Spaghetti

Lowering the body

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Smart man.

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I think there's a lot of emphasis on getting your head low, but that isn't everything... as Cobie alluded to, Level 3 explains everything about it. 

I would just add that it's similar to knee down - if you are trying to get your knee down - if you're trying to get your head low, then you're doing it wrong. These shouldn't be goals in themselves, but are end results of correct riding technique. ;)

Before I did Level 3 I would try and hold my body in all kinds of uncomfortable positions through the corner. Afterwards, I wasn't getting anywhere near as tired, riding took less effort and my body movement were more effective - I was overall a much better, faster rider. 

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I guess I have a question about this than. When I stared going faster I noticed I was limited when I was weighting the inside peg and basically sitting on my inside foot. Another rider told me to try holding on with my outside knee in the tank and referenced how Marquez and Rossi have there inside leg dangling until the apex basically. I have changed to this  and use my outside knee to hold my self and lean angle (not the leg dangle). 

But my question is if my only connection to the bike is weighting my outside leg and basically nothing on the inside does it really matter where my body is? Or is peg weighting more important than body position?

 

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11 hours ago, Subisti said:

........... my question is if my only connection to the bike is weighting my outside leg and basically nothing on the inside does it really matter where my body is? Or is peg weighting more important than body position?

 

 

What is important is the location of your center of gravity respect to the bike.

That center of gravity is located more or less close to your bellybutton and it is a theoretical point at which the addition of the weights of each part of your body can be considered concentrated at for any Physics calculation.  Same applies to the center of gravity of the bike alone, including all the fluids, which is located more or less by the valves.

Once your body is connected to the bike, regardless of the point(s) of contact, both CG's add up and relocate to a point between both individual GC's.  For the bike to turn in a balanced manner (leaned over), that combined CG must be aligned with a line between both contact patches.

Hanging off is moving the rider's CG towards the inside of the corner, which pushes the bike's CG towards the outside of the corner, achieving less lean angle for the chassis.

More discussion on the subject:

VehicleRollAngleRealTire2.jpgVehicleRollAngleRealTire3.jpg

 

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Thanks for those links, they are very informative. I guess maybe they make my point or at least help with my question. If center of gravity is what helps lean angle than it shouldn't matter which peg is weighted ,if your center of gravity is down between the bike and ground or up level with the tank if you are putting all your weight on the outside peg is there a difference? 

 

Maybe this is more of a compound idea with all the pieces add up to lean angle and I'm thinking of it as a single component.

thanks

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22 hours ago, Subisti said:

..........if your center of gravity is down between the bike and ground or up level with the tank if you are putting all your weight on the outside peg is there a difference?.....

That is an interesting question!

You cannot do both things at once, just like you cannot stand on one foot while your CG if way off the vertical line going through your foot.  You create pressure between tank and outside peg in order to have good traction in your outside foot, in order to lock your thigh over the seat in order to hang off the inside.  Most of your weight is actually supported by your thigh and some by the inside foot, but again, the bike does not care about the way your weight is transferred to the contact patches of the tires.

The important thing to note here is that, having only two wheels, the bike-rider assembly is always balanced (except when counter-steering), as much when leaned as when straight up.  Balanced meaning that there are no forces acting to flip the bike out of that state of balance.

When going on a straight line, the bike is balanced in a vertical position (when looking at it from the front) because gravity is pulling straight down and the CG and the points of contact of the tires must be vertically aligned.  When going around a turn, the bike is balanced in diagonal position (leaned) because the resultant force of gravity plus centrifugal acceleration is pulling in a diagonal direction and harder than gravity alone.

Because of that, you can experiment about alternating pressure on pegs and hanging off while the bike follows a straight line and you will have similar conditions than when cornering.  Observe the reactions of the bike and the involuntary steering inputs (pressure of your hands on the bar) as you do so.

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post-23333-0-23363900-1367700908_thumb.jpg.

Imagine this diagram to represent the forces on the tires when cornering (weight and centrifugal), then rotating the picture 45 degrees counterclockwise.  For Physics, the position of the bike (leaned or vertical) does not matter, only the magnitude and direction of the forces.  It is just like the bike is straight up.  Now, the rider weights one peg (standing directly above it).  How the bike will react to keep the balance?  It will lean away from the loaded peg, as much as needed to vertically align the compound CG (bike's and rider's) with the tires.  It will do that with the help of the hands of the rider, who will instinctively hang from the bar (no steering perhaps) to keep balance.

