.
As well as being able to use a softer compound with similar tread life
To put it in even simpler terms, for a larger tire you'll get a larger contact patch. And while the contact patch is horizontal, the shear force is what matters here. So, the actual ability to grip comes from not just the theoretical friction force, but also the ability for both surfaces to remain in place. If you have a smaller tire with the same forces, it's more likely that the tire or ground will start to break down. This can be seen most closely with the grooves made in roads by semi trucks, as they are heavily loaded and are able to quite literally push the asphalt away as opposed to simply pushing off of that asphalt.
On top of all that, many of these tires are also made to bond to the asphalt. More patch means more bonds, and more bonds means more resistance to sliding. This translates to a higher real world friction coefficient.
This is all too complicated for me. Someone please explain to me very simply, why does a road bicycle tyre (think tour de france tires, 2-4cm wide) have such good grip, even though it's so slim?
If Jeremiah taught a high school science class, those kids would learn so much!
At the same time, allowing Jeremiah to influence young minds..
I know what you mean 😉
That's not want the world needs. If he was just a science class teacher only a few would learn. Now we ALL get to learn and he influences young minds all over the world.
Jeremiah would be the teacher from the "Whoever threw that paper..." vine
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please be my physics teacher Jerry, you would be such an improvement
Very informative I use to change tires and now mostly alignments and good tires makes me happy
Since Jeremiah's video on the Ducati V4R, I've been a sucker for his videos ever since, especially technical videos like this. Great job, Je.
The reason why drag racers have wider tires is to introduce more points for the tire to enact force on the "peaks" of the road surface. In an introductory physics course most of your teachings and understanding is on a single point of contact, or particle. So the friction equation F_f = \mu * F_n, can be scaled according to however many particles, or instances of contact you have. That's also why drag racers use softer tires, and often deflate them, so than can introduce more instances of contact to the road/track surface. For example if you have a tire so small, where it only makes contact with only one peak in the road surface, even in a heavy vehicle, the force of friction will still be relatively small compared to it's weight. It's like have only one one person push a brick wall, but if more people push the wall, eventually the wall will topple. You also cant forget there are two different types of friction, static and kinetic. Static, for when an object is usually at rest and trying to move; and Kinetic, for when an object is usually moving, and is trying to stop. Coefficients of static friction are typically smaller coefficients than kinetic friction, meaning it's harder for the weight (which is "equal opposite" of normal force) to act on the tires regards to get gaining Grip.
-UCF Aerospace Engineering undergrad
Also, I love you guys!
static coefficient > kinetic friction
Its the same thing we do when we go mountain biking, less air more surface area more speed and control downhill 🤙🏽
Thanks for the info
You won that t-shirt for sure!
In layman terms, more surface area to contact with... just as intuition would say. Maybe there is nothing that accounts for a definite area in an equation somewhere, it's essentially still the same thing, in a roundabout way. More points of contact literally translate to a bigger surface area. That's quite literally what an area is, a lot of discreet points next to each other. Deflating a tire just increases the contact are with the road as it sags more under the same load. I understand what you say but it seems the question is more philosophical than describing reality.
This is not exactly true, theoretically in the simple friction formula area does not matter. Even if a mack truck only contacted one peak, the available friction force would be the same. The answer to the question is the coefficient or friction is not constant with tires compounds. The coefficient itself is inversely proportional to surface pressure. That's why the simple physics formula you learn in your undergraduate generally fails when you consider tires. With the simple formula there is no reason that a truck takes any longer to stop it than a motorcycle. ( Mechanical engineer )
I feel like Jeremy is feeling more and more like the family, and it's great to watch.
Love the Donut family.
That's what they are
It's Jeremiah, or jerry
jerry's my favourite
I read this in Vin Diesel's voice
Dom approves
Until you and grandma are walking home together.
Anyone else miss the old B2B where James would get an interesting car and go into detail about it from front to back. Love the series that Jeremiah does though!
I want both
Just go watch Doug's channel ;)
I miss the LIGHTNING!
I like the ones where James cries because he's moved emotionally. Realy men aren't afraid to show emotion. Love ya James!
Actually, not trying to throw shade, but James is my least favorite presenter, because he is always trying too hard to be over-demonstrative. It seemed very natural in the early vids years ago, but now days it comes off as trying too hard. Where Jeremiah comes off much more naturally most of the time, but he also pushes into that "James Zone" from time to time. But a lot less than James actually does. Either way, I like all of them. It's just in varying levels.
Thanks Jerry, the same question you said in the end I had in my mind the whole video.
