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Discussion Starter #1
High COG = Bad

I thought I'd post this because there was some discussion about a high COG actually being a good thing.

I remember reading an article in Cycle World that explained this. It was a full page long with lots of formulas and technical information, but on the next page was a very simple and easy to understand explanation. Here it is in a nut shell. Stand in front of your bike and mentally draw a line vertically starting at a point where the tires contact the ground. Are you drawing? Good. Now stop the line at the same height as the handlebars. This is your lever arm. Now imagine this lever arm weighs 800 lbs. Now imagine that 795 of those 800 lbs. are 1/2” off the ground. This is a very low COG. Now reach out and grab the handlebars, I mean the top of the lever arm, and jerk it as fast as you can right to left. Are you jerking? I knew that you where. Fast, easy and requires very little effort. You can STOP jerking now.
Now imagine that 795 lbs. is ½” from the top of the lever arm. A very high COG. Now jerk that! A good doctor might be able to pop that back into place.

The point of the article was, all other things being equal; a bike with a lower COG will handle better than a bike with a higher COG.

Now to really stir the pot; when do you think your COG is lower: standing on the pegs or sitting on the seat?
 

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Now to really stir the pot; when do you think your COG is lower: standing on the pegs or sitting on the seat?[/QUOTE]

Standing on the pegs...
 

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Wrencher Extraordinaire
2005 K1200LT
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In the pegs!

Not to burst your bubble but by the same argument on easy to move it. To maneuver you don't move the TOP of the bike (easy in low CG) rather you move the BOTTOM of the bike (easy in high CG). Try it the next time you are out. Hit the bars and see what the bike really does in the corner. You will find the wheels move out from under you to establish the lean angle.:)

That is why a high CG is more maneuverable. It makes the bike more unstable and and the less stability you have to over come the easier it is to maneuver.
 

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Discussion Starter #4
Do three rights equal a left?

At some point in this turn you have to right the beast and sometimes (very quickly) go the other way. A low COG is what makes a bike “flickable”. Try it the next time your out. Go right and left.

Standing on the pegs is correct. I am always impressed by the difference in my KTM when riding on the pegs though a really nasty section.
 

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Now to really stir the pot; when do you think your COG is lower: standing on the pegs or sitting on the seat?
steamboatjohn said:
Standing on the pegs...
Is that because your weight bearing onto the bike has been transferred to the pegs, which are lower?

Following up on that, while the bike's CG may be lower at that point, would it not be fair to say that the rider's CG is higher, making the rider less stable on the bike? :stir: :stir: :stir: :v:
 

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With all of your weight bearing on the pegs, you still do not displace the mass of your tourso....it's a movement and "moment" issue. The theory hold true in aviation geometry regarding weight and balance. It is where the mass is located that determines the COG.

The lower your butt is on the seat, the lower the COG...remember that Gravity is constantly pulling perpendicular to the ground...so if you are standing on the pegs through a corner, gravity is pulling just as hard (albeit harder) on your upper body, and upsetting the intended balance of the motorcycle.

You don't see superbike riders standing on the pegs going through corners in a race, do you ?...they get as low as possible, and sometimes hang their bodies off the side of the bike to "lower" the COG,and apply more traction to the tires of their machine.

...and then there is centrifugal force to deal with, but that's another thread... :bmw:
 

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Discussion Starter #8
Very Good

deputy5211 said:
Is that because your weight bearing onto the bike has been transferred to the pegs, which are lower?

Following up on that, while the bike's CG may be lower at that point, would it not be fair to say that the rider's CG is higher, making the rider less stable on the bike? :stir: :stir: :stir: :v:
Yes, while standing does lower the COG it might feel less stable, but while standing you are taught to squeeze the tank/seat with your legs. This also works while sitting on a street bike. You should feel more “planted” if you squeeze the bike, especially while cornering. Try it.
 

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Discussion Starter #9
They do put weight on the pegs

K1200LTryder said:
With all of your weight bearing on the pegs, you still do not displace the mass of your tourso....it's a movement and "moment" issue. The theory hold true in aviation geometry regarding weight and balance. It is where the mass is located that determines the COG.

The lower your butt is on the seat, the lower the COG...remember that Gravity is constantly pulling perpendicular to the ground...so if you are standing on the pegs through a corner, gravity is pulling just as hard (albeit harder) on your upper body, and upsetting the intended balance of the motorcycle.

You don't see superbike riders standing on the pegs going through corners in a race, do you ?...they get as low as possible, and sometimes hang their bodies off the side of the bike to "lower" the COG,and apply more traction to the tires of their machine.

...and then there is centrifugal force to deal with, but that's another thread... :bmw:
Superbike riders do put weight on the pegs to lower the COG. They weight the outside peg as much as possible.
 

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Oy! With all due respect, this thread is about as useless as a pig in a prom dress. (At least for me that would be "useless". Some of you guys might find a pig quite attractive in a purty pink prom dress. :D ) But I digress...

The fact that the term "flickable" was used in a thread within the LT forum backs me up, IMO. The only thing "flickable" about the LT is the high-beam switch. We are still talking about an 850-pound motorcycle here, right? The LT does amazingly well in the twisties for it's size...but let's not get carried away. Next we'll be hearing all those stories about the guys blowing away all the sportbikes. As if! All that means is that the schmuck on the sportbike couldn't ride. Those stories mean nothing to me in terms of how well the LT can handle the twisties.

Put the same rider on an LT, my GT, and a new Yamaha R1, let him/her do some laps at Laguna Seca and the proof will be in the lap times. The LT will be embarrassing compared to my GT, and my GT will be embarrassing next to the R1.

The bottom line: The LT has an extremely high COG which is "bad" when going slow. Fortunately, this can be overcome with patience and practice. Furthermore, the LT's high COG is also the reason why it allows the rider so much lean angle. If BMW lowered it's COG, it would scrap far too early. I think BMW did a pretty good job at finding a happy medium.



And now for the quiz-of-the-day: If a higher COG is BAD, why did Kawasaki RAISE the COG on their newest ZX-6R?
 

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Funny, I don't have any problem going from right to left or left to right in the twisties at speed on the LT.
 

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Steve_R said:
Funny, I don't have any problem going from right to left or left to right in the twisties at speed on the LT.
Is that why you were a disappearing speck in my mirrors on the Blue Ridge Parkway? Ya see Steve . . . it's all relative. Your "at speed" and my "at speed" are two different terms. Just as "a high COG" is a relative term.
 

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Absolutely true. And I would never push my LT like you did yours or the GT for that matter. It IS MY RIDE. :)
 

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Discussion Starter #16
The fact that the term "flickable" was used in a thread within the LT forum backs me up, IMO. The only thing "flickable" about the LT is the high-beam switch.

I believe that was my point.
 

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so does shorter rake raise the COG or lower the COG, what about forward weight distribution, or forward controls, big tire and little tire,...what about this grasshopper; if a 1200lb horse can carry 33.333percent or 400lbs...does he handle differently when a 225lb man changes from a 30lb saddle to a 45lb saddle ? :rolleyes: ( i might should not have posted this). :( :eek:
 

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...and just how long would it take a dog screwing a pail full of snowballs to melt it... :histerica
 
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