Fat tires work better not because of increased friction

[yhelothar]

My physics professor claims that surface area has nothing to do with friction.
So then what makes fat tires more effective?

 

[glen]

Originally posted by: virtualgames0
My physics professor claims that surface area has nothing to do with friction.
So then what makes fat tires more effective?

surface area has never mattered in the friction equation - it is factored out when calculating presure.

 

[yhelothar]

nevermind..
I googled it after I made the post
http://www.madsci.org/posts/archives/oct98/908313145.Ph.r.html

 

[yhelothar]

Originally posted by: glen

Originally posted by: virtualgames0
My physics professor claims that surface area has nothing to do with friction.
So then what makes fat tires more effective?

surface area has never mattered in the friction equation - it is factored out when calculating presure.

If you factor pressure.. skinny tires would actually be more effective as less surface area would equate to more pressure.

 

[glen]

Originally posted by: virtualgames0

Originally posted by: glen

Originally posted by: virtualgames0
My physics professor claims that surface area has nothing to do with friction.
So then what makes fat tires more effective?

surface area has never mattered in the friction equation - it is factored out when calculating presure.

If you factor pressure.. skinny tires would actually be more effective as less surface area would equate to more pressure.

Nope - more pressure per area
The presure is the same.

 

[glen]

p=F/A

 

[radioouman]

Roads are imperfect. Get a piece of gravel under your skinny tire, and you are likely to lose traction. Get a piece of gravel under your fat tire, and you may not notice.

Fat tires help in cornering because they are wider and resist the force to roll under better. (of course, the stiffness of the sidewall has something to do with this too.)

 

[yhelothar]

Originally posted by: glen

Originally posted by: virtualgames0

Originally posted by: glen

Originally posted by: virtualgames0
My physics professor claims that surface area has nothing to do with friction.
So then what makes fat tires more effective?

surface area has never mattered in the friction equation - it is factored out when calculating presure.

If you factor pressure.. skinny tires would actually be more effective as less surface area would equate to more pressure.

Nope - more pressure per area
The presure is the same.

By your equation, F/1 would give a larger pressure than F/2.
Thus tires twice as fat would have exactly half the pressure. A perfectly inverse relationship.

 

[fuzzybabybunny]

Wait, what?

"As your driver accelerated through the turn the skinny tires deformed excessively
and therefore were not able to remain in contact with the surface. If you
had chosen the wider tires, however, the tire would of deformed less under
pressure because of its greater stiffness..."

Errr... the skinnier tire deforms more and this act of deforming decreases the surface area of the tire in contact with the road.
The wider tire deforms less and this in turn means more of the tire's surface area stays on the road.
To say that a wider tire grips better than a skinnier tire simply because it deforms less is an interesting way of thinking...

Mathematically, yeah, surface area probably factors out. It's like saying OMGBBQ is not included in this formula: X/OMGBBQ * OMGBBW/2 = X/2

 

[glen]

Originally posted by: virtualgames0

is the same.

By your equation, F/1 would give a larger pressure than F/2.
Thus tires twice as fat would have exactly half the pressure. A perfectly inverse relationship.
[/quote]

Ff = µN,
N= the normal force
N does nto change with area
therefore, Ff does not change with area

 

[yhelothar]

Originally posted by: glen

Originally posted by: virtualgames0

is the same.

By your equation, F/1 would give a larger pressure than F/2.
Thus tires twice as fat would have exactly half the pressure. A perfectly inverse relationship.

Ff = µN,
N= the normal force
N does nto change with area
therefore, Ff does not change with area

[/quote]

Why are you going back to the original friction question when we're talking about pressure?

Also, you don't prove much when you can only explain things through equations as opposed to explaining them conceptually. It shows a lack of understanding too. It's like you just memorized the equations without fully grasping the concepts. Anyone can memorize equations.

 

[mercanucaribe]

Wtf is all that malarky about skinny tires deforming more? That's pure bullsh!t, probably made up by some high school physics teacher. If it were about deformation, skinny low profile tires would grip just as well as wide ones. Or how about just overinflating the tires for stiffness, while reducing contact patch to 1/2?

Imagine climbing up a rock face with two hands. Now imagine climbing up with eight hands. Which do you have better "traction" with? The tire-road contact isn't a contact between two hard surfaces, but between a bumpy surface and a soft material that conforms over it. The more rubber conforming over bumps in the road, the better the grip.

 

[glen]

Originally posted by: virtualgames0
Why are you going back to the original friction question when we're talking about pressure?

Also, you don't prove much when you can only explain things through equations as opposed to explaining them conceptually. It shows a lack of understanding too. It's like you just memorized the equations without fully grasping the concepts. Anyone can memorize equations.

The normal force is the weight of the car.
This does not change - no matter how wide the tires on the car are.

The weight of the car is the mass of the car multiplied by the gravitational force of the plant you are on.

 

[yhelothar]

Originally posted by: glen

Originally posted by: virtualgames0
Why are you going back to the original friction question when we're talking about pressure?

Also, you don't prove much when you can only explain things through equations as opposed to explaining them conceptually. It shows a lack of understanding too. It's like you just memorized the equations without fully grasping the concepts. Anyone can memorize equations.

The normal force is the weight of the car.
This does not change - no matter how wide the tires on the car are.