I love your videos
I laughed really hard seeing the Subaru hit that pole in the snow when talking about grip coefficient and water. Just perfect
Everyone thinks AWD and Subarus are some kind of magic in slick conditions. They're not, the just have a boost to acceleration in low traction situations, which MIGHT help you get unstuck. It does nothing for braking or turning.
@@Ididerus it’s more stable than rwd at least. But other than that, it’ll skid like any other car. I’d argue fwd is slightly safer in slippery conditions anyway in terms of handling.
They dont turn for crap in the snow. Until it finally goes into snap oversteer 5 seconds after flooring it
@@Ididerus Veyron: Just add water please.
@@devandrasimanjuntak1646 i bet these tyres reminded me a lot to hypertrains.
The answer is Hector is going to be running 3 Honda Civics with SPOON engines. And on top of that, he just went into Harry's, and he ordered 3 T66 TURBOS, with NOS. And a MOTEC exhaust
Lol Spoon with Turbos😆🐤
F&F
I never understood the last part, MOTEC never made exhaust systems lol
@@WhatZitTooYaaa i think thats kinda the whole point of that line. Dismt want too include any real companies other then nos because nos is a brand and its well shown off in FF so they either sponsored or idk. The spoon engine is real but its not actrually called a spoon engine. I think its a very specific honda crate engine(not made by honda) and their like 30-40k and dont exactly make alott of power but their made too handle more power then any axle you can fit in those cara coupd handle😂
New subscriber here, just found your channel yesterday. As a workshop owner, I love your contents and all these are being quite informative and useful dude. Keep doing the great, support from Malaysia 👍
s/o to this channel. i’ve never been all that into cars, but you guys make it so easy to understand & it’s so enjoyable
when Nolan is just drilling at the table during the "Mo Powa Babeh" Ad. LMFAO
Him throwing the vulcan hands up while saying "messaa loved the new star wars movies" in Jar Jars voice made me die a little inside lol. Our beloved childhood franchises are so lost.
About lost my mind over confusing the two.
The Spock / Jar Jar crossover film needs to happen now! Com'on Disney and CBS play nice for just this one time!
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Beloved garbage
@@recreant359 Are you dumb or just saying all star wars is garbage?
Amazing series.
Honestly I'm not even into cars really. But this show and channel show present car culture in such a different way, that it's really attracting outside audiences.
Great combination of information (that would normally have hurt my head) and humor (that prevents the headache). Well done.
Answer: wider tyres increase odds of getting the maximum friction the surface has to offer. Also lowers pressure per unit area which lowers overall wear.
I think your right!
I am not a engineer but I did read the other comments and they look right when I looked what they said on google. Basically the reason why larger tires give more grip is because the world is not perfect and there is sometimes gaps between the tires and the ground, and making them larger gives you more chances to touch the ground. Though in a perfect world a small tire and a large tire would have the same amount of grip.
no that's not actually the case. it's because Mu in the friction equation is a variable not a constant and surface area plays a huge role in determining the value of Mu
Uh, depressuring your tires increases wear, the sidewall isnt meant to take excessive loads when under aired, you can risk bubbling or debeading because your tire isnt keeping its shape
@@pleasedontwatchthese9593 The most used Racing tires are a slick, meaning no tread. Just a giant contact patch. Formula 1 uses either slicks in dry conditions and a lightly treaded pattern in wet conditions. If it were a perfect world we would all be running slicks optimizing grip to a n almost 100% degree of contact.
@@ultimatum117052 He's not talking about the air pressure of the tire, to my understanding he is refering to the same pehomena that makes snowshoes work. Larger footprint = weight being distributed on a larger area.
If you have a 5 square inch contact patch and your ''car'' weighs 100lbs, you apply 20 lbs per inch on the ground of pressure,
if you now have 10 square inch contact patch but the same weight, you now apply 10 lbs per inch. so in that sense, the tires would last longer. If that makes any sense lol
For the question at the end:
(Edit: provided clarification after initial response).
"I believe the reason is that the frictional force equation tells you the force at which you exceed the static force limit and would start to slide into a kinetic frictional state (which has a much lower coefficient uk). It essentially defines an upper limit of what your system is allowed to do before you slide. So, when you have wider tires it helps keep the contact patch wider and thus reduces the force on any given point. With less force on any given point you are more likely to stay under the static frictional force limit provided by the equation. If you had a skinny tire all the force would be spread out over a smaller area, so you can more easily apply enough force to exceed the static frictional limit.
Hopefully that makes sense! I am a bit rusty on my kinematics."
After reviewing a bit, I think the key is that F=u*N is deceivingly simple. It is more accurate to say that F=u*Sum of Normal forces being calculated at each point where the tire is making contact with the road. Thus, your frictional force will increase with a wider tire, as you have more little interactions culminating in a larger frictional force. Your u value could stay the same if you use the same compound, but the number of normal force interactions will be higher on a wider tire.
