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Why Are We Weighting The Outside Peg?

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With the bike leaned over and with any decent speed (say over 50mph) how much will it matter which peg is weighted? Both are connected to the frame...any engineers want to take as stab a this? (try to esplain in real English for the geometrically challenged).

 

CF

 

Well from a bio-mechanical point of view I think weighting the inside peg makes it impossible to lock your outside leg into the fuel tank. If you have your inside knee out and your weighting the inside peg it would dislodge your lower body's lock onto the motorcycle. That would force you to hold onto the handlebars which can potentially make the bike very unstable.

 

From a mechanical point of view the point of hanging off the motorcycle is to increase gravity's leverage on pulling the motorcycle to the ground. That single aspect lets you go around a corner at the same speed only with less lean angle on the bike. By weighting the outside peg and locking your leg into the fuel tank there is much more leverage that your body has on the motorcycle compared to leaving your weight on the inside peg. It makes your hanging off body position more efficient to get the desired effect and weighting the outside peg lets you keep your lower body much more stable on the motorcycle.

 

For accelerating having your weight on the pegs will lower the CG of the bike. This helps keep the front tire on the ground under hard acceleration. I don't think thats very useful on a 600cc sportbike but for 750cc+ it can be tough to keep the front tire on the ground.

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With the bike leaned over and with any decent speed (say over 50mph) how much will it matter which peg is weighted? Both are connected to the frame...any engineers want to take as stab a this? (try to esplain in real English for the geometrically challenged).

 

CF

 

Ahhhh... just to clarify I have only been talking specifically about reduced traction situations like hard acceleration (enough to make the tyre slip), or riding on dusty/sandy/dirty surfaces.

 

If we're just talking about a relatively sedate ride, not pushing the limits of traction, then in that case I'd say no - peg weighting would have (very) minimal effect, if any.

 

Some years ago after I read about outside peg weighting, I used to think that somehow taking weight off it would be bad (causing a loss of traction). Well I eventually got over that idea. I remember one WSBK race, it was the final chicane at Magny-Cours and Troy Bayliss (probably his last year in WSBK) was exiting that section and as he was making the final left corner his outside foot came off the peg. Of course that means that he would have been using a fair amount of weight on the inside peg to hold himself on the bike, and he didn't crash. Which put paid to the idea that the outside peg needs to be weighted all the time while the bike is leant over.

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I am not a physicist (actually a chemist) so correct me if I am wrong .. weighting the inside or the outside peg DOES NOT change your body's CG and hence cannot change the overall(bike+rider) CG of the bike

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OK, I'll take a shot at this; not sure I can manage plain English, though. :) First, let's tackle weighting the pegs (either, or both) as opposed to sitting with all your weight on the seat. When you need to steer the bike, you have to lean it over, or rotate it about its roll axis. Putting weight on the pegs instead of on the seat puts your weight closer to the center of mass which makes it easier to steer the bike, because the bike rotates around the center of mass. (As Keith puts it in Twist II, "The center of mass is the part of the bike that moves the least, so getting your weight closer to it means you have to move that weight less distance"- see page 85 in Twist of the Wrist II.)

If the bike and rider form a rigid body (rider is locked-on the bike) then the center of mass and inertial moment are independent of the attachment point. Now if the rider lays down on the tank instead of sitting upright this will get the rider's mass closer to the bike's center of mass.

 

Hypothetically, once the bike is leaned over, putting more weight on the inside peg would put the weight lower than putting it on the outside peg, and possibly that could help tighten your line - however you are talking about trying to overcome substantial gyroscopic forces, so unless you are going paralyzingly slow, I don't think it would make very much difference - certainly not enough to overcome the better BODY stability and anchor points we get from putting weight on the outside peg instead.

With the rider locked-on, the net forces on the bike are determined only by the rider's relative position w.r.t. the bike. A lateral displacement of the rider to the inside does have a a slight leaning effect, which is the equivelent of a streering torque of +1..4 Nm. Since most bikes have a small negative steering torque at typical lean angles and path curvatures, an optimal hang-off position will completely balance the steering torque, resulting in neutral steering.

