ESE's works engine tuner

**andreas** · 25th August 2022, 00:17

What do the slipper pistons say about things? And tires are not regarded as solid matter here either.
I don't know, therefore the question. Of course there is no concern for longegivety or cases where the material isn't within it's structural limits.

[QUOTE]
As an engineer, I know that friction does not depend upon surface area. As a car nut, I know that wider tires have better traction. How do you explain this contradiction?
Asked by: Mark Secunda

Answer
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.
Answered by: Daryl Garner, M.S., Physics teacher MacArthur High School, Lawton, OK

Friction is proportional to the normal force of the asphalt acting upon the car tires. This force is simply equal to the weight which is distributed to each tire when the car is on level ground. Force can be stated as Pressure X Area. For a wide tire, the area is large but the force per unit area is small and vice versa. The force of friction is therefore the same whether the tire is wide or not. However, asphalt is not a uniform surface. Even with steamrollers to flatten the asphalt, the surface is still somewhat irregular, especially over the with of a tire. Drag racers can therefore increase the probability or likelihood of making contact with the road by using a wider tire. In addition a secondary benefit is that the wider tire increased the support base and makes it hard to turn the car over in a turn or in a mishap.
Answered by: Stephen Scholla, B.A., Physics Teacher, Vienna, Virginia[QUOTE]

Including these quotes just to show some different opinion.

**Peljhan** · 25th August 2022, 01:59

Originally Posted by andreas

What do the slipper pistons say about things? And tires are not regarded as solid matter here either.
I don't know, therefore the question. Of course there is no concern for longegivety or cases where the material isn't within it's structural limits.

Including these quotes just to show some different opinion.

I asked myself this question right when we learned in high school about friction but physics teacher didn't know the answer.
Researched and made an explanation to myself few years ago when I was at university and had a debate with friend.
I came to conclusion that you can't apply basic friction rules to tires as friction surface is not relatively smooth.

If you look tires and asphalt contact you get small teeth that bind or interlock with eachother.
Imagine having a gear rack made of steel fixed on a table. You put another rubber gear rack on steel rack so they interlock teeth with eachother. If you use longer racks with more teeth (same teeth size), you will need more horizontal force to skip teeth.

This phenomenon is called mechanical adhesion.

**andreas** · 25th August 2022, 02:37

It's complex, There is the interlocking you mention, but the number and depth of those "teeth" must depend on the pressure, which will decrease as the tire gets bigger-very similar to basic fricton law. Similar but maybe The shear -friction can explain it more precise, we'll see.

**Frits Overmars** · 25th August 2022, 02:58

Originally Posted by husaberg

Frits can fix what i have wrong.

Yeah right. Your confidence is heartwarming Husa, but I don't even know if I should write tires or tyres.

**Vannik** · 25th August 2022, 06:04

On tyres:

The grip coefficient is made up of three components:

1. Friction coefficient
2. Interlocking coefficient - the soft rubber hooking on the surface roughness
3. Adhesion - between the rubber and the surface

2 and 3 increases quite dramatically with increase in tyre temperature.

**andreas** · 25th August 2022, 08:11

Originally Posted by Vannik

On tyres:

The grip coefficient is made up of three components:

1. Friction coefficient
2. Interlocking coefficient - the soft rubber hooking on the surface roughness
3. Adhesion - between the rubber and the surface

2 and 3 increases quite dramatically with increase in tyre temperature.

It's fair to read this as that contact patch-area is more like a secondary factor?

**JanBros** · 25th August 2022, 08:15

Originally Posted by Vannik

On tyres:

The grip coefficient is made up of three components:

1. Friction coefficient
2. Interlocking coefficient - the soft rubber hooking on the surface roughness
3. Adhesion - between the rubber and the surface

2 and 3 increases quite dramatically with increase in tyre temperature.

fuck temperature, we want to know about surface area

**wobbly** · 25th August 2022, 13:38

IMHO , yes we have the 3 factors as described by Neels.
But in the scenario of a tyre on asphalt we do not have the mass of a smooth block - sliding down a smooth plane on an angle , generating a prescribed Coefficient of Friction, as we all saw in Physics 101.
This is a specific context ( and the only one ) where contact area is classically deemed irrelevant.

But with one element having the highly deflective " sticky " characteristics of " rubber " and the other being an entire surface of solid peaks and valleys , any downward force on the rubber increases the mechanical adhesion
between these two very dissimilar surfaces.
Increase the area of interlocking adhesion ( contact patch area ) and the number of adhering points of mechanical contact increases.
Thus increasing the mechanical grip level.

This gives rise to the concept of the traction circle , wherein a downward force acts on an area of rubber in contact with the asphalt , and this generates an available level of grip that is a finite metric.
Increase the traction used in the direction of travel ( braking or accelerating ) then the level of traction available perpendicular to this ( sideways cornering ability ) is reduced , and visa versa.

Proof of this lies in the fact that a softer rubber in the contact patch area , will be torn off the underlying carcass , and be left behind on the asphalt faster than a harder version.
This torn off rubber adheres to the asphalt to such an extent that in Moto GP , and even more so in karting , there is , in certain parts of the track no asphalt to be seen.