Go home. Lol you have won
TL:DR bigger tire, bigger contact patch. That's needed because of the power that a lot of those cars make.
I like your name
Checks out
you win, hope donut thinks that too
Incredible stuff as always. Thank you
Wow! So much info and production quality.... you've taken this to another level.
he's a great reader.
"You could be eating your Jungle Nuggets. And a guy could have a seizure. It could happen. It's why I go there."
...me too
wtf
Jeremiah is truly a man of culture.
That place is real?
@@danielaguilar1125 Yea it is, I haven't been there in a while
Answer: The classical model of the friction coefficient, or it's "formula" does not apply to tires. It's good for a broad sense of how friction works but tires have many other variables to take in count than just Ff=(Mu)Fn. Pressure, angle of turn, temperature, etc. There's a difference between coefficient of friction and, more specifically, tire load sensitivity.
Hehehe, "load sensitivity"
I wonder what would be the full representative formula for it...
If this dude didn't steal this comment he should win.
@@james4wd236 AGREE!
If I remember correctly, rubber also has shear strength which means that for a given sideways force there's optimal weight per cm² where the rubber can handle the sideways load without tearing. Cases where using wider tires improves performance are usually the cases where the surface of narrower tire is sheared away due exceeding structural integrity of the rubber.
Another solid episode!
Thanks Donut team!
That cat in the tiger costume and sunglasses(around 14:55) was extremely adorable
My (hopefully) educated guess for the last question regarding the absence of surface area in the formula of friction force goes like this. It does not influence the linear movement grip, but it highly improves cornering grip, the same way in which wider bodies improve cornering stability. A good way to visualize these scenarios is to take some exaggerated versions of the extremity-scenarios: imagine a car with bicycle wheels. When cornering, a narrow tire will bend towards the inside of the corner (relative to the rim), moving the contact patch towards the lateral side of the tire, and rendering the highly engineered middle of the wheel useless, since it loses contact. A wider tire will have a much harder time bending like that, since it is supported by forces further apart, thus maintaining the contact patch in the area the tire is designed to have it. Same reason why low profile (hope that's the correct terminology) tires will perform better when cornering on smooth surfaces: bending is limited. A seemingly counter example would be the high profile tires of Formula 1 cars, but they are smooth everywhere, anyway, so even if the contact patch moves to one side, the road will still see the same type of tire surface, and would behave the same (assuming same chemical composition on said surface). That's my two and a half cents, hope I'm not way off. If you got this far reading my long comment, might as well leave me a like to show that you agree ;) Great content my dudes, love your vibes and appreciate your powerless communication which makes you so much more relatable and enjoyable. Peace out.
Edit: Uziel Lavine's answer seemed pretty persuasive as well, for the microscopic aspect of it. As a macroscopic view, I still think my point stands.
I see people posting their backgrounds, I'm a physicist engineer. :)
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This is true but he does also ask in relation to ‘drag racers’. They generally don’t require cornering at high speeds as they are straight line cars. From what I remember hearing from my mechanic mates, a wider tire profile for drag cars are generally to benefit ‘off the line’ response. This is also why the back tires are much wider than the front tires. To accelerate, the engine must apply force to the driving wheels (which with most drag racers, is RWD). When you accelerate, weight transfers from the front of your vehicle to the rear.
My mate likened it to a sprinter launching from running blocks. The sprinter will ‘launch’ faster because the running block is providing a resistant, otherwise theoretically the sprinter would shift slightly backwards. A wider wheel in a way acts like a running block. More friction, more grip, higher acceleration which in essence is what drag racing is about.
surface area gets neglected from the coulomb friction model taught in high school or freshman physics because with linear and isotropic materials (ie steel) it doesn't matter that much. visco-elastic materials like rubber have a pretty significant pressure dependency on grip. more contact area means lower average pressure for a given total normal force and hence higher grip. that's why slicks work. or why ultra high performance summer tires have pretty minimal tread features. or why larger tires can be made to work better.
drag racing doesn't have corners. Bigger tire= more grip in drag racing.
I would love to see B2B on “World of Outlaws” Sprint Cars
Bigger tires typically means you can run more tire pressure while having the same footprint area preventing tire shake and maintain control of the dragster. You guys are great over there at donut one of the main reasons I have learned so much about different stuff in cars
But old cars with thin tyres have like 80 psi whereas modern tyres have 30.
Love the videos guys, I'm definitely learning a lot. Have you guys done a video about why the auto industry now recommends rotating your better tires to the back?
Nobody likes a fishtail.