 

Weighting the outside peg helps you get a very strong pivot point from which to initiate your counter-steering effort (which of course takes more effort if you are going fast), and this aspect is so important that I think it far outweighs any marginal benefit you could get from weighting the inside peg. I also think switching weight from one peg to the other mid-turn (to try to tighten your line) could cause instability in your body and thus possibly wiggle the bike, not desirable mid turn.

IMHO the only use of peg weighting is for pivot steering.

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im guesstimating COG too.

 

a lower perceived COG for the whole bike's system while in a turn will lay down more anti wheelie ballast, hence driving the front and rear down more when under power = bigger /more contact patch = more traction?

 

my 2C~

 

I've been in the very unfortunate situation to slide steer my bike to avoid head on collisions 3 times on public roads and

 

weighting in the inside helped the rear sliding wheel (from brake lockup) steer like supermoto (it steps out in the direction opposite to where im pointing) and create an "in in in" line for me for 3 seconds.

 

I see an escape line, i roll on and avoid getting squished like a bug on the windscreen = ="

 

 

thats just me, could be wrong too thou :P

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With the rider locked-on, the net forces on the bike are determined only by the rider's relative position w.r.t. the bike. A lateral displacement of the rider to the inside does have a a slight leaning effect, which is the equivelent of a streering torque of +1..4 Nm. Since most bikes have a small negative steering torque at typical lean angles and path curvatures, an optimal hang-off position will completely balance the steering torque, resulting in neutral steering.

 

Hey, no cheating. People like me require 'plain english', please. laugh.giftongue.gif

 

I'm a bit confused by your last sentence... do you agree that a motorcycle with a constant speed requires no steering input to maintain a path through a corner?

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Thinking about the question of peg weighting when leaned over at speed, the best explanation of the effect on traction that I can come up with is the 'box' analogy I mentioned on the previous page. Hopefully this diagram will better explain my reasoning:

 

kV5D8.jpg?1?3577

 

 

Thinking at extremes makes it easier for me to understand, so imagine that the rider in the above picture is right on the limit of traction. If you look at the angle of the outside peg to the tyre contact patch - it's basically straight on top of it. If I can use the 'box' analogy again - weighting the outside peg would be the equivalent of pushing down on the top of the box, which isn't very likely to make the box slide along the floor.

 

But if you look at the inside peg, any weight there will practically be pushing at the contact patch from the side. This would be the equivalent of pushing on the side of a box - it's going to slide along the floor.

 

Does that make sense? What do you think?

It's entirely possible that I have it completely wrong as well! ohmy.gifbiggrin.gif

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Thinking about the question of peg weighting when leaned over at speed, the best explanation of the effect on traction that I can come up with is the 'box' analogy I mentioned on the previous page. Hopefully this diagram will better explain my reasoning:

 

kV5D8.jpg?1?3577

 

 

Thinking at extremes makes it easier for me to understand, so imagine that the rider in the above picture is right on the limit of traction. If you look at the angle of the outside peg to the tyre contact patch - it's basically straight on top of it. If I can use the 'box' analogy again - weighting the outside peg would be the equivalent of pushing down on the top of the box, which isn't very likely to make the box slide along the floor.

 

But if you look at the inside peg, any weight there will practically be pushing at the contact patch from the side. This would be the equivalent of pushing on the side of a box - it's going to slide along the floor.

 

Does that make sense? What do you think?

It's entirely possible that I have it completely wrong as well! ohmy.gifbiggrin.gif

 

definitely makes sense and the picture makes it even more plausible. :)

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I'm a bit confused by your last sentence... do you agree that a motorcycle with a constant speed requires no steering input to maintain a path through a corner?

I agree with the technique of one steering input and then relax through the corner.

