Hanging off on cruisers and "non" sport bikes?

[Thundurburd]

Originally Posted by Easy Rider

Are you trying to tell us that the center of gravity does not change no matter where the rider's body is located or how much the bike is leaned over ??

When the bike is balanced the combined cg including both rider and bike will not change without external forces such as steering input, but the relative position of each can be changed. If the rider leans left he does so by slightly pushing on the bike causing it to lean right, and the distance moved by each is dependent on the weight of the bike. Heavier bikes will lean less in other words.

For example, if when going around a curve you start dragging the pegs, you can lift them by leaning into the turn which results in the bike leaning the other way (opposite the turn) and straightens up the bike. This actually is an important thing to know IMO.

[Clint]

Originally Posted by Thundurburd

When the bike is balanced the combined cg including both rider and bike will not change...

Yeah, that's what I'm saying. Relative to the contact patches, the CG doesn't move.

[Easy Rider]

Originally Posted by Clint

Yeah, that's what I'm saying. Relative to the contact patches, the CG doesn't move.

Listen, I don't want to get in a pissing contest here but that is just simply not true.

It is center of mass...... and as the rider's body leans left and/or the bike leans left the center of mass moves to the left and gets closer to the ground.....relative to the contact patch and relative to anything else that is not attached to the bike or rider.

This shift in the position of the center of mass changes the angular forces applied to the contact patch. That is not the only thing that affects the forces applied to the contact patch but it IS one of the things.

How can you look at a race rider going around a curve with his knee on the pavement and the bike layed over at more than a 45 degree angle and try to tell me that the combined center of mass (gravity) is in the same place, relative to the contact patch, as it is when he is upright, flying down the straights ?? It just ain't so.

[Thundurburd]

Originally Posted by Easy Rider

How can you look at a race rider going around a curve with his knee on the pavement and the bike layed over at more than a 45 degree angle and try to tell me that the combined center of mass (gravity) is in the same place, relative to the contact patch, as it is when he is upright, flying down the straights ?? It just ain't so.

With no external force applied the rider cannot change the location of the combined cg by simply leaning to one side because the bike will lean the other way. What you're talking about with a racer hanging off to the side of a bike has been accomplished not only by the rider hanging off (leaning) but also with the appropriate steering inputs too.

Yes, the combined cg has changed, but not from leaning.

[Clint]

Originally Posted by Easy Rider

How can you look at a race rider going around a curve with his knee on the pavement and the bike layed over at more than a 45 degree angle and try to tell me that the combined center of mass (gravity) is in the same place, relative to the contact patch, as it is when he is upright, flying down the straights ?? It just ain't so.

That's not what either of us said, and the fact that what you're describing is so obviously incorrect was your first clue to that fact. Give us a little credit already.

Hopefully T-burd has cleared it up for you. If not, here's my attempt: Two identical riders, all other things being equal, will not move the CG of the rider/bike system simply by shifting his weight to the side. Pendulum theory tells us that a CG at a given speed and rotational velocity will remain constant.

[leonidas]

Originally Posted by Thundurburd

When the bike is balanced the combined cg including both rider and bike will not change without external forces such as steering input, but the relative position of each can be changed. If the rider leans left he does so by slightly pushing on the bike causing it to lean right, and the distance moved by each is dependent on the weight of the bike. Heavier bikes will lean less in other words.

For example, if when going around a curve you start dragging the pegs, you can lift them by leaning into the turn which results in the bike leaning the other way (opposite the turn) and straightens up the bike. This actually is an important thing to know IMO.

Well said Mr. Burd.
After learning what is written below, and practicing it every chance I got,
my riding skills got way better, even tho I though I was pretty good
before working on countersteering.
The following is some very important info that I think all riders should
know and practice. This was written by a member of another Motorcycle board I've been a member of for several years. A smart man and a very
good rider. I hope this is seen by many folks here.

