Need Motivation To Lean More?

[Kevin2109]

Originally Posted by dfox

It's the way my mind works, the way I view the world. I see things in concepts, not in definitions. My spatial reasoning is how I interact with the world. I see things in my head in four dimensions. I can visualize how the center of gravity shifts and how that changes the distribution of weight between the front and rear tires. I can visualize why counter steering works, instead of just having someone tell me it does and learning strictly from experience. I understand this is not the way the normal person views the world, and don't think that my way is better or worse, I just have a different skill set, which is why I am an engineer.

[Motofool]

Originally Posted by alex.s

ah yes, "cold tires". your post has me thinking... what other gases could be used outside of standard air (nitrogen/oxygen) and how would their viscosity effect the handling of the tire? how hard would it be to make a gas that is quicker to compress than it is to decompress? lol i wonder what air motogp tires run

I had friends using helium for some time.
Results: minimum weight and inertial momentum saving and increased rate of leaking out.

Opposite to liquids, the viscosity of gases increases with the temperature.

Gases act like springs: they store energy and release the same amount later; hence, I see very difficult that such a gas is achievable,.............but not impossible, I guess.

I don't know what GP tires use.

Here are a couple of schematics that show how the shape and size of the contact patch changes with lean angle for some tires, which was what started this discussion.

A couple of posts at the beginning of the thread (#3 and #12) pointed out the contact patch-lean angle dependance.

.

[Kevin2109]

Originally Posted by Motofool

I don't know what GP tires use.

Probably Nitrogen, If I had access to some all the time thats what I would be running. Its not effected by temperature and takes longer to leak out

[dfox]

Originally Posted by Kevin2109

Probably Nitrogen, If I had access to some all the time thats what I would be running. Its not effected by temperature and takes longer to leak out

The air in your tires is already roughly 75 to 80% nitrogen, enjoy it for free...

[alex.s]

Originally Posted by dfox

It's the way my mind works, the way I view the world. I see things in concepts, not in definitions. My spatial reasoning is how I interact with the world. I see things in my head in four dimensions. I can visualize how the center of gravity shifts and how that changes the distribution of weight between the front and rear tires. I can visualize why counter steering works, instead of just having someone tell me it does and learning strictly from experience. I understand this is not the way the normal person views the world, and don't think that my way is better or worse, I just have a different skill set, which is why I am an engineer.

yes. i am also an engineer. i also have an imagination. you are not unique in your "abilities"

however you have not answered my question. aside from a generic "level of grip related to forces applied to tire", there is no benefit in terms of kinetic ability or spacial reasoning to knowing how to accurately describe the forces applied on the tire.

lets take your countersteering example. i also try to visualize the exact effect and understand how it works. i understand that the countersteer pulls the front wheel one way causing a rotational moment, tilting the top of the bike away from the turn (into the intended direction). but at the exact same time, knowing that does absolutely nothing for me in terms of ability to operate the handle bars. regardless of knowing or being able to describe how counter-steering works, you push on the inside bar, you lean. you don't need to know the internal mechanisms to understand the relation between input and output. you of all people (an engineer, someone who prides them self on logically dissecting the functionality and construction of an object) should know that's the beautiful thing about neural networks.

[dfox]

Okay, this is just getting out of control. You obviously have some reason to keep arguing, and I do not. Understand that I enjoy knowing the physics behind what I do in life, and believe it increases my ability to understand the upper limit of my abilities.

[Motofool]

Did anybody go back to see edited post #1?

This may be the first Jiggle's thread that has branched off out of his brilliant control !!!

[Jiggles]

I don't care enough to argue physics

[Felipe the Ant]

You're all saying the same thing

[Felipe the Ant]

Originally Posted by dfox

Everyone talks about contact patch like its the end all.

Simple physics shows that until you lose traction, or are talking about melting rubber (think drag racing), contact patch means nothing.

and you're all missing the first part of his statement

[choneofakind]

Originally Posted by Jiggles

THIS IS A DISCUSSION THREAD ON CONTACT PATCHES, EVERYONE ELSE GTFO

Baaahahahahaha!

[Domagoj]

Originally Posted by dfox

Understand that I enjoy knowing the physics behind what I do in life, and believe it increases my ability to understand the upper limit of my abilities.