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Thinking about the question of peg weighting when leaned over at speed, the best explanation of the effect on traction that I can come up with is the 'box' analogy I mentioned on the previous page. Hopefully this diagram will better explain my reasoning:

 

kV5D8.jpg?1?3577

 

 

Thinking at extremes makes it easier for me to understand, so imagine that the rider in the above picture is right on the limit of traction. If you look at the angle of the outside peg to the tyre contact patch - it's basically straight on top of it. If I can use the 'box' analogy again - weighting the outside peg would be the equivalent of pushing down on the top of the box, which isn't very likely to make the box slide along the floor.

 

But if you look at the inside peg, any weight there will practically be pushing at the contact patch from the side. This would be the equivalent of pushing on the side of a box - it's going to slide along the floor.

 

Does that make sense? What do you think?

It's entirely possible that I have it completely wrong as well! ohmy.gifbiggrin.gif

 

definitely makes sense and the picture makes it even more plausible. :)

 

If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?

 

CF

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Thinking about the question of peg weighting when leaned over at speed, the best explanation of the effect on traction that I can come up with is the 'box' analogy I mentioned on the previous page. Hopefully this diagram will better explain my reasoning:

 

kV5D8.jpg?1?3577

 

 

Thinking at extremes makes it easier for me to understand, so imagine that the rider in the above picture is right on the limit of traction. If you look at the angle of the outside peg to the tyre contact patch - it's basically straight on top of it. If I can use the 'box' analogy again - weighting the outside peg would be the equivalent of pushing down on the top of the box, which isn't very likely to make the box slide along the floor.

 

But if you look at the inside peg, any weight there will practically be pushing at the contact patch from the side. This would be the equivalent of pushing on the side of a box - it's going to slide along the floor.

 

Does that make sense? What do you think?

It's entirely possible that I have it completely wrong as well! ohmy.gifbiggrin.gif

 

Is this a pic from your recent track day following CSS L1?

 

For simplicity let's assume the knee and elbow sliders are just hovering above the surface. As a consequence of Newton's Third Law, it is not possible for the rider to exert a net lateral force on the bike as there is no counter force. That is, nothing to press against. The rider's weight (vertical force of gravity, downward) is countered by an equal force of the bike pressing against the rider vertically (upward). There is a net torque which results from the offset of the point of application of the vertical forces.

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If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?

 

CF

 

I don't think so, Imagine there is a bump on the road and you go over it, when you're on the outside peg you're counteracting the force (caused by the bump) going up and you are pushing the rear tire down. When you're on the inside peg you not counteracting the force caused by the bump at all.

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If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?

 

CF

 

Think of holding up a barbell with only one hand in the middle of the bar. If you put 10 lbs at either end, you get a total force of 20 lbs pushing down on your wrist. If you put 20 lbs on ONE end and none on the other end, you still have 20 lbs pushing down on your wrist, but now the bar will exert a twisting motion on your wrist because one side is weighted more than the other. That's why I think weighting the inside peg more could produce a "roll" torque - the twisting force you'd feel in your wrist.

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Is this a pic from your recent track day following CSS L1?

 

 

No, not me. laugh.giftongue.gif

I'm still working towards that...

It's interesting to note that despite riding faster now than ever before, I'm yet to put my knee down. (Not that 'knee down' is a goal for me, it will just happen when it happens.) It's a funny thing that when you start riding effectively you don't use as much lean angle etc. Riding faster and faster, yet keeping more and more lean angle & safety margin in reserve... But that would be a subject for an entirely new thread...

 

If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?

 

CF

 

This may not be an accurate way to think about it, since a bike always has cornering forces applied - but... I visualise the red lines in the above diagram as an actual physical structure, say it was created out of steel tube. Now if you set it on the ground and try to balance on it - which peg will you use? You could probably succeed using the 'outside peg', but if you try to balance on the 'inside peg' leant over like that... not a chance. That's a very simplistic example relating to stability, but may not even be valid once you factor in cornering forces...