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I've got to find a way to experiment with body weight- there is still something about the whole thing nagging at me and the BS Bike video doesn't answer my questions.

@Lnewqban, you have an interesting way of explaining things and it makes sense to my left brain, but I've had some experiences that gives me cognitive dissonance.

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Sorry to chime in on this just a pet peeve... Let's go by stating there is no Centrifugal force.  Just centripetal force, which goes inward to the center of a radius of a turn, no outward force.  And please don't mention inertial reference frames, if you know what that is then you know it doesn't apply here and just trying to be difficult. And you can't just rotate the picture 45 degrees and assume forces rotate like that, gravity doesn't rotate with you so the direction of forces can't be right.

In physics the direction of the bike lean angle does matter because that DOES change the magnitude of the forces.  You lean 45 degrees, for simplicity say the CG is at 45 degrees, then the normal force applied to the tire would be COS(45)*N which is why you have less friction at lean than upright.

A lot of good info on the discussion mixed with bad physics.  You can do more explaining what you need to do to make something happen and only apply the science behind it if it's what really is happening not what we think is happening.

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4 hours ago, playersnoopy said:

Sorry to chime in on this just a pet peeve... Let's go by stating there is no Centrifugal force.  Just centripetal force, which goes inward to the center of a radius of a turn, no outward force.  And please don't mention inertial reference frames, if you know what that is then you know it doesn't apply here and just trying to be difficult. And you can't just rotate the picture 45 degrees and assume forces rotate like that, gravity doesn't rotate with you so the direction of forces can't be right.

In physics the direction of the bike lean angle does matter because that DOES change the magnitude of the forces.  You lean 45 degrees, for simplicity say the CG is at 45 degrees, then the normal force applied to the tire would be COS(45)*N which is why you have less friction at lean than upright.

A lot of good info on the discussion mixed with bad physics.  You can do more explaining what you need to do to make something happen and only apply the science behind it if it's what really is happening not what we think is happening.

You may be the perfect person for this then....I've argued the same point (not here), but honestly don't understand it myself sufficeintly - just what I've been indoctrinated with in Physics class: Centripetal vs Centrifugal force. The question is: why is Centripetal the real force and the outward movement of orbital objects that WE OBSERVE not considered a "real" or reactionary force only? Please explain why we can observe centrifugal but not observe centripetal.

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12 minutes ago, Jaybird180 said:

You may be the perfect person for this then....I've argued the same point (not here), but honestly don't understand it myself sufficeintly - just what I've been indoctrinated with in Physics class: Centripetal vs Centrifugal force. The question is: why is Centripetal the real force and the outward movement of orbital objects that WE OBSERVE not considered a "real" or reactionary force only? Please explain why we can observe centrifugal but not observe centripetal.

I'll try and explain it the best that I can.  First in any engineering physics class covering classical mechanics involving circular motions will state in the book Centrifugal "Force" in quotes usually or at least call it a fake/false force.  Second is to understand reference frames and in classical mechanics we use non-inertial reference frames.  Take an example of you standing in the back of a pickup truck doing 50mph and throwing a tennis ball off the back away from the direction of travel; and you throw this ball say 20mph.  Now you the thrower of the ball observe it clear as day moving in the opposite direction from the direction you're travelling... and at a rate of 20mph (which is correct in reference to you and the truck)... now take an observer standing off to the side of the road looking perpendicular to the road and he sees the ball still moving in the direction of the travel of the truck and you just at 30mph (which is also correct in reference to the observer).  But which is "correct"; now ignore air resistance and gravity to the mix as we're not trying to calculate the rate of decrease of the speed and arc of the motion and so on... we're applying ideal physics to understand the parts we want to figure out what's going on.

So in circular motion for an inertial reference frame one common example is that of you sitting on spinning disc (say a merry go round) and releaseing a ball on the disc and observe it in an outward motion; it's best to actually see it in effect to see how weird things get in difference reference frames... here's a video showing some non intuitive things occurring in that situation 

 

The biggest mistake the average person that doesn't have a lot of background in physics and just reads up on some aspects of it when researching circular motion is applying Newton's laws of motion incorrectly in an wrong reference frames; you probably heard people saying well yes there is this inward force called centripetal force but Newton's law says there is an equal and opposite force when not accelerating to give a net 0 force and that force is the centrifugal force.  Only correct when in the inertial reference frame for this circular motion example.