“Goodyear was arrested for owing some guy money”
Me who had intoxicated ox riding: my disappointment is immeasurable and my day is ruined
So, there are a few reasons why, first of all larger tires have a lower mass distrubution per area unit therefore allowing for lower presures wich lets the tire to flex more and adapt better to the road. Second, having more area is good for heat dissipation and a lot of heat is generated in those types of race.
Very informative for sure!!!! Love it
One of my favorite episodes so far
A week ago I realised I need new tires and kept researching the best options for best possible grip and this helped me more than anything
I just got the continental DWS06 tires and it's rained twice since then I've purposefully tried to lose traction to compare to my old. I highly recommend them they are very grippy
@@user-gk2cg2th9h had a look and they come in just the right size, fairly cheap too!!! Cheers
I believe the answer to the friction circle riddle is because there's chemical reaction between the tyre and surface causing grip too.
Amazing video, super well researched and animated. One extra point about tread design is that it plays a large role in noise, which is why the shoulder blocks are never even. Noise is basically air pumping out of the tyres tread and they can break that up.
Oh and the main reason asymmetric tyres exist is because it's easier (and cheaper) for the OE car manufacturers for mounting when compared to directional, as least I understand that was the original drive.
I want to go to that animated monkey cafe. I now live in Salt Lake, sounds like it's worth a drive.
The part regarding noise and air may be atleast somewhat true for street tires but I know super swampers make noise because those nubs are hitting the road going 60 and have no choice but to make noise, the unevenness is just apart of the off-road gripping design, if they were even it'd make them quieter. Don't think it's an air pumping action, suppose you could also say all sound is just turbulent air hitting your ears, so split the diff?
Caz
Hey! It's Jonathan Benson everyone! This guy is an expert!
We just got Collab-ed!
Funny enough, while watching this video. I was thinking about your channel, and how cool it would be if they brought you on to explain things.
donut is just brilliant love u guys keep up
Always a huge fan of this stuff.
When creating a good compound for acceleration, softer compounds are favoured however an issue with softening the compound is that it will no longer support the weight of the car. To alleviate this, widening the tire and potentially using different compounds in different areas, along with stiffening the sidewalls helps to increase the weight the tire can support as well as improving cornering performance as the tire also experiences less roll. This widening gives a larger contact patch with the surface also, again helping to even out irregularities in a surface, increasing stability and grip.
Correct. You beat me to it.
Physics question answer: the road and the tire are both uneven/imperfect surfaces which mean they come into contact with each other at multiple points over the contact surface area (explained by the peaks and valleys example in the video). Each one of these points experiences the full force of static friction. Since each contact points independently experience their own frictional force, it creates a cumulative effect across the contact patch of the tire, which is why "more surface area equals more friction".
Agreed! If the contact points were perfect rectangles between two surface of homogeneous properties, the area of the contact surface wouldn't matter. With how the road is, and how compliant the rubber is, the larger the tyre, the more chance it has to find a spot of high friction. I'm assuming you can see this effect in reverse with rolling friction (in which theoretical tyre size would not have an effect but real tyres do)
I'm fairly certain this is the majority of the answer. Friction does not go up with surface area, but mechanical grip DOES.
I don't know if people tell you this a lot, but I really appreciate these informational videos you guys put out.
I love that you put actual hieroglyphics on the tire's sidewall for the animation. Yeah!
I'd say for the tires, and by what I remember from physics classes, the formula doesn't have the width component in it simply because it is considered as if the tire was touching the ground on a line, aka, something that has no area (Because it is a line of points, and a point has no surface area), whereas in reality, because of weight and different forces applied on the tire, it will flatten and the contact patch will go from a line to a rectangle.
Since mounting a wider tire does not increase the size of the contact patch, only its shape - the reason for more grip is that because the contact patch is wider and shorter each piece of rubber is in contact with the pavement for a shorter amount of time. As a piece of tire is at the limit of grip on a piece of pavement, the grip generated is dependent on how much it is sliding. The more it slides, the less it grips and it will slide more the longer the rubber is in contact with the pavement. So, since each piece is in contact for a shorter amount of time, but there are more pieces, you get a net increase in grip.
Incredible well done video
I worked on tires in the early 80s. We had a lot of radial tires that would separate (steel belt separation) caused by changing the rotation of the tires when they were rotated.
