Why do fat tires offer better grip on the road than thin tires? *SOLVED*

This is a good question and one which is commonly asked by students when friction is discussed. It is true that wider tires commonly have better traction. The main reason why this is so does not relate to contact patch, however, but to composition. Soft compound tires are required to be wider in order for the side-wall to support the weight of the car. softer tires have a larger coefficient of friction, therefore better traction. A narrow, soft tire would not be strong enough, nor would it last very long. Wear in a tire is related to contact patch. Harder compound tires wear much longer, and can be narrower. They do, however have a lower coefficient of friction, therefore less traction. Among tires of the same type and composition, here is no appreciable difference in 'traction' with different widths. Wider tires, assuming all other factors are equal, commonly have stiffer side-walls and experience less roll. This gives better cornering performance.

This guy doesn't know jack squat about tire compounds

 

[prvteye2003]

Originally posted by: Roger
It has more surface area, your analogy does not work with rolling traction Skoorb.

I would have thought this would have been obvious.

 

[StageLeft]

Originally posted by: Roger

This is a good question and one which is commonly asked by students when friction is discussed. It is true that wider tires commonly have better traction. The main reason why this is so does not relate to contact patch, however, but to composition. Soft compound tires are required to be wider in order for the side-wall to support the weight of the car. softer tires have a larger coefficient of friction, therefore better traction. A narrow, soft tire would not be strong enough, nor would it last very long. Wear in a tire is related to contact patch. Harder compound tires wear much longer, and can be narrower. They do, however have a lower coefficient of friction, therefore less traction. Among tires of the same type and composition, here is no appreciable difference in 'traction' with different widths. Wider tires, assuming all other factors are equal, commonly have stiffer side-walls and experience less roll. This gives better cornering performance.

This guy doesn't know jack squat about tire compounds

I prefer his answer to the second one though

 

[StageLeft]

Originally posted by: prvteye2003

Originally posted by: Roger
It has more surface area, your analogy does not work with rolling traction Skoorb.

I would have thought this would have been obvious.

Please state why. Apparently this is something most of us do NOT understand, whether we think we do or not

 

[SagaLore]

Originally posted by: Roger

It's true! The force required to move something when it's not moving is: f = uF where f is force required, u is the coefficient of friction, F is the normal force (force of gravity pulling it down). The equation is the same for a moving object except in that case f is the force required to keep the object in motion, and when something is moving u (kinetic friction now) is likely to be lower than static friction.

Fine Skoorb, equate this ;

4,000 lb vehicle

Use your equation to figure out the coefeciant of friction with :

2 inch wide tire

4 inch wide tire

6 inch wide tire

Show me that they all come out with the same friction.

Scoorb I think you just got your answer. Comparing it to the brick, let's say you put that brick on it's end but then attach an object of the same surface area and friction on the end and try to push that. That will give a different value than without the extra attachment.

 

[StageLeft]

Scoorb I think you just got your answer. Comparing it to the brick, let's say you put that brick on it's end but then attach an object of the same surface area and friction on the end and try to push that. That will give a different value than without the extra attachment.

But if you put the same weight on the brick when the brick is on it's side it's going to require exactly again the same amount of force to move it.

 

[Viper GTS]

Originally posted by: Skoorb

Originally posted by: prvteye2003

Originally posted by: Roger
It has more surface area, your analogy does not work with rolling traction Skoorb.

I would have thought this would have been obvious.

Please state why. Apparently this is something most of us do NOT understand, whether we think we do or not

Up until the moment the tire begins to spin it's a relatively simple friction problem. That is, of course, IF we assume that the force is applied horizontally to the ground (tangent to the rotation, which it is) and ignore tire deformation, thermal changes due to the force applied, & a myriad of other factors that could influence it.

The reality is that the extremely simplified equation used to evaluate friction in low level physics class has little to no application to a non-controlled, non-contrived environment.

Viper GTS

 

[radioouman]

Skoorb:

I honestly don't know which would be better on a dry surface. However, I can give you a little info on other surfaces. If it is wet or there is snow on the ground, then a narrower tire will give you better performance. A wider tire spreads out the force of the car, and you tend to ride on top of the water/snow; just like snow shoes. A narrow tire allows you to sink down to the pavement, so you don't hydroplane as easily, and you sort of push the snow out of the way.

 

[freebee]

Now another interesting question for you tire people....why do race cars (Nascar in particular) have such high profile tires?

I've heard debates on heat dissipation, load carrying ability, etc....and yet most road going GT cars (and most sports cars) have low profile tires (and are fairly heavy also). Yet notice even on F1 cars, their tires are these huge, high profile, donut type things.

 

[Regs]

Because the greater the surface area the more it reduces mechanical stress on the tires which increases their usability.

 

[StageLeft]

The reality is that the extremely simplified equation used to evaluate friction in low level physics class has little to no application to a non-controlled, non-contrived environment.

Well the equation is perfectly fine. What's wrong is the assumption that the coefficient of friction will divide equally as you expand the surface area. In a simple closed environment it will shrink perfectly equal in size to the expansion of contact. This way the coefficient when multiplied against the normal force will result in a consistent force required to move an object.

But the real question is why is the coefficient of static friction not inversely correlational with the increase in tire surface area? Both of the people in that website had answers which may in part be right.

