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jdugen said:
Ha! Its my turn now! Newtons Law, ( a good Salford lad). Every action has an equal and opposite reaction, cant f*ck with the basic laws of physics, no matter how much you puff your chest out. You are feeding a force into a structure, this force is operating around the central contact patch of the tyre. You are feeding this force at a point to the right (late) or the left (early models) of the GPZ / EX. Like it or not, that structure will attempt to twist around this central fulcrum. Unless you know more than Mr. Newton?
chest puffing? Classy, i can see you just want to be argumentative and just dont know what your talking about. Sounds good to me.

Newton actually has three laws that we commonly reference. Your speaking of the third which is actually "The mutual forces of action and reaction between two bodies are equal, opposite and collinear."

So we can apply this to the brake pads, and an equal force would be pushing on them from the rotor.

Ill go ahead and define collinear just so theres no confusion.

A set of points is collinear if they lie on a single straight line or a projective line.

So first I would like to point out that you have backed up your statement with something that you clearly do not understand very well because it does not apply to your explanation.

Secondly I would like to question what the twisting is you are talking about. Again, you clearly just dont understand physics. The caliper on your bike works by using a piston to push 2 brake pads together. These two brake pads sandwich a rotor. Mr Newtons third law, which you were so eager to point out and then completely ignore, tells us that there will be an equal force exerted on both sides of the rotor as well as the surface of each pad. These forces are equal according to mr newton and yet you seem to think that somehow an unequal twisting force is then applied. Your problem is you do not understand WHERE the forces are being applied. They are not applied to your forks. They are applied to your rotors and pads.


But but but the caliper is attached to the fork. Indeed it is. However because both sides of the pads apply equal forces to the rotor the system is contained inside of the caliper. The caliper centers itself over the rotor.

Went to school for engineering btw...
 

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since we are talking engineering (went there too), and since this discussion is getting a bit theoretical, maybe someone can explain to me the whole 'wider' tire and bigger contact patch idea for better friction. The force of friction is the coefficient of friction multiplied by the Normal Force. Nowhere does the surface area come into play. I have puzzled with this for a while, and have asked a couple of profs, but never got a good answer.
 
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luco.vico said:
since we are talking engineering (went there too), and since this discussion is getting a bit theoretical, maybe someone can explain to me the whole 'wider' tire and bigger contact patch idea for better friction. The force of friction is the coefficient of friction multiplied by the Normal Force. Nowhere does the surface area come into play. I have puzzled with this for a while, and have asked a couple of profs, but never got a good answer.
Coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large rubber patch has the same coefficient of friction as a small rubber patch. However, the magnitude of the friction force itself depends on the normal force, and hence the mass of the rubber.

Think about it this way. A brick has a skinny side and a wide side. When on the skinny side, the weight of the brick is displaced over that small amount of surface area. If you turn the brick so it lays on the wide side, there is a greater surface area but less weight per square inch of the brick that touches the table. Since the weight distribution balaces out the friction added by the surface area, the surface area does not affect the friction.


ahhh. i can set down my nerd spectacles now.
 

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You all miss the real reason why wide tires stick better. The cf has little to do with it. A tire grips by gripping, that is the rubber deforms around the pavment matrix edges and hold the tire from sliding. A larger contact patch = more surface to grip with.

SImple.

FOG
 

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FOG said:
You all miss the real reason why wide tires stick better. The cf has little to do with it. A tire grips by gripping, that is the rubber deforms around the pavment matrix edges and hold the tire from sliding. A larger contact patch = more surface to grip with.

SImple.

FOG
LMAO!!!! who can argue with that?
 
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FOG said:
You all miss the real reason why wide tires stick better. The cf has little to do with it. A tire grips by gripping, that is the rubber deforms around the pavment matrix edges and hold the tire from sliding. A larger contact patch = more surface to grip with.

SImple.

FOG
smith.p.sean said:
luco.vico said:
since we are talking engineering (went there too), and since this discussion is getting a bit theoretical, maybe someone can explain to me the whole 'wider' tire and bigger contact patch idea for better friction. The force of friction is the coefficient of friction multiplied by the Normal Force. Nowhere does the surface area come into play. I have puzzled with this for a while, and have asked a couple of profs, but never got a good answer.
Coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large rubber patch has the same coefficient of friction as a small rubber patch. However, the magnitude of the friction force itself depends on the normal force, and hence the mass of the rubber.

