The Surprising Science Behind Tread Patterns

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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[dannyallyn]

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 <3 keep up the good work

[kyleohara]

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.

[JulienAzelart]

this episode is giving me some science garage vibes lol (still miss that show 🥲)

[twostrokeproductions]

“The only part of the car that touches the road”
My lowered shitbox: *Frame proceeds to hug the ground*

[benfishburn]

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?

[thedrunkgamer]

I love this episode, it brings me back to science garage with Bart. "Don't tell my wife." Lol

[rileysmith]

I can't wait to watch this in college as apart of my course

[paperboy]

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.

[mmatthews]

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.

[legovirgo]

If Jeremiah taught a high school science class, those kids would learn so much!
At the same time, allowing Jeremiah to influence young minds..

[Jake-nmps]

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

[HartyBiker]

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.

[wesandbutters]

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.

[TampaBayRaysRocks]

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!

[jackdunn]

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!

[geeky]

I laughed really hard seeing the Subaru hit that pole in the snow when talking about grip coefficient and water. Just perfect

[codyjayne]

when Nolan is just drilling at the table during the "Mo Powa Babeh" Ad. LMFAO

[Drhofman]

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)

[stevengager]

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.

[tjrivera]

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