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Discussion Starter #1
Okay here is the question.

When trying to manuever slowly a lower CG is better. I think we all agree on that.

So???

1) To get this lower CG I say that one can stand up (on the pegs) which then lowers the CG because now your weight is all being transferred through your feet, thus creating easier manuevering versus staying in the sitting position.

2)Others contend that standing only makes the weight at a higher level thus raising the CG.


I'm in the "1" camp.
 

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I'm with the others.

All you're doing by standing up is raising the bulk of your body, ergo a higher
center of gravity.

But, WTH do I know, I'm on a K12RS :teeth
 

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Discussion Starter #3
I understand that the weight is higher but the bike only realizes the weight where it is placed.....the pegs. Thus lower CG.
 

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kbmwrs said:
I understand that the weight is higher but the bike only realizes the weight where it is placed.....the pegs. Thus lower CG.
And that's all well and good, until you move your head or turn your body in some fashion.
Then all that weight way up high in the new center of gravity affects the machine.

It seems to me. :yesnod:

Or, putting your argument another way, where would you prefer the gas in your bike to be? Up high, or down as close to the pegs as possible ? Once you start tossing it in corners the weight of your load shifts, affecting your center of gravity, affecting the quality of your ride.

Your example may work, but only if the weight is unmovable.
 

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CG is the point of balance in the bike –it doesn’t matter where or how weight is attached, as long as it’s attached. Think of it this way: when sitting, your hips are attached to the seat, the seat is attached to the frame, the frame is attached to the pegs. So how is that really any different than standing, with your hips attached to your legs, your legs attached to your feet, and your feet attached to the pegs?

I believe weight high up makes slow maneuvers more awkward because that weight acts on a longer lever arm to the contact patches, so any lean tends to pull the bike more strongly over. You, the rider thus have to exert greater counter-torque to keep the bike from falling over, making handling more difficult. It doesn’t matter how the weight is attached as long as the lever arm is the same length.

When you stand on the pegs like a dirt rider, you still have a weight up high (the CG is raised), but now _you_ control the weight, so you can take advantage of the long lever arm to increase your control –it takes less lean to achieve the same counter-torque for whatever the bike below you is doing. That’s probably why you feel more control by standing on the pegs.

Standing on the pegs also makes it easier to shift more weight. You can put almost 100% of your weight on one side very quickly. When seated, you have to hang off to get the same effect.

I’m an engineer, but not a _real_ engineer.
 

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Yeah, this question comes up every so often, especially in dirt bike circles. So here's the one true and correct answer:

Standing up on the pegs raises the combined center of gravity of the bike and rider. Yes, it does.

It may "feel" easier to maneuver that way, but that is due to one simple consideration which is often overlooked here: the bike and rider are not a single, rigid body.

Sitting on the seat effectively ties your butt to the bike which limits your movement in relation to the bike. And your main body weight is lower, so the combined CG of bike and rider is lower.

Standing on the pegs moves your weight higher (and thus raises the combined CG), but makes it easier for the bike to move a bit beneath you due to your legs bending and shifting and thus your main body mass moves easier in relation to the bike.

So no real controversy here, just an oversimplification of the forces at work leading to an incorrect conclusion that "feels" right. :)
 

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As a long time dirt bike rider and former MX racer, I can tell you that on tight single track, you'd better be off the seat and on the pegs. Standing puts your weight low on the pegs. Sitting on the seat puts the weight high up on the seat.
 

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JM1200GT said:
Standing puts your weight low on the pegs. Sitting on the seat puts the weight high up on the seat.
And that only works because it allows the bike to move around underneath you. But the total CG is still higher than if you were sitting.

Again, you and the bike are not one, single rigid body here.

Fergie said:
Sorry, still incorrect, even if it "feels" right. :D
 

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Standing on the pegs 'lowers' the COG because your weight is on the pegs? So, that would also be true if you were standing on stilts on the pegs with your body 10 feet above the seat? Yeah, right.
 