Think about it this way. A brick has a skinny side and a wide side. When on the skinny side, the weight of the brick is displaced over that small amount of surface area. If you turn the brick so it lays on the wide side, there is a greater surface area but less weight per square inch of the brick that touches the table. Since the weight distribution balaces out the friction added by the surface area, the surface area does not affect the friction.


ahhh. i can set down my nerd spectacles now.
thats not true fog...

he specifically asked WHY that is not true and my quoted section is the reason WHY that is not true. Coefficient of friction has everything to do with it. Grips by gripping?? with what? magic grip, no friction.
 

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I don't think anyone is going to really argue that it's not the force of static friction that keeps the tire on the pavement. And the real life situation, where the tire deforms and the pavement surface is not even, is a lot more complicated than a block diagram from physics class with a vector normal force (usually expressed as mg on a flat surface).

Sean, what you are describing with the brick example seems more like friction is a function of pressure (weight per sq.in)...but pressure is a function of mass and surface area. Or were they oversimplifying things in class?
 
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luco.vico said:
I don't think anyone is going to really argue that it's not the force of static friction that keeps the tire on the pavement. And the real life situation, where the tire deforms and the pavement surface is not even, is a lot more complicated than a block diagram from physics class with a vector normal force (usually expressed as mg on a flat surface).

Sean, what you are describing with the brick example seems more like friction is a function of pressure (weight per sq.in)...but pressure is a function of mass and surface area. Or were they oversimplifying things in class?
i simplified it for you because the block is very easy to understand. were not looking for pressure we are looking for force. F= massxaccerleration

What is Normal Force? N = mg. Massxgravity.

if you read the top half its fairly unsimplified and explains exactly what the block explains.


Coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large rubber patch has the same coefficient of friction as a small rubber patch. However, the magnitude of the friction force itself depends on the normal force, and hence the mass of the rubber.

It doesnt matter if there is a sliver of tire or 10 square feet of tire on the ground. if the mass is the same between the two tires and its the same compound. Same exact friction will be there.


different tire compounds have different coefficients of friction ie soft slicks vs hard touring tire.
 

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smith.p.sean said:
Coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large rubber patch has the same coefficient of friction as a small rubber patch. However, the magnitude of the friction force itself depends on the normal force, and hence the mass of the rubber.

It doesnt matter if there is a sliver of tire or 10 square feet of tire on the ground. if the mass is the same between the two tires and its the same compound. Same exact friction will be there.


different tire compounds have different coefficients of friction ie soft slicks vs hard touring tire.
That makes perfect sense...exactly what I thought. So then why have I read that a tire that is slightly deflated will have better grip (but will wear faster) if it's the same tire and same bike? Or are they just plainly wrong?
 
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luco.vico said:
smith.p.sean said:
Coefficient of friction is not a function of mass or volume; it depends only on the material. For instance, a large rubber patch has the same coefficient of friction as a small rubber patch. However, the magnitude of the friction force itself depends on the normal force, and hence the mass of the rubber.

It doesnt matter if there is a sliver of tire or 10 square feet of tire on the ground. if the mass is the same between the two tires and its the same compound. Same exact friction will be there.


different tire compounds have different coefficients of friction ie soft slicks vs hard touring tire.
That makes perfect sense...exactly what I thought. So then why have I read that a tire that is slightly deflated will have better grip (but will wear faster) if it's the same tire and same bike? Or are they just plainly wrong?
itll def wear faster with a larger contact patch however the added grip is simply misunderstanding, the exact thing fog said... he may be able to whoop my ass in some twisties but i know my physics.

larger contact does not = more grip. better coefficient of friction= more grip. more mass = more grip.
 

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Ok, good! I won't have to go kick my physics teacher's ass. ;D
 
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luco.vico said:
Ok, good! I won't have to go kick my physics teacher's ass. ;D
Ever heard of a tire manufacturer saying this? Ever read it in your vehicle manual :) .

You should kick his ass ne ways. Physics teachers are the devil.
 

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smith.p.sean said:
Ever heard of a tire manufacturer saying this?
nope...
 

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The grip is from the rubber deforming around the pavement particles . that why the softer the rubber the better he grip. If it was all up to CF you couldn't drive inn the rain.