 

Great example with the barbell, Hotfoot. Makes sense to me.

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After 20 years of trackdays, i found out that static loading of one of the pegs doesn't do anything (Cog of your body stays the same)

But...only during the pick up out of a corner I momentarily apply outside peg pressure, lean my upper body even more inwards ( that's where the force on the peg is coming from/for ) and pull on the inside bar. This stand up the bike fast and makes it possible to apply the throttle a bit sooner and it feels fast and solid, even when the bike starts to slide a little.

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Thinking about the question of peg weighting when leaned over at speed, the best explanation of the effect on traction that I can come up with is the 'box' analogy I mentioned on the previous page. Hopefully this diagram will better explain my reasoning:

 

kV5D8.jpg?1?3577

 

 

Thinking at extremes makes it easier for me to understand, so imagine that the rider in the above picture is right on the limit of traction. If you look at the angle of the outside peg to the tyre contact patch - it's basically straight on top of it. If I can use the 'box' analogy again - weighting the outside peg would be the equivalent of pushing down on the top of the box, which isn't very likely to make the box slide along the floor.

But if you look at the inside peg, any weight there will practically be pushing at the contact patch from the side. This would be the equivalent of pushing on the side of a box - it's going to slide along the floor.

 

Does that make sense? What do you think?

It's entirely possible that I have it completely wrong as well! ohmy.gifbiggrin.gif

 

My question in all of this isn't why buy how? From the picture it looks impossible to place any weight on the outside peg at this time. The riders weight is on the otherside of the bike. The act of hanging off can be started with the outside peg but can't remain there, can it? I have never had a bike at anything closer to this angle so need help understanding the principle.

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Is this a pic from your recent track day following CSS L1?

 

 

No, not me. laugh.giftongue.gif

I'm still working towards that...

It's interesting to note that despite riding faster now than ever before, I'm yet to put my knee down. (Not that 'knee down' is a goal for me, it will just happen when it happens.) It's a funny thing that when you start riding effectively you don't use as much lean angle etc. Riding faster and faster, yet keeping more and more lean angle & safety margin in reserve... But that would be a subject for an entirely new thread...

 

If we separate the lock on part from this question and just look at the weighting, since both pegs are connected to the frame, doesn't that minimize the importance of where the weight goes?

 

CF

 

This may not be an accurate way to think about it, since a bike always has cornering forces applied - but... I visualise the red lines in the above diagram as an actual physical structure, say it was created out of steel tube. Now if you set it on the ground and try to balance on it - which peg will you use? You could probably succeed using the 'outside peg', but if you try to balance on the 'inside peg' leant over like that... not a chance. That's a very simplistic example relating to stability, but may not even be valid once you factor in cornering forces...

 

Great example with the barbell, Hotfoot. Makes sense to me.

 

I think one thing being left out here is that you're body weight isn't working any differently while cornering as it is while riding upright. I'm having a hard time finding a way to explain this but I'll give it a try. At a 45 degree lean angle you have about 1G of cornering force and as always 1G of gravity pulling you straight down. That means you're body weight is more or less pushing on the motorcycle the same way it does as if you were riding straight! So whether you push on the inside or the outside peg its having nearly the exact same effect on the rear tire. In other words pushing on the outside peg isn't pushing "down" on the rear tire, its pushing it out in the same way pushing on the inside peg would. I suppose you could torque the chassis a little bit but wouldn't it have the same effect as making a tiny counter-steer input? However, since your body weight is hanging off the inside that leaves you with nothing to push with on the outside. If you look at the rider's body position all of his weight is centered over his inside leg, that would leave him with nothing to push on with his outside leg without compermising his body position.

 

When you get into the realms of MotoGP that would add another dynamic to it. Cornering at 2G you are pretty much stuck to the bike even if you aren't holding onto anything. I suppose that might give you some ability to push on the outside peg no matter where your body position is. The only question I still can't answer is why? What would be the advantage?