The friction answer: Larger surface area reduces the pressure between them. Pressure = F/A, so an increase in friction area is offset by the reduction in pressure. This means that only the frictional force between them matters.
correct answer i first replyed incorrectly with F=ma and forgot that a is accseleration and A is area
A lot of people have already attempted to answer this, and I might just get lost among the other thousand comments, but I'm learning about this in a physics class this semester so I thought I might take a crack at it. The reason that F_f (force of friction) is not dependent on surface area is that when surface area is larger, the weight force (F_g) is spread out more across the surface area. Essentially, larger surface area means less weight per unit of area. However, the reason that drag racers use larger tires (I think) is that on a drag course with a treated surface that has whatever sticky substance on it, friction is not the only force acting between the tire and the road.The adhesion (ability to stick to other things) of the sticky substance is very high, and when there is more surface area on the tire, there is more surface area for the tire to adhere to the sticky stuff. However, I don't know too much about drag racing so I may be wrong about sticky stuff.
That's all makes sense, but that leads to the question why normal sports cars or race cars have so wide tires?
Why are the Corvettes tires so much wider than a Honda civics tires?
I have a feeling it's about the tire wear. for example, if a 1in by 1in section of a tire can only take a certain amount of force then on a skinny wheel you will exceed the limit of the 1in by 1in section. but on a wide tire, the tire doesn't exceed the maximum amount that section can hold because there is physically more surface area for the tire to hold.
frictional coefficients are not constant between two materials. there often is a pressure dependency. for rubber a higher pressure means a lower coefficient of friction and less grip.
adhesion is one of several friction mechanisms present in tires. drag tire tread compounds have friction coefficients much higher than 1.
@@bolt5564 I think that’s more to do with use cases. Wider tyres are a huge draw to fuel efficiency and even some power, so unless the benefit of extra grip sometimes isn’t worth what you’re losing
Wider tires are able to use softer compounds, therefore have a lower coefficient of friction. So a drag car has extremely soft and wide tires with a really high coefficient of friction. As the tires get narrower, the coefficient of friction goes up due to the compound getting harder.
In regards to cornering, the wider the tire, the stiffer the side wall leading to less rolling in the tire.
Real great content. I love it. Hard to cram so much information about tires. There's much more to know about tires. Gotta do a part 2. Load index, ratings, LT tires, and! Those sound dampening tires. But this is a great vid to give people knowledge on what tires are about. ❤ to Jeremiah and donut media
μ has surface area in it. In general the coefficient of friction is just a rough approximation. It's a model for how friction would affect an object and models have limitations.
As you have said, road conditions can be varied, so to estimate we just take averages. Different tire widths act differently as well. Differently shaped contact patches and all that.
Tire Test Engineer here. I will say this was a great and informative video, love these from Donut Media! Tread pattern design is not just for looks though, that does come into play some, but the shape of the tread pattern will be driven by tire noise too. A passenger car tire is designed to minimize road noise while a wet race tire is designed for maximum water evacuation. Having tested about every tire type, a wet race tire does the best job at evacuating water from the contact patch, but they are extremely noisy tires in both wet and dry surfaces, this is comparing slicks and wets with the same compounds and constructions. The average customer would not want a tire as loud most of the wet race tires.
Keep up the great content!
Tyre test engineer, go test tire, stop wasting time on internet typing long comments
@@Kottam_Yallawa if you aren't here to learn about tires, feel free to go look at pictures of cats and shut your brain off, since you obviously don't value it
@@CorvusCorone68 says the person who got offended by random internet comment 🙂
A contact patch gives more grip for a few reason. When you add weight to the rubber its grip does not go up in a 1 to 1 fashion. Rubber has a diminishing result when more weight is added exponential at first then tapers. So if you go over the max weight for a set contact patch and material your grip will stop increasing because the rubber will tear and deform. Also the rubber has a mechanical key with the road as it drives over much like you talked about in your video and the coefficient of friction doesnt equate for the keying on the road where the rubber can grab the road and has a mechanical bond at a microscopic level. The rubber also adheres to the road in a small way depending on compound. Since were talking about wider tires and race tracks I will also assume stickier tires. At a molecular level the tire adheres to the road surface slightly and more stickiness means more gripyness. As the rubber moves to the road surface that is robbing energy which means more grip by turning kinetic energy into heat.
18:11 💯 kinda like a PC can look good and also perform at the same time, tires can too 😍
When i worked at michelin we were actually taught some of this. It was a way of teaching us why each component of the tire was important
The normal force is a function of the area. When you consider the massive downforce cars experience larger tire allow for longer use, less wear, and sufficient traction. Going smaller with your tires may result in a greater normal force but you could experience mechanical failure on the very surface of the tire resulting in faster wear and reduced grip.
I felt like the dumbest smart guy or smartest dumb guy when you asked the grip question and automatically said "something about a coefficient" and I was not entirely wrong 😂
Coefficient of friction only takes into account the resistance to sliding of two materials with perfectly flat surfaces. Like you mentioned with tires conforming to the surface, a larger contact patch adds more peaks and valleys that can apply force in a horizontal direction. It may only be a fraction of a pound per little valley/groove, but the more you have, the more it adds up.