FOG
 
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FOG said:
The grip is from the rubber deforming around the pavement particles . that why the softer the rubber the better he grip. If it was all up to CF you couldn't drive inn the rain.

FOG
no way. since when does rain get rid of friction? It doesnt man. softer rubber (better tires) gives a better coefficient of friction.
 

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you take a super soft qualifier slick on a wet track, you do poorly.
you take a rain tire out, you do well.

What does a super soft rain tire do that a super soft slick cannot? evacuate water by sealing the rubber and the road together and squeeze the water out, like toothpaste.

the presence of water will ALWAYS reduce friction because of surface tention and it's ability to fill in the road imperfections (which is what rubber needs to gain traction). without that, you might as well be on glass.

Remove the water, replace it with rubber. instant formula for traction.
 

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The friction coefficient is reduced with the introduction of water...it's really a function of the two surfaces doing the friction...oil will reduce it...water will...and a bunch of other 'slippery' things. Right??
 

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'But but but the caliper is attached to the fork. Indeed it is. However because both sides of the pads apply equal forces to the rotor the system is contained inside of the caliper. The caliper centers itself over the rotor.'

No, no, NO! The 'force' is contained within the front tyre contact patch with the road, (or else you wouldnt stop!) The caliper is mounted to the rear section of the fork leg. The brake rotor spins from 'bottom' to 'top' of the fork (in a rotary motion). The caliper transmits its force into the fork leg in an upwards and rearwards direction, (the vector diagram gets real complicated depending on the force of braking and the varying friction levels of the tyre contact patch). This means that a single disk machine will try to move one fork leg in a different direction to the unbraked fork leg. This force is contained by the wheel spindle and any fork brace conecting the two independant sructures (fork legs). As everything on our example (the GPZ) is built on the flimsy side of flimsy, I would have thought that a twin disk set-up would have been one of the first mods to be explored. The example of the Buell single disk merely reinforces my point, those have fork leg diameters approaching tree trunk girth, all firmly clamped together, its not beating Newton, just over-engineering to combat the unequal forces.
 

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Jesu fucking Christo, I can't believe I just read that whole thread...you geektastic lunatics.

Alright, in order of importance:

1) Tswami, you are hereby elevated to honorary member of Team Villain, on account of your fearless cock-measuring against my avowed nemesis Forbin (who I'm way faster than, send tire warmer funds to [email protected]), and your display of general prickishness in the face of adversity and high post counts, all while maintaining a degree of eloquence. Congratulations.

2) As to the meat of the original query, a single disc and caliper - even the stock pieces - are strong enough to lock the front wheel. This is the absolute limit of traction of the tire, and if you lock the wheel you have reached it and can go no further. The largest practical benefit of dual discs (or larger discs, or more caliper pistons, etc.) next to better heat dissipation (a mostly irrelevant detail on this machine, as it's slothful and doesn't require much braking, therefore generates little brake heat), is that the additional surface area allows the user to more easily control the braking force right up to the point of lockup without reaching it. You're not getting more stopping power with dual discs, you're getting a broader feel, helping you to better use them.

That being said, there's not much to be gained from those benefits on this particular motorcycle. The single-disc setup - if augmented with a floating disc, good pads, kevlar or steel lines, and quality fluid - actually provides pretty good feel, and the ability to modulate braking forces without overwhelming the tire. The speeds the EX is capable of reaching (maybe 115 if geared for it?) don't necessitate the sort of crisis braking that a more modern sportbike needs to be able to cope with (say, hauling down from 165mph).

Of course all my practical knowledge is biased in coming from the world of riding these motorcycles around a racetrack...clearly not the environment to which they were designed. If you're just going to tour the thing, I say why not get as many brakes as you can under you. Triple disc! Quadruple! And ABS! Performance be damned! The goal apparently being to get away without grabbing a fistful of brakes and not falling down.

3) Jdugen, your argument sounds fine in theory (and by fine I mean boring), but without having nearly the sort of engineering acumen necessary to engage it on a scientific level, I can tell that in practical terms the thing you're worried about doesn't seem to have much relevance. If the two sets of triple clamps and the axle weren't enough to corral the forks into spreading unbalanced loads evenly into the motorcycle, then suspension tuners wouldn't be able to get away with running different rate fork springs in each leg to achieve a more tailored reaction. But they do, and it works.

4) I don't really have a fourth thing, so let's just sign off, shall we? Smoke crack, worship Satan.
 
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