The weight of the car is the mass of the car multiplied by the gravitational force of the plant you are on.

Ok now you're just making random strawman arguments.
It's quite obvious by looking at the equations that surface area does not come into play, you don't need to state that.
However, the question wasn't about how surface area isn't in the equations, but it's about what makes fatter tires better if it's not friction.
Again, you've brought no concepts to the table but your elementary equations.
You were wrong on the pressure thing, so now you're trying to change subjects by talking about random elementary things. Stop wasting my time.

 

[yhelothar]

Originally posted by: mercanucaribe
Wtf is all that malarky about skinny tires deforming more? That's pure bullsh!t, probably made up by some high school physics teacher. If it were about deformation, skinny low profile tires would grip just as well as wide ones. Or how about just overinflating the tires for stiffness, while reducing contact patch to 1/2?

Imagine climbing up a rock face with two hands. Now imagine climbing up with eight hands. Which do you have better "traction" with? The tire-road contact isn't a contact between two hard surfaces, but between a bumpy surface and a soft material that conforms over it.

Your climbing up a rock analogy doesn't seem to work as both would have equal traction considering there is no slippage. 8 hands would be more ideal as there is more power. If you gave each of the 8 hands a quarter of the power compared to the 2 handed guy, they'd both go up the same rate.

 

[CombatChuk]

With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

 

[Toastedlightly]

Anyone figure that the wider tires usually have a softer compound therefore granting more friction?

 

[ArchCenturion]

Are we talking pound mass or pound force?

 

[Vic]

Originally posted by: CombatChuk
With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

This is correct. The area of the contact patch is determined by the air pressure in the tire, the hardness of the rubber compound, and the weight of the vehicle.
Tire size, skinny or fat, determines the shape of the contact patch, not the area. It is the wider shape of the contact patch that makes fatter tires more effective in cornering. Note that dragsters have skinny tires, those are more effective for straight-line acceleration.

 

[Toastedlightly]

ever think it may have to do with force applied per square inch? For instance, in a corner, the force is more spread out (but still the same)

 

[yhelothar]

Originally posted by: Vic

Originally posted by: CombatChuk
With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

This is correct. The area of the contact patch is determined by the air pressure in the tire, the hardness of the rubber compound, and the weight of the vehicle.
Tire size, skinny or fat, determines the shape of the contact patch, not the area. It is the wider shape of the contact patch that makes fatter tires more effective in cornering. Note that dragsters have skinny tires, those are more effective for straight-line acceleration.

It still seems like the tire width would serve as a coefficient for the contact patch.
Say 20psi gives allows 1cm of tire to make contact with the road. If the tire is 10cm wide, it would have an area of 10cm². If the tire was twice as wide, 20cm, it would have an area of 20cm².

 

[mercanucaribe]

Originally posted by: Vic

Originally posted by: CombatChuk
With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

This is correct. The area of the contact patch is determined by the air pressure in the tire, the hardness of the rubber compound, and the weight of the vehicle.
Tire size, skinny or fat, determines the shape of the contact patch, not the area. It is the wider shape of the contact patch that makes fatter tires more effective in cornering. Note that dragsters have skinny tires, those are more effective for straight-line acceleration.

Have you ever SEEN a dragster? They have skinny FRONT TIRES and fat REAR TIRES. The REAR tires are the ones providing the propulsion and the front tires are just holding the front up-- they are narrow to minimize air and rolling resistance. Aren't you the guy who is always trumpeting his car knowledge?

 

[LordMorpheus]

Your highschool phyics book says that contact area doesn't matter. If you were to continue your studies you would discover that this is not all that true. Columb friction is just the product of normal force and the coefficient of friction for the two surfaces, true, but when you've got a tire on the ground there are approximately 50 billion more things that need to be considered and it turns out that bigger contact patches give you more grip before they start sliding.

 

[smack Down]

Originally posted by: Vic

Originally posted by: CombatChuk
With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

This is correct. The area of the contact patch is determined by the air pressure in the tire, the hardness of the rubber compound, and the weight of the vehicle.
Tire size, skinny or fat, determines the shape of the contact patch, not the area. It is the wider shape of the contact patch that makes fatter tires more effective in cornering. Note that dragsters have skinny tires, those are more effective for straight-line acceleration.

Umm you are complete wrong if you think the width of a tire has no effect on the size of the contact.

 

[Vic]

Originally posted by: mercanucaribe

Originally posted by: Vic

Originally posted by: CombatChuk
With wider tires you don't get a bigger contact patch, you change the shape. Wider tires will have a contact patch that wider itself but the area will stay the same

This is correct. The area of the contact patch is determined by the air pressure in the tire, the hardness of the rubber compound, and the weight of the vehicle.
Tire size, skinny or fat, determines the shape of the contact patch, not the area. It is the wider shape of the contact patch that makes fatter tires more effective in cornering. Note that dragsters have skinny tires, those are more effective for straight-line acceleration.

Have you ever SEEN a dragster? They have skinny FRONT TIRES and fat REAR TIRES. The REAR tires are the ones providing the propulsion and the front tires are just holding the front up-- they are narrow to minimize air and rolling resistance. Aren't you the guy who is always trumpeting his car knowledge?

:roll:

You ever watch what happens to those "fat" rear tires when the green light goes on and the torque hits the pavement?