One can note that since both of these people - who are physics teachers - had differing answers on the question, so the solution is not as simple as one might think.

 

[Regs]

Regards, Steve
Steven T. McCaw, Ph.D
Professor, Biomechanics
Graduate Program Coordinator
School of Kinesiology and Recreation
Illinois State University
Normal, IL 61790-5120

States:
Steve:

"I'm glad you found the site useful. Feel free to provide links to any of the lessons in the site.

The traction in tires is different than the standard force of friction that most physics textbooks talk about. In automobile tires, the edges of the treads are a major factor in preventing sliding. They account for much more traction or friction than the coefficient of friction of the rubber on the pavement. Of course, a wider tire would usually have more treads than a thin tire.

With racing tires, there are no treads. They try to get the tires hot, so the rubber becomes somewhat sticky. Also, the tire pressure is lower, so there is more surface area on the track. The traction from the stickiness of the rubber is proportional to the area on the ground."

 

[Parrotheader]

Just pay the extra $50 bucks for the wider tires you tighta$$.

 

the angle of the dangle is directly proportional to the heat of the meat!

 

Skoorb;
If I ever have the chance to meet you in person, remind me to sucker punch you in the face, you made my brain hurt and question my own beliefs.

 

Originally posted by: freebee
Now another interesting question for you tire people....why do race cars (Nascar in particular) have such high profile tires?

I've heard debates on heat dissipation, load carrying ability, etc....and yet most road going GT cars (and most sports cars) have low profile tires (and are fairly heavy also). Yet notice even on F1 cars, their tires are these huge, high profile, donut type things.

For handling
the sidewalls can flex, absorbing the syntrifical force

 

[StageLeft]

The traction in tires is different than the standard force of friction that most physics textbooks talk about. In automobile tires, the edges of the treads are a major factor in preventing sliding. They account for much more traction or friction than the coefficient of friction of the rubber on the pavement. Of course, a wider tire would usually have more treads than a thin tire.

That's feasible because the bumps in the tire kind of lock into the imperfections in the road.

Still not applicable to a drag car with slick tires though, unless it alludes loosely to the second answer by the physics teacher in the link above.

Of course in drag situations they do pre-heat the tires for stickyness..

 

[radioouman]

Originally posted by: Roger
Skoorb;
If I ever have the chance to meet you in person, remind me to sucker punch you in the face, you made my brain hurt and question my own beliefs.

 

[StageLeft]

Originally posted by: Roger
Skoorb;
If I ever have the chance to meet you in person, remind me to sucker punch you in the face, you made my brain hurt and question my own beliefs.

Sorry

 

[StageLeft]

Originally posted by: jntdesign

Originally posted by: freebee
Now another interesting question for you tire people....why do race cars (Nascar in particular) have such high profile tires?

I've heard debates on heat dissipation, load carrying ability, etc....and yet most road going GT cars (and most sports cars) have low profile tires (and are fairly heavy also). Yet notice even on F1 cars, their tires are these huge, high profile, donut type things.

For handling
the sidewalls can flex, absorbing the syntrifical force

While I'm at it I'll have you know that centrifugal force is a myth and does not in fact exist.

 

I can't even spell it, i'm not gonna argue about it

 

[MrColin]

Wrong, you will not get increased traction because the tire is smaller in width, why ?

In the snow you will have very poor traction on wider tires btw, compared to narrower ones. on asphalt however wider tires (all other things constant )will give better traction in that the wider tire has increased opportunity for friction in imperfect conditions, particularly with sideways movement.

 

[StageLeft]

Originally posted by: MrColin

Wrong, you will not get increased traction because the tire is smaller in width, why ?

In the snow you will have very poor traction on wider tires btw, compared to narrower ones. on asphalt however wider tires (all other things constant )will give better traction in that the wider tire has increased opportunity for friction in imperfect conditions, particularly with sideways movement.

OK mr. smartie pants - why do wheels seem to spin backwards on cars when you look at them?

:evil:

 

[Hayabusa Rider]

I'll have a crack at it. People are confusing traction with friction.

Lets do a thought experiment.

Lets say you are not working with a tire, but a cog gear on a car, like an old cog railway. Now lets suppose we apply power to this cog until it fails. Would it make a difference if the wheel (cog) was 1/10th of an inch wide or 6 inches? Yes it would. the wider gear is stronger. It can take more force before it shears. Now what if we made the teeth finer? The same principle applies. I submit that in the real world, tires and asphalt work the same way. Having wider tires (and a lower pressure), causes a larger contact patch, where more microscopic "teeth" and "grooves" can lock in, like the cog in the example. that tire can grip better because of it.

 

Originally posted by: Skoorb

Originally posted by: MrColin

Wrong, you will not get increased traction because the tire is smaller in width, why ?

In the snow you will have very poor traction on wider tires btw, compared to narrower ones. on asphalt however wider tires (all other things constant )will give better traction in that the wider tire has increased opportunity for friction in imperfect conditions, particularly with sideways movement.

OK mr. smartie pants - why do wheels seem to spin backwards on cars when you look at them?

:evil:

I thought they only "spun backwards" in movies...and I thought it was due to the capture rate of film