On top of that, you get into footprint mechanics where the slip angle of the tire isn't consistent through the length of the contact patch. If you make the contact patch longer instead of wider, you get a less optimized slip angle through the length of the contract patch. A wider tire adds the same area (for increased grip from the above behavior) but also keeps the slip angle through the contact patch more consistent/optimzed, resulting in higher grip. That's one of the reasons old, classic race cars on skinny tires always looked like they were drifting through corners.
Excellent video dude. Keep up the great work!
Keep that uniqueness up
6:42 damn I've never heard anyone do a combination Jar-Jar Binks/Shaggy (the singer) impression but I gotta say I love it
Lol
Lmao gottem
Love your guys content its what go me into cars to begin with and now I'm closer to my dad because of it.
So glad this dude is part of this channel
Te Best episode of B2B, thanks
I really like donut media they have helped me understand material covered in my automotive classes. This one is a bit late
Mu in the friction equation is a variable not a constant and surface area plays a huge role in determining the value of Mu
Right, to expand on this, each tire will have its own value for Mu. A wider tire will have a higher coefficient of friction when compared to a thinner tire that is made of the same material, has the same diameter, and is inflated to the same pressure. So wider drag tires will have a higher value for Mu, giving a greater frictional force overall for a vehicle of the same mass (since the Normal Force is just the mass of the vehicle multiplied by acceleration due to gravity). Inflation pressure and diameter will also play a role in changing the Mu value for a tire.
The classical model for the friction coefficient applies to grip in terms of the car's mass and speed but does not count for how the traction deals with angular momentum during turns or directional speed especially when factors like down force are applied. Wider tires help even out these changes to conserve momentum
I love Donut! I always learn something
Hey JerryBerry, you’re using the frictional force equation in terms of force. That is good for 1D projected models, but in reality what you want to consider as grip is PRESSURE. Pressure is force times an area, which will give you a numerical 2D referenced grip that you can then project onto the road surface for road contact.
edit: Physics and Civil Engineering Major 🤌🏽
You mean pressure is force DIVIDED by the area unless you mean force is equal to pressure TIMES area but yea, need a varying reference than a constant one
Edit: Mech Eng Major
@@jsrocker248 or you could just think about it in the simplest terms possible. He didn’t ask for it to be over complicated. Distributed load. If you have a force that stays the same (i won’t be using any eq this is just simple physics) and a small contact patch your pressure or F/in^2 will be high. Whereas if that contact patch is larger. You get a smaller F/in^2. Never passing out of the threshold of static friction at any single point.
I’m a lil on the weird side. Biological Engineering Major.
@@zexcthd5519 Dude, I totally missed that 😂 your right, you can just use dynamics by distributed loading of the tires area
@@jsrocker248 yeah. Everyone is going with very complicated answers that are right but we can’t just take it all the way back and explain this. Not to say their answers are wrong it’s just tires are so complicated. There’s so many answers. It’s mainly distribution of heat and load. Along with other things like the strength of the actual rubber to no shear off fast. It’s so complicated you can’t really straight forward give a specific answer.
This comment needs more attention so bump
I thought you will also tell about classic white tires and the history of white-walled tires. =)
Same I was disappointed when he passed through it in the beginning as if they never even existed 😢 but the low ridin chicanos still rock those on their classic old school low low riders....what's up esé, what set chu claim 😎
Less we forget.
He mentioned that carbon makes the tires stronger, UV resistant, and black. That's the whole story isn't it?
th-cam.com/video/_09XHdZhtSI/w-d-xo.html
They already made that video. Dig deeper
Very informative thanks donut 🍩
I've studied suspension design and grip theory of race cars in engineering school. If you double the weight on the same tire/suspension package, your grip does not double, it's slightly less. Same goes the other way, if you halve the weight, you have slightly more than half the grip. Friction coefficients are VERY general in the assumptions that go into them for general calculations. Realistically, the surface area statistically gives more peaks to grip, and if your compound is optimized for the weight and temperature, it will engage more of these peaks to increase mechanical grip.
Edit: Doubling the weight and not resulting in double the grip is due to shear forces exceeding the limits of the material itself at a microscopic level.