Another non intuitive mistake made is that almost all of us have been in a car at some point, and taken a turn or a curve, and we swear we are being pushed outward from the curve and that is the centrifugal force we "feel".  But it's actually inertia you're feeling.  Let's say you're in the passenger seat; on this turn (left turn) you are pushed to the door and say I'm going outward.  But in fact the car is moving inward left turn; and you are still moving forward; so naturally you hit the door.

So analyze a motorcycle taking a turn (left turn again); you know at any point you were only going straight and you added input to turn left and lean to the left.  You can say you "feel" and outward force but analyze where did this magical outward force come from; we know the downward force is from gravity (which is mysterious in itself).  When you lowside the bike and rider don't all of a sudden end up moving "outward" of the turn; they end up sliding forward (minus any weird tire contact of the wheel causing a different motion) but you get the idea.

That's about the simplest way I can try and explain it.. but you want to apply physics in the discussion from text and online sources; majority of it will be from classical mechanics which is all non-inertial reference frames.  A lot of people don't understand that part and apply intuition to the mix and confusion erupts.  I plan on posting up some videos on some of the physics misconceptions after I review CSS when I go for lvl 1+2 next week.

Personally I think a lot of the youtube instructions out there like ridesmart and individuals would do a lot better just explaining "do this to get this result" and leave out the why part; seems like 90% is accurate and then 10% is made up physics interpretation on their part and discredits the 90% they just got right.

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@playersnoopy- please stick around the forum. I like you and your explanation makes sense. The video unfortunately introduces Coriolis while failing to elucidate the orbital mechanics question as you addressed in your post. The merry-go-round (MGR) demonstration was cool and I might show this to my children but with the scarcity of MGRs we might not find a suitable place to reproduce the experiment.

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As I thought, they said they'd never been on one and don't know a playground that has one. My 7year old "correctly" observed that the ball was moving in a circular motion :-)

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On 7/21/2017 at 8:29 AM, playersnoopy said:

Sorry to chime in on this just a pet peeve... Let's go by stating there is no Centrifugal force.  Just centripetal force, which goes inward to the center of a radius of a turn, no outward force.  And please don't mention inertial reference frames, if you know what that is then you know it doesn't apply here and just trying to be difficult. And you can't just rotate the picture 45 degrees and assume forces rotate like that, gravity doesn't rotate with you so the direction of forces can't be right.

In physics the direction of the bike lean angle does matter because that DOES change the magnitude of the forces.  You lean 45 degrees, for simplicity say the CG is at 45 degrees, then the normal force applied to the tire would be COS(45)*N which is why you have less friction at lean than upright.

A lot of good info on the discussion mixed with bad physics.  You can do more explaining what you need to do to make something happen and only apply the science behind it if it's what really is happening not what we think is happening.

 

According to the headlines of this forum, we discuss "Anything that advances a rider's understanding of riding."

As the background of all posters is not the same, we should try discussing complicated subjects in the most simple and yet understandable way.

You are correct about the illusory nature of centrifugal force, as well as about the departure from the pureness of the academic discipline.

Nevertheless, in my humble opinion, it is a simple shortcut to give the idea of the experienced tendency of the mass of bike and rider to resist the curvilinear movement of cornering.

I believe that your explanation of the cornering force and having less friction when leaned is contradictory and inaccurate, as the cornering rider feels more than his/her static weight.

Copied from:

http://forums.superbikeschool.com/index.php?/topic/3723-the-1g-club/

"The barrier then is both physical sensation and visual orientation and I believe there is a make/break point in it. That point is 45 degrees of lean. At 45, the forces are a bit out of the ordinary. Along with the normal 1g down we now have a 1g lateral load as well. As a result the bike and our bodies experience an increase in weight. That’s not native to us and acts as a distraction and as a barrier." - Keith Code (2013)

As you seem to be serious about the Physics of motorcycling and able to understand complicate explanations, I highly recommend you these two books:

"Motorcycle Handling and Chassis Design: the art and science" by Tony Foale.