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I agree with the few of you who have the right answer :yesnod: . But placing my own opinion here seems futile at best :bash: . So I'll just hold onto my :twocents: .
 

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Once again proving that the GT would handle a hell of a lot better if my ass wasn't parked on the seat.......... :wtf:
 

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In marine terms - if you have a weight on the deck of a ship and you sling it onto a derrick (crane),the moment you pick the weight up it is acting as though it is at the top of the derrick. Therfore the CofG of the vessel rises - SO when the rider stands his body weight moves down to the pegs therfore lowering the CofG.
Dave (lol)
 

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Jeromy said:
I agree with the few of you who have the right answer :yesnod: . But placing my own opinion here seems futile at best :bash: . So I'll just hold onto my :twocents: .
:teeth :rotf: :rotf: :teeth
 

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if you think of it as the center of mass instead of center of gravity it might make more sense.

the mass of your body sits higher moving the the center of mass higher. regardless of where you are standing.
 

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G-DAVE said:
In marine terms - if you have a weight on the deck of a ship and you sling it onto a derrick (crane),the moment you pick the weight up it is acting as though it is at the top of the derrick. Therefore the CofG of the vessel rises
Yes, it rises because you've moved the weight up higher. Just as you do when you stand up.

And again, when the weight is sitting on the deck, it and the ship are tied together as a solid unit. But once you lift it, the weight is free to swing about on its cables, and so the forces act differently than if it was simply lifted to the top of a rigid tower and stuck there.

Standing up moves the combined CG higher, period.

But it also allows you to bend your legs and apply your body mass to the pegs, or to just one peg if you wish.

There is a difference between pure center of gravity of a combined solid mass and the individual forces applied by loosely coupled bodies.

For example, if I stay seated on the bike, and a car hits me from the side, the bike will move sideways. That doesn't change the center of mass of me and the bike, but it does add a sideways force acting on my bike.

Standing up simply means that you, as a flexible body, can apply your force (weight) to a different part of the bike. But the combined body of you and the bike will still have a higher CG.

You simply cannot lower the center of gravity of an object or set of coupled objects by raising it.

Trust me guys, this is correct, regardless of what it may "feel" like to you. :)
 

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GillyWI said:
Once again proving that the GT would handle a hell of a lot better if my ass wasn't parked on the seat.......... :wtf:
True enough, as my GT handles much better with my ass parked on it than it would with yours parked there. :D
 

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+1 for everything Meese posted. I started reading this thread and was thinking of a reply, but Meese beat me to it.

Meese is 100% right. I will back that statement up with years of teaching experience in the physics department of a large university.


Meese said:
True enough, as my GT handles much better with my ass parked on it than it would with yours parked there. :D
Alright, Meese is 99% right. :teeth
 

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Meese said:
And that only works because it allows the bike to move around underneath you. But the total CG is still higher than if you were sitting.

Again, you and the bike are not one, single rigid body here.

Sorry, still incorrect, even if it "feels" right. :D
I'm with Ken here, but I base my opinion only on practical experience, rather than any scholarly approach. I rode a motorcycle (H-D FLHTP) in the course of my job as a police officer for several years. I've been to 80 hours of basic Motor School, 120 hours of Motor Instructor School, through the H-D/Northwestern University program and many hours of refresher training. I also took the Lee Parks Total Control Level 1 class this Spring. I can tell you without hesitation that neither I, nor any other Motor Officer I have ever seen, would consider standing up to maneuver through a slow speed course. I know lots of police riders that are way better than me and have never seen them do it either.

That doesn't mean that police riders are the end all in terms of skill, but we do have the slow speed stuff down pretty good. I'm sure there are differences if you ride in the dirt, but I have taken my H-D in some places that common sense would tell you not to go and never had to stand up to increase my control. Granted, standing up on the floorboards of an H-D FLH would require some maneuvering, but it can be done.

Just my opinion, but based on lots of time spent on my side on the ground and picking up my motor. It's all about balance and stability. I think if you were standing up it would be too easy to get off balance.
 
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