Answer to Uncle Jerry's question: I've wondered about this a long time. My guess is that the wider tire allows for more opportunities for the best possible coefficient of friction to exist between a given contact patch of tire and asphalt. The coefficient of friction is a point property, meaning that it changes to some degree at every point that it is measured. So more contact, better chance of a pebble or particularly bad surface to not ruin that coefficient. Although I'm sure there are a lot of other contributing factors
Jerry - The maximum friction between the tire and the pavement is determine by your equation Friction = mu * Fn, where Fn is determined by the weight of the car. However, when the drag car launches off the line, there is torque from the axel that rotates the wheel. This creates a new horizontal (tangential, not normal) force, and therefore a shear stress (Horizontal Force * contact area) between the tire and road. A higher area gives the tire more ability to translate the rotation of the wheel into forward motion of the car without having the tire break free due to exceeding that stress limit (i.e. burn out). Increasing contact area reduces the stress, and therefore area is very important. T-shirt?
You're right, the width of the tire is used while calculating the friction force created by the amount of torque
Like you said, myu is variable. Myu is also difference between sliding and rolling friction. To improve the average value of myu, a larger contact patch helps. Also To increase the friction force you need to increase the Normal force. Imagine the weight of a dragster on bicycle tyres with the same compound. While it may do the same job for the first few inches, the wear won’t survive the length of the drag strip.
My dad taught me about tires and suspension. This is a throwback for me!!
Answer:
Ff and Fn are perpendicular to each other. Fn is perpendicular to the surface while Ff is parallel to the surface. Unless you get into small dimensions where entrenching occurs, two (same material) objects of equal mass with different proportions will share the same frictional coefficient.
A tire with the same mass that is twice as tall and half the width of another tire while sharing equal mass will have the same frictional coefficient. (assuming everything else is equal)
It's easier to increase the mass of a tire by widening it rather than making it taller. When you increase the surface area, the pressure is spread out more due to them sharing an inverse relationship. So a lighter and wider tire would have less friction then a narrower heavier tire. (assuming everything else is equal).
All in all, surface area "doesn't matter". If you increase surface area you spread out the same amount of force over a wider area which balances out and has no change on the frictional coefficient. However if you increase the mass AND surface area, you can increase pressure between the tire and the surface giving you more 'grip'. Wider tires also have other benefits with relation to temperatures, etc.
*Note that those Racing Slicks are not just bigger, they're more massive (heavier) 😊
I'm not an engineer and I'm not 'smart'; I guarantee someone will provide a much better explanation with proper equations to support them. I don't currently know the shortcuts to type "Ff" and "Fn" properly lol. (But I'm trying to get a free shirt here Dammit!...)
***Edit*** smh... I'm reading other comments that are making me doubt myself here... there are other factors I didn't consider but will hold steadfast... I really want a damn shirt... and a sticker.......and some jungle nuggets......
Drag tires are extremely light weight.
In fact, they weigh about half the amount that a street tire of the same size would weigh.
Answer to question about friction and wide tires: The same force distributed over a wider patch allows the tire to better retain the shape, a narrow tire would deform easily under the same force - losing friction. Also, tire temperature is better managed over a greater area, the smaller patch would over heat much faster.
Isnt deformation of the rubber to the road surface what you want tho? Wouldnt having more load on a narrower tire increase its deformation and subsequent friction making more grip?
@@beachboardfan9544 I was gonna say he is clearly a master..... Look at his martial arts Gi. Looked closer and it's a collared shirt with a man purse......carry on
@@johndough5854 😁I'm not busting is his balls, my questions are sincere.
@@beachboardfan9544 I think they have solved what you speak of with the sidewall of the tire. Drag Slicks have a very soft sidewall that allows for the deformation you speak of..
@@beachboardfan9544 Higher deformation equals faster, deeper wear and tear! To increase tire life you’d have to increase the compound hardness, which negates the effect you desire.
You really can see that he enjoys making these. I love that
Maybe someone already said it, but it expands your contact patch. A larger circumference allows a larger ‘flat’ spot on the bottom. And a wider tire just makes the other dimension of the patch longer. It’s an increase in surface to surface friction over a given space.
Este es uno de los episodios más interesantes e informativos que he visto aquí en este canal, gracias Jeremías!!! 😎👍 (Mi hijo de 13 años y yo de 50 años, somos de Venezuela y vivimos en Orlando, FL y nos encantan tus videos)
Mi mejor amigo es de Venezuela, vive en Miami. Que curioso es el mundo! Saludos!
Jerry: tires are the only part of the car that touches the ground
Stance nation : I beg to differ
Yea fuck stance.....
That’s stance/camber gang not rice. Get your stereotypes right.
@@K20_EM1 Geez sorry
Hey Jeremiah! Please do a video explaining how the Bentley's W16 engines work. Love your show dood, Peace!