Your views remind me of my own at a time.

Yes, you are right, there was some confusion between terms grip and friction.

There is a very nice sentence that @Motofool has posted. It is the essence of what I tried to say before buy my clumsy english did not allow me to express myself accurately. I forgot to quote so I'll just paste it here:

"...rubber as a material is something between a solid and a very viscous liquid; it is compressible, so it digs deeper into the crevices of the pavement under higher normal force; its characteristics vary with temperature."

It is important because it emphasizes two very very significant factors.

First, being something between solid and viscous liquid, rubbers does not conform accurately to the friction formula for solid rigid bodies, which we discuss here.

Second, it changes state with temperature change. Cold rubber is completely different than a warmed up rubber.

Back to the formula.

Ff = coefficient * Fn

Elementary school math explains the relations between the two. It is clear to everyone that with CONSTANT coefficient, Ff (Force of friction) can be increased only by increasing Fn (normal force). Following this trail of thought leads to a simple solution that smaller contact patch leads to larger Fn and hence larger Ff.

What I'm saying here, is that coefficient is NOT CONSTANT, it is a function of temperature, contact area (contact patch) and other things. The question that I cannot answer is how exactly that function looks like.

Experience tells us that coefficient will increase as temperature increases, up to a certain level, then it will reach a maximum, and then keep dropping as tires overheat more and more. Typical example of this is too many laps with road tires on a track. Once your tires overheat you crash.

Experience also tells us that coefficient will increase as the contact patch increases, because there is a better chance with larger area that warm rubber will dig into the crevices of the road. This will also reach a maximum, and after it will keep declining because the normal force decreases and at a point becomes insufficient. Typical example is a light car with too wide tires, a common "tunning" mistake people like to make. The ground pressure becomes so small that the car actually looses grip.

Can you accept this as a plausible explanation for track tire behaviour?

Road tires also have a fluctuating coefficient, but much less so. They are much closer to a rigid body, formula becomes more accurate, and increase of contact patch does not bring benefit because the coefficient does not grow quickly enough in relation to the drop of normal force.

[Mountain Dew]

I'm starting to think the "d" in "dfox" stands for "douche."

[Fappy]

Originally Posted by choneofakind

So now back to tires. When you open the throttle during a turn, the torque applied to your wheel times the radius of the wheel is a force that propels the bike forward. But at a certain lean angle (or a big enough throttle opening), μmgcosθ (magnitude of friction due to normal force, unless I got the wrong trig function) will be less than the applied force on the back wheel, due to turning, and the wheel will spin or slide, even if the back of the bike squats and loads the back wheel.

So if we apply that same force from turning (same squatting rear, same throttle input, same lean angle) over a larger area on the same compound (but wider) tire, the pressure between the contact area and the idealized gym floor road would be less. Each unit area, dA, would have less force acting on it because the total friction force is split up over a larger area, so each individual dA would not be asked to deliver a force larger than μmgcosθ and the tire will not break loose. That's my logic.

I guess maybe I'm thinking grip (the probability that the tire will maintain traction - I liked your definition) and I'm using the word "friction"? I dunno, I just feel like they wouldn't use wider tires if they didn't have to; they impede how quickly the bike can lean over. But they also make identical tires in a 160 and a 180, so it's not just that a better compound is available in a wider tire.

My head is confused. It's nice outside. I don't have a ton of hw, and I already went to physics class today.

So essentially here, if you imagine a 60-foot wide tire, as opposed to a 5" wide tire, as long as they both have the same mass and material, the friction maintained by each tire would be exactly the same. Yes, you're exactly right that each unit area of floor/tire dA would have less force acting on it, and thus would be able to maintain grip for longer... IF there were also the same amount of normal force acting on each dA. But with that larger tire that weighs the same, the normal force on each unit area is proportionally less, such that the friction in the end is the same.

This actually brings up another benefit of using a wider tire in the real world, though. Aside from having a greater probability of reaching an area where grip is better, wider tires also usually have greater mass. Greater mass will hurt the bike's overall acceleration, BUT the tradeoff is that a heavier tire will be able to supply a greater frictional force to the rear of the bike because of the increased normal force acting on it.

Hope I cleared it up a bit?