"Motorcycle Dynamics (Second Edition)" by Vittore Cossalter.

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4 hours ago, Lnewqban said:

"The barrier then is both physical sensation and visual orientation and I believe there is a make/break point in it. That point is 45 degrees of lean. At 45, the forces are a bit out of the ordinary. Along with the normal 1g down we now have a 1g lateral load as well. As a result the bike and our bodies experience an increase in weight. That’s not native to us and acts as a distraction and as a barrier." - Keith Code (2013)

You bring up a very good point... also I probably misspoke in terms of the loss of friction in respect to the change in the normal force.
I will say there's parts I am not very well versed when it comes to the artificial gravity experienced in circular motion so I will make statements clear when I am making assumptions and personal opinions here.  One thing to note is that first it's the increase in weight experienced by the rider not necessarily the increased in weight of the bike and the rider.  That's not to say the weight gain isn't significant; I just don't know how much... best case let's say only the wheels cause the centripetal acceleration and with the good suspension the rest of the bike and rider experiences the 1g laterally, but can't be the full weight of the bike no matter what right? (assumption). The other thing to note is I based it purely based on a horizontal flat surface of the road; where in a banked turn you definitely can go faster.  So even with the lateral g-force how much of it is affecting it in the vertical direction to affect the normal force perpendicular to the road surface to the tire; how much is the vertical component.  Assuming CG is same is the lateral g-force horizontal and parallel to the ground?  But yes the friction lost should/could be negligible even on a flat surface.

Regardless like I said you are correct I shouldn't have mentioned the friction part; as the centripetal force is what really causes the loss of friction with the velocity component being squared which is why we go slow (even though amount of friction may not have changed?).

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16 hours ago, playersnoopy said:

...... best case let's say only the wheels cause the centripetal acceleration and with the good suspension the rest of the bike and rider experiences the 1g laterally, but can't be the full weight of the bike no matter what right? (assumption). 

......  So even with the lateral g-force how much of it is affecting it in the vertical direction to affect the normal force perpendicular to the road surface to the tire; how much is the vertical component.  Assuming CG is same is the lateral g-force horizontal and parallel to the ground?  But yes the friction lost should/could be negligible even on a flat surface.

....... as the centripetal force is what really causes the loss of friction with the velocity component being squared which is why we go slow (even though amount of friction may not have changed?).

I believe that your above assumptions are correct, playersnoopy.

While following any circular trajectory, what the rider feels on his body (against seat, tank, pegs and grips) is a force that is greater than his natural weight, which is nothing more than the vertical force resulting from the action of gravity (1 g) over his body mass.  That additional force comes from the vectorial combination of natural acceleration (gravity) (Fg=mg) and centripetal acceleration (Fc=mV^2/r) over his/her body mass.  The direction of that resultant force (Fr=square root[Fg^2+Fc^2])is more or less aligned with the lean angle because the contact patches are the only point of support and the bike must be in dynamic balance.

Regarding maximum attainable tire's grip (to resist centripetal-induced-force), it should be proportional to the weight of the bike plus rider before they start moving and proportional also to the tires' contact patches.  That weight is the mass of both combined with the vertical g, which oscillates around the magnitude of the natural gravity (g=32.2 ft/sec^2) while the bike rolls over the irregularities of the pavement.  After a crest G<g (the bike+rider are moving down and weight less = less friction or traction on the contact patch to fight the lateral G).  After a valley G>g (the bike+rider are moving up and weight more = more friction or traction on the contact patch).

Some tires have a bigger contact patch as they lean.  After several laps of a fast race, the rubber on the sides starts deteriorating, which may cancel the gain in area of the contact patch.

I believe that the posts of this old thread will result interesting to you:

http://forums.superbikeschool.com/index.php?/topic/3331-have-you-ever-slid-the-front-without/

Free body schematic.JPG

G force vs Lean Angle.JPG

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For me, weighting the pegs makes the bike respond quicker to inputs.

Instead of changing c of g, which physically is not possible by changing your attachment point, i think the benefit of weighting pegs has to do with removing your dead weight from the seat and allowing your own suspension (ankle, legs, hips) to take up some of the work of moving the bike. Decoupling your mass from the bikes mass to a small degree.

It is noticeable and dramatic for me, cornering with your butt planted in the seat and cornering weighting the pegs.