Yep i changed from Toyo proxies T1R v pattern to proxies TR1 asymmetric pattern. I changed a couple of months ago after 20 years using T1Rs. TR1s are better even though it messes with my car OCD👍👍
Mall crawlers endangering all of us with their high center of gravity making emergency turns suddenly dangerous. I'd love to see a moose test with a modified vs stock modern day 4wd suv or truck.
Moose Test doesn’t make sense to me… why can’t you brake AND turn?
I think it’s just a name for a stability at speed rating.
I'd love to see the hydroplaning tests with those too.
@@goawayihavecommentstomake1488 because braking and turning cause imbalance in the car's weight distribution. This can lead to understeer and/or higher chance to oversteer once you turn, and I don't think it is easier to manage than having the car balanced. This is why you should learn defensive driving.
@@goawayihavecommentstomake1488 Think about it like this, there's a car reversing out of a driveway right in front of you, do you hit the brake; Potentially slowing you down and increasing the amount of time you're behind this car? Or do you turn sharply to avoid a collision.
Coulomb's law of friction is only relevant when two perfectly flat surfaces meet. For example stiction isn't accounted for, as are many other real world changes. As noted, the ground isn't actually smooth in the case of road surfaces and rubber tires, and so Coulomb's law does not hold. In this case there are many factors to be noted. Bigger tires (at the same pressure) don't actually increase the size of the contact patch, with the same weight (pounds) and the same pressure (per square inch) the size (square inches) has to be the same. However by making the contact patch shorter and wider there is a number of benefits. The main being due to the rotation of the tire. Viewed from above the forwards motion of the tire is always changing. The leading and trailing edges are slower, whilst the middle is full speed. This means the leading and trailing edges are both being dragged along the ground slightly to bring them to the same speed, whilst the middle (with the most weight) is having to fight that. A shorter contact patch means less of that effect, whilst wider doesn't reduce grip in any way leading to a net benefit. This pulling also stretches the tires and heats them, whilst producing losses (one part of the reason higher pressures provide less drag).
Another factor to remember is that the grip of tires decreases as weight is increased. Or In Coulomb's law, the Mu decreases as weight increases (leading to a higher force overall, but tending to decrease in a curved way similar to a log x graph). This is due, in part, to micro tire deformation into the cracks. It takes little force to get a moderate amount of keying into the cracks and bumps producing grip (due to the asymmetric lateral forces on the bumps as the tire slips - tires MUST slip to produce grip). However as force is increased there is far less to gain squeezing into the final part of the gap, and this leads to less improvement. Reducing the pressure increases the size of the contact patch, and so the force pressing into the cracks is reduced and spread out leading to a net gain of grip. This is also why equal weight on all tires produces more grip than high body roll or high anti-roll bar settings.
There's a lot more which goes into it, but those are two of the most important factors as to why bigger tires and/or lower pressures helps with grip. Other fun tire examples, the asymetric grip of a contact patch through corners (outside half of the tire travels further than the inside half producing a twisting moment we see often as bikers lose grip under braking). As a motorbike rider rather than car driver there's a few motorbike specific fun things such as the changing contact patch as the bike leans producing many effects. But there are still fun effects for cars such as an upright car tire with a strong lateral force bending the rubber below the rim seen quite vividly in 50s F1 which produces the need for camber. Or the optimal tire yaw (ie sideslip angle) changing as the weight on wheel changes leading to race cars setting the outer tire to turn more tightly than the inner tire, or "anti-ackermann" to produce slightly more grip. Lots of interesting and cool effects go into tires once we get past the myth of Coulomb's law with respect to tires.
Hmm, I haven't heard of striction before but what you say does ”sound” realistic. The attention to detail is impressive and I happen to agree with it all including the last part about it being interesting and cool
How lonely, are you?
@@Kottam_Yallawa Not lonely, but educated. Likely an engineer or engineering student. Most of us know that basic information.
I had assumed people fit wider tires so they could use a soft compound for more grip but by having more of it be able to maximize the longevity of the tire and maybe spread out temperature more evenly throughout it for consistency from the larger thermal mass.
Where I live All Weather tires are the best you never have to change them till they wear out, theyre good enough in the snow and work well enough in the rain and summer, if youre in Southern California you only need one tire as well lol.
Short answer: To increase the _odds_ of optimal grip -More surface means more probability of contact points with maximum friction. It’s probabilistic.
Engineer/particle physicist here. The reason that surface area isn't accounted for in the equation for friction coefficients is based largely on the fact that epstein didn't kill himself followed by the numerical representation of pi which is roughly 3.14159
Bro straight did a JarJar impression while doing the Vulcan Salute from Star Trek and said Star Wars movie 🤣 Great video by the way! I love learning how things are composed and how they work
My guess is more rubber equals cooler temps. Better heat dispassion. Awesome video sir’s!!!