[choneofakind]

Yeah that helped. I guess I just didn't take the normal force being proportionately less into account, which explained why I was confused.

Thanks for addressing my individual steps of thought.

[Fappy]

Originally Posted by Motofool

I had friends using helium for some time.

Here are a couple of schematics that show how the shape and size of the contact patch changes with lean angle for some tires, which was what started this discussion.

A couple of posts at the beginning of the thread (#3 and #12) pointed out the contact patch-lean angle dependance.

.

The tires are designed to maximize the contact patch, yes. But it's not for the reasons you might think. As was mentioned previously, maximizing the contact patch maximizes the probability that grip will be maintained over an irregular surface. It still does nothing to increase friction forces, but it DOES help to maintain so-called "grip".
See mah previous postzzs.

Friction != grip. These are separate things

[Asspire]

hmmm, I think jiggles tagged dfox's tires. Cause nobody on the internet argues about physics/math/science stuff for 3 pages, unless your on 4chan....

Where can I get a white marker for rubber?

[choneofakind]

Silver sharpie

[alex.s]

Originally Posted by Domagoj

Your views remind me of my own at a time.

Yes, you are right, there was some confusion between terms grip and friction.

There is a very nice sentence that @Motofool has posted. It is the essence of what I tried to say before buy my clumsy english did not allow me to express myself accurately. I forgot to quote so I'll just paste it here:

"...rubber as a material is something between a solid and a very viscous liquid; it is compressible, so it digs deeper into the crevices of the pavement under higher normal force; its characteristics vary with temperature."

It is important because it emphasizes two very very significant factors.

First, being something between solid and viscous liquid, rubbers does not conform accurately to the friction formula for solid rigid bodies, which we discuss here.

Second, it changes state with temperature change. Cold rubber is completely different than a warmed up rubber.

Back to the formula.

Ff = coefficient * Fn

Elementary school math explains the relations between the two. It is clear to everyone that with CONSTANT coefficient, Ff (Force of friction) can be increased only by increasing Fn (normal force). Following this trail of thought leads to a simple solution that smaller contact patch leads to larger Fn and hence larger Ff.

What I'm saying here, is that coefficient is NOT CONSTANT, it is a function of temperature, contact area (contact patch) and other things. The question that I cannot answer is how exactly that function looks like.

Experience tells us that coefficient will increase as temperature increases, up to a certain level, then it will reach a maximum, and then keep dropping as tires overheat more and more. Typical example of this is too many laps with road tires on a track. Once your tires overheat you crash.

Experience also tells us that coefficient will increase as the contact patch increases, because there is a better chance with larger area that warm rubber will dig into the crevices of the road. This will also reach a maximum, and after it will keep declining because the normal force decreases and at a point becomes insufficient. Typical example is a light car with too wide tires, a common "tunning" mistake people like to make. The ground pressure becomes so small that the car actually looses grip.

Can you accept this as a plausible explanation for track tire behaviour?

Road tires also have a fluctuating coefficient, but much less so. They are much closer to a rigid body, formula becomes more accurate, and increase of contact patch does not bring benefit because the coefficient does not grow quickly enough in relation to the drop of normal force.

and the cookie goes to... Domagoj!

[dino74]

Originally Posted by Jiggles

I don't care enough to argue physics

I'm with you

To me, its all the same difference...

[Dragonracer76]

Check out what the PO of my new ninjette left me... I can't wait until my new ones get here. Corners feel squirrely as hell with wannabe car tires..
2012-09-30 18.05.01.jpg
2012-09-30 18.05.29.jpg

[Jiggles]

Wow, how many miles on that bike?

[Dragonracer76]

10,000. I think he never got it over 50 or something. haha He was a bit older than me and just used it for commuting to work.

[Alex]

Seems like a kickstand is optional on that bike. Just stop and get off; it's not going anywhere.

[Dragonracer76]

Originally Posted by Alex

Seems like a kickstand is optional on that bike. Just stop and get off; it's not going anywhere.

Hahaha.. no doubt. like a built in center stand. You can see I've barely rolled over them on my way to school a couple of times. It'll be a much more fun trip once they're sorted.

The first 7 miles are twisty through the hills and woods, followed by a long run down a brand new 65mph highway, then into town.. coming home is better though. ...save the best for last..