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8 hours ago, jcw said:

For me, weighting the pegs makes the bike respond quicker to inputs.

Instead of changing c of g, which physically is not possible by changing your attachment point, i think the benefit of weighting pegs has to do with removing your dead weight from the seat and allowing your own suspension (ankle, legs, hips) to take up some of the work of moving the bike. Decoupling your mass from the bikes mass to a small degree.

It is noticeable and dramatic for me, cornering with your butt planted in the seat and cornering weighting the pegs.

Is it possible that the change in position results in better leverage at your elbows being transmitted into the bars?

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31 minutes ago, Jaybird180 said:

Is it possible that the change in position results in better leverage at your elbows being transmitted into the bars?

Possibly...

But the position is not much different. 

I admit I don't fully understand it. I mean the leg dangle guys don't mind sitting firmly on the seat on corner entry. But I'd bet on side to side transitions, when they need most bar input, they are light on the seat.

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On 7/23/2017 at 7:20 AM, Lnewqban said:

Regarding maximum attainable tire's grip (to resist centripetal-induced-force), it should be proportional to the weight of the bike plus rider before they start moving and proportional also to the tires' contact patches.  

Slightly off topic, but this is not correct.  The contact patch size has no impact on traction.  It is a complex topic, and I like this explanation best http://www.stevemunden.com/friction.html.

The second law of friction states "Friction has no relation to contact surface area".  Friction depends entirely on the Force (not pressure) applied between the two surfaces. If we assume the rubber compound and road surface of both tires are the same at any given point in time, the grip on front and rear has nothing to do with the size of the contact patch and only to do with the amount of force applied.   Moving around on the bike changes the forces applied to the tire and the MotoGP style uses less of the available friction than other styles - it is not because the contact patch is different specifically.  The grip at all angles of lean on the same tire on the same surface is the same.

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If that didn't compute for some folks, remember friction is proportional to the normal force applied between the two surfaces.  On a flat road, that only comes from Gravity.  On a banked corner just standing still you feel like you might slip down, because you have less friction (Gravity is not perpendicular to the surface, so you have less force creating less friction).  When you ride at speed around a banked turn you get more friction leaned over because some of the inertia will add to the normal force and increase friction.  This is why you can go faster on a banked turn.  Likewise, as stated in Twist II, as you come off a banked turn you need to watch your lean angle, because friction will reduce and therefore your demands on grip might exceed what you have.  I don't think it actually because the lean angle increases, for if you are on the same arc and have the same lateral forces applied your demand for grip has not changed, but it is because the amount of grip available decreases.

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46 minutes ago, ausrobbo said:

Slightly off topic, but this is not correct.  The contact patch size has no impact on traction.  It is a complex topic, and I like this explanation best http://www.stevemunden.com/friction.html.

The second law of friction states "Friction has no relation to contact surface area".  Friction depends entirely on the Force (not pressure) applied between the two surfaces. If we assume the rubber compound and road surface of both tires are the same at any given point in time, the grip on front and rear has nothing to do with the size of the contact patch and only to do with the amount of force applied.   Moving around on the bike changes the forces applied to the tire and the MotoGP style uses less of the available friction than other styles - it is not because the contact patch is different specifically.  The grip at all angles of lean on the same tire on the same surface is the same.

I know that's what physics says but the guys that do drag racing have a different experience. They put the widest tires they can muster on the rear of the car/bike to increase contact patch. The result is better ability to put power to the ground.

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1 hour ago, Jaybird180 said:

I know that's what physics says but the guys that do drag racing have a different experience. They put the widest tires they can muster on the rear of the car/bike to increase contact patch. The result is better ability to put power to the ground.

The problem with contact patch is majority of racing community (motorcycle, car, drag) don't have the correct understanding of it; because they get their info from other people in that community that also got it wrong to begin with (ie. "my tire guy said..." or "(some famous racer or person involved in the community) said this and I'm going to take his word over something from physics" which then follows up with "yeah that may be true on paper but in the real world there are a lot of other things going on and I know contact patch gives better grip").  Personally I always feel someone loses credibility when they say more contact patch gives more grip.  As for the drag racing guys here's an article from someone in drag racing giving his explanation and clearly stating contact patch is does not give more grip but for shearing purposes and pressure.  http://www.onallcylinders.com/2016/07/14/drag-slicks-traction/

One could go on stating contact patch and larger contact patch is a good thing and leave out any physics aspect of it; don't ever say gives more grip and would be 100% correct.  But they go on to give the "science" explanation for no reason w/o knowing any science but what they heard or read on some forums and give the wrong information to many innocent bystanders.