Then we have sticky rubber adhering to even more sticky rubber , the result being high sides in MotoGP , and karts tipping up on the two outside tyres, due to so much mechanical grip between the surfaces.
Thus a wider tyre , or a softer tyre , does increase the Coefficient of Friction ( grip ) , between the two surfaces - as neither are smooth by the classic definition used in Physics 101.

**husaberg** · 25th August 2022, 17:13

Originally Posted by Frits Overmars

Yeah right. Your confidence is heartwarming Husa, but I don't even know if I should write tires or tyres.

i did see that but i am having mouse issues it has a mind of its own anyone know why my curser and highlight function is acting odd.

**HenkS** · 25th August 2022, 19:29

Originally Posted by peewee

hey guys im trying to make a paper template of the exh roof then cut it out to mark the bore for grinding but its looking more arched than i thought. i used what frits posted. 75% bore is center radius. maybe i bungled it somehow. but see the photo to be sure.
the other thing im trying to figure out is if you lengthen the exh passage how will the pipe react . original the passage length is 85% of bore. now its 171%. do you think the pipe might need to be significantly shorter or it wont matter much ? engmod could probly tell me but im not that good with using it

What about those 75%, I did not read any reply on that.
75% can't be good !

**andreas** · 25th August 2022, 20:37

Originally Posted by wobbly

IMHO , yes we have the 3 factors as described by Neels.
But in the scenario of a tyre on asphalt we do not have the mass of a smooth block - sliding down a smooth plane on an angle , generating a prescribed Coefficient of Friction, as we all saw in Physics 101.
This is a specific context ( and the only one ) where contact area is classically deemed irrelevant.

But with one element having the highly deflective " sticky " characteristics of " rubber " and the other being an entire surface of solid peaks and valleys , any downward force on the rubber increases the mechanical adhesion
between these two very dissimilar surfaces.
Increase the area of interlocking adhesion ( contact patch area ) and the number of adhering points of mechanical contact increases.
Thus increasing the mechanical grip level.

This gives rise to the concept of the traction circle , wherein a downward force acts on an area of rubber in contact with the asphalt , and this generates an available level of grip that is a finite metric.
Increase the traction used in the direction of travel ( braking or accelerating ) then the level of traction available perpendicular to this ( sideways cornering ability ) is reduced , and visa versa.

Proof of this lies in the fact that a softer rubber in the contact patch area , will be torn off the underlying carcass , and be left behind on the asphalt faster than a harder version.
This torn off rubber adheres to the asphalt to such an extent that in Moto GP , and even more so in karting , there is , in certain parts of the track no asphalt to be seen.

Then we have sticky rubber adhering to even more sticky rubber , the result being high sides in MotoGP , and karts tipping up on the two outside tyres, due to so much mechanical grip between the surfaces.
Thus a wider tyre , or a softer tyre , does increase the Coefficient of Friction ( grip ) , between the two surfaces - as neither are smooth by the classic definition used in Physics 101.

Thanks Wobbly, for the extensive answer. Do you also have an appreciation of how large the adhesion part of the total grip may be?

**husaberg** · 25th August 2022, 20:55

uncle kevin
https://www.cycleworld.com/2013/12/2...increase-grip/

Contact patch diagramOf the two contact patches above (left and middle image), which has the most grip? The one in the middle, with more rubber touching the road. At right, the contact patch of a bike at a healthy lean

QUESTION: I believe you’ve gotten the physics incorrect in your “Control the Contact Patch” sidebar (“The Pace 2.0” by Nick Ienatsch). A bigger contact patch does not give a tire more resistance to sliding: The force of friction is proportional to the normal force (F=mu x N), where F is along the surface and N is perpendicular to it, and mu is the coefficient of (static) friction.

The force of friction parallel to the road surface (“grip”) is equal to the coefficient of static friction times the normal force, which is the weight on the tire. If the size of the contact patch alone caused greater friction, then putting a wider tire on a motorcycle would automatically give more grip. It doesn’t.

Owen Hayes
Philadelphia, Pennsylvania

ANSWER: Amonton’s Law for physics describes the behavior of many elastic solids. Friction is directly proportional to the area of actual contact between the two solids, which is normally only a small percentage (like five percent) of the apparent area of contact.

If the solids have linear elasticity, then doubling the force pressing the two surfaces together will double the area of actual contact, and that, in turn, will double the frictional force required to slide one across the other. Linear elasticity is essentially the same as saying the material has a constant, rather than progressive spring rate.

Rubber does not display linear elasticity. Instead, it has a “rising spring rate.” An applied light load pushes a lot of rubber into actual contact. When that load is doubled, you do not get doubled area of actual contact because the rubber is stiffening. A better strategy, therefore, is to double the area of apparent contact. With tires, this is the footprint area. This is why the tires of racing cars are so extremely wide.

Nick writes about what goes on as the rider transitions from braking to throttle in mid-corner and the importance of maintaining the size of the footprint by never allowing the tire to significantly unload. Being the weird material it is, rubber sliding on an uncontaminated glass surface can produce friction as high as 10 times the applied load. If this could be achieved on highway or racetrack, riders would be dragging their faceshields.

plus some car thing i found that makes sense