 

I know when I lock my outside leg into the bike it "feels" like I'm weighting the outside peg. I know its only because my knee is jammed into the tank and my toe is pushing down on the peg but it does feel like I'm weighting the peg. Having my lower body locked onto the motorcycle this way really helps me get my arms relaxed mid corner and I immediately feel the bike cornering easier and sharper.

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I think one thing being left out here is that you're body weight isn't working any differently while cornering as it is while riding upright.........

 

Very well put, Fajita !!!

 

The only exception is that you and your bike "weight" more in the direction pointing toward the line between the contact patches of your tires.

 

See these diagrams:

 

http://forums.superb...t=40#entry26802

 

At 45 degrees, that dynamic weight is 40% higher than your static weight.

 

"Once we become comfortable with 45 degrees and attempt to go beyond that, the process begins to reverse. Immediately we have more lateral load than vertical load, and things begin to heat up. Riders apparently have difficulty organizing this. Suddenly, we are thrust into a sideways world where the forces escalate rapidly. While it takes 45 degrees to achieve 1g lateral, it takes only 15 degrees more to experience nearly double that (depending on rider position and tire size)." - Keith Code

 

http://www.motorcycl...aning_the_bike/

 

Now, regarding the effectiveness of loading either peg, read the following article after you have visualized that the directions of all the forces acting during turning any motorcycle are equivalent to the directions of the forces acting during riding along a slope in a straight line (see attached diagram):

 

http://www.superbikeschool.com/machinery/no-bs-machine.php

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

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Just my 2 cents... The gyroscopic and cetrifugal forces on the bike in the turn will far outweighs the marginal weight transfer applied when pushing in the peg. Much of the downward force applied by your weight is being transferred to the bike at its COG and thus completely muted. In fact, I'd venture to say that the vast majority is actually dissipated through the peg such that, if you we're strong enough, you could break the peg off the frame.

 

The real point, IMEHO, is bio-mechanical in nature. Look at a boxer when he throws a punch. A straight arm left requires him to push off on the right foot, while slightly pivoting inwards with the left. This causes the 'core' muscles of the thorax, the hip flexors, pecs, lats and even traps to help generate power, while the bones transfer the force, multiplying it and concentrating it into the hand and, thus, into the target. Like the old Karate adage says, your power comes from the ground.

 

It's is the exact same theory at work here. Except on a moving motorcycle, there is no ground from which to draw power. So we substitute with pegs instead. Pressing against the peg engages the entire leg: quads, hams, hip flexors, adductors, abductors, everything. That's what locks you into the bike. From the obliques and lower back, through the last, intercostal a, deltoids and the rest of the arm, we get a tremendous amount of power we can use to counter steer the bike. In fact, geometrically more power is generated this way than from the arm alone, as one would expect when using 'traditional' counter steering technique.

 

Lastly, by engaging the core, and the largest, most powerful and aerobic ally most capable muscles in the body, we gain the added benefit of being able to do it continuously for extended periods of time with little to no fatigue. Consider how much more energy and aerobic capacity is required to simply walk around the block. As we walk, the hips rotate forwards whole the shoulder routes back.

 

If you we're to draw a line from the shoulder to the hip, first left to right, then right to left, you'd find an 'X' formed where the intersection of the X is right around the sternum, which is actually the center of balance,in the human body, while the center of gravity is about 1"-2" below your naval, just above the pelvic girdle. When these 2 locations a in line in 3 dimensional space, the body is in balance. On a bike they naturally line up when the torso is either above the hips, or laying on the tank. Anyway, what we're doing in this technique is using the natural movement along the 'X' plane to generate the forces required to steer the bike. Which is why it's so a) counterintuitive, B) effective and c) easy once you 'get' it.

 

The primary reason I can attest to this is 15 years of martial arts training. As well as being an engineer, albeit a software specialist. In other words, I write code for a living.

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