In fact if you take any classical mechanics in physics and get to the chapter on friction most common question in class given to students is "If the friction force equation is solely dependent on the coefficient of friction and the normal force and has no input based on the size of the contact to the surface then why do race cars have larger tires?"  I promise almost everyone taking physics google this question and most information out there especially on forums including physics forums get it wrong.  For those that say it's to get more grip; all you need to do is ask where did they learn that from?  It's never from a physics class.  You can watch the MIT Physics class on youtube that covers this exact topic and that question being asked as an assignment.

Just know contact patch does not give more grip... but contact patch is important and you want to have the largest contact patch possible (for the most part).  As for why it's important if you really care it's primarily for pressure.  When dealing with fields like drag cars, and to some extent with motorcycles with softer compounds it also has to do w/ shearing.

Sorry just a pet peeve of mine -.-  (something CSS UK at some seminar also got wrong w/ some tire rep at an expo; need to find that video link)

P.S. on a side note... not one instructor at CSS lvl 1+2 at NJMP said this so I was very pleased :)  They left it at more contact patch and nothing else (intentional or not).  See you guys at NJMP again in a little over a week.

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22 minutes ago, playersnoopy said:

The problem with contact patch is majority of racing community (motorcycle, car, drag) don't have the correct understanding of it; because they get their info from other people in that community that also got it wrong to begin with (ie. "my tire guy said..." or "(some famous racer or person involved in the community) said this and I'm going to take his word over something from physics" which then follows up with "yeah that may be true on paper but in the real world there are a lot of other things going on and I know contact patch gives better grip").  Personally I always feel someone loses credibility when they say more contact patch gives more grip.  As for the drag racing guys here's an article from someone in drag racing giving his explanation and clearly stating contact patch is does not give more grip but for shearing purposes and pressure.  http://www.onallcylinders.com/2016/07/14/drag-slicks-traction/

One could go on stating contact patch and larger contact patch is a good thing and leave out any physics aspect of it; don't ever say gives more grip and would be 100% correct.  But they go on to give the "science" explanation for no reason w/o knowing any science but what they heard or read on some forums and give the wrong information to many innocent bystanders.

In fact if you take any classical mechanics in physics and get to the chapter on friction most common question in class given to students is "If the friction force equation is solely dependent on the coefficient of friction and the normal force and has no input based on the size of the contact to the surface then why do race cars have larger tires?"  I promise almost everyone taking physics google this question and most information out there especially on forums including physics forums get it wrong.  For those that say it's to get more grip; all you need to do is ask where did they learn that from?  It's never from a physics class.  You can watch the MIT Physics class on youtube that covers this exact topic and that question being asked as an assignment.

Just know contact patch does not give more grip... but contact patch is important and you want to have the largest contact patch possible (for the most part).  As for why it's important if you really care it's primarily for pressure.  When dealing with fields like drag cars, and to some extent with motorcycles with softer compounds it also has to do w/ shearing.

Sorry just a pet peeve of mine -.-  (something CSS UK at some seminar also got wrong w/ some tire rep at an expo; need to find that video link)

P.S. on a side note... not one instructor at CSS lvl 1+2 at NJMP said this so I was very pleased :)  They left it at more contact patch and nothing else (intentional or not).  See you guys at NJMP again in a little over a week.

To serve what purpose?

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20 minutes ago, Jaybird180 said:

To serve what purpose?

Pressure... bigger the tire the more pressure it can handle.  Ignore street riding where tires don't heat up as much as racers on a track and temperature/pressure (direct linear correlation) becomes a major issue for the tires.  Heat building up inside the tire creates more pressure; pressure is also the force over an area so the smaller the contact patch the more pressure on the tires once again... nobody wants a blowout http://www.autosport.com/news/report.php/id/122707.  Of course heat on the exterior of the tire and shearing also becomes an issue and you can control it to an extent w/ the size of the contact patch but becomes a careful balance; which is why in this regard I said larger contact patch is better for the most part.

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