"Countersteering - Those that know me know this is something I preach all the time and to everyone I meet on a bike. You can ride without knowing you're countersteering but you can't ride without countersteering. It's a fact, just ask Wilbur Wright (google), any two wheeled thing must be countersteered(notice the lack of quotation marks), or google "Keith code, BS bike".
Some remember it by thinking "press the side of the bar forward in the direction you want to turn". If you want to turn right you press the right side of the bar forward as needed. I myself like to think, "if you want to go right, turn left". Either one does the same thing but I like knowing that pushing, pulling, pressing, yanking, shoving, kicking(ya never know), basically turning that bar in the opposite direction that I need to go, anyway I can, will get me where I need to go. The bar doesn't turn when you try to move it/apply pressure (minutely it does but that's advanced stuff), instead the bike leans. Apply a little pressure and it leans slowly, apply a lot and it moves quickly. It continues to lean more as long as pressure is being applied. When you stop applying pressure to the bar it holds there(if you're leaned way over you'll actually be holding the weight/bull%%%% tech word/gravity of the bike from falling over with your hands). To straighten back up you apply pressure to the bar again as needed.
I like practicing on the straight away. (directions are written for driving on the right side of the road(not the wrong)

Lesson 1: Find a wide road with no traffic and a good long straight away. Ride at a speed your comfortable with and relax your hands on the grips, ahhhhh, breathe. With the bike riding straight and next to the yellow line apply a very little pressure, very little, to the bars as if you were trying to turn left. When the bike starts to move to the right stop increasing pressure and let it slowly move to the center of your lane. When you get to the center of the lane release pressure and apply "right turn" pressure as needed to stop bike from moving to the right. You just countersteered a motorcycle. Simple as that.

Get used to moving back and forth in your lane. You'll notice the more force used the quicker things happen. Depending on how sensitive you are to feeling things you'll feel the weight of the bike switch between your hands as you're playing.
You're actually turning on a straight away. Practice it all the time. Once you can turn on a straight away and put that bike wherever you want it at anytime, almost instantly. Doing the same in a corner isn't that hard.

Practice, Practice, Practice"

[Easy Rider]

Originally Posted by Thundurburd

Yes, the combined cg has changed

Originally Posted by Clint

Hopefully T-burd has cleared it up for you.

Seems pretty clear to me.

[Clint]

LMAO! Nice selective copy. Did you really stop reading the sentence at that point?

[Rickster]

Originally Posted by Clint

I really hate contradicting Rick. He's such a level-headed guy that it makes me squirm inside to do so.

Level-headed,,,,,,,,,,,,,,,right, that's me, I think what he meant to say is he doesn't want to contradict me because he has been reading that thread where we all have been posting pictures of all the guns we own.

[Clint]

Well, flat-headed after that last haircut anyway.

[Easy Rider]

Originally Posted by Clint

LMAO! Nice selective copy. Did you really stop reading the sentence at that point?

Same thing you did with his previous post.
Shoe.....other foot.....pinch.

[Rickster]

Originally Posted by Clint

Well, flat-headed after that last haircut anyway.

That reminds me, I need to get to the barber.

I thought about what you said, and I hate to admit it (to you) but it does make sense, if you are going around the same turn at the same speed every time it wouldn't matter if the bike were straight up and down, or leaned over at a 45* angle, the G forces trying to push the tires sideways would be the same.
So I guess the hanging off only helps if you want to take the turn at a faster speed.
I was wa,,,,,wa,,,,wa,,,,,,,war,,,,war,,,wron,,,,,,,,,,, ,,,,,,,,,wrong.

[Clint]

I understand how painful that was, and I'm truly sorry.

[Wyldesoul]

Easyrider... That is completely not the question relevant. Rickster had stated that leaning changes the forces applied to the contact patch in a curve, which is not true.

You take the same bike, same rider, same speed and the same curve, it will ALWAYS have the same CG relative to the contact patch, and therefore the same forces.

Leaning your body merely allows the bike to be more vertical, because you're spreading the mass out over a larger space. When you pull yourself tight to the tank, your mass is closer to the bike's, and so the bike's lean angle is closer to the angle of the CG to the contact patch. When you hang yourself off to the right, you shift the center of mass of the bike/rider to the right of the bike. That center of mass will be in the exact same spot as the center of mass in the last run, but since the center of mass is to the right of the bike, logically, the bike will be to the left of the center of mass, and so in a right turn, the bike will lean less.
With a heavier bike, your mass is less of the percentage of the bike's mass, and so you hanging off to the side won't shift the bike/rider center of mass as much, and so your hanging will have a less pronounced effect.

Of course the CG will be different in a straight than a curve, of course it matters how sharp the curve is or how fast the bike is or how heavy the bike or rider is... All those variables change the CG. However, the CG CANNOT be changed merely by hanging, that merely changes the position of the components of the CG.

Hanging does 2 things, and 2 things alone. Keeps you from dragging parts on the bike, and keeps the contact patch of the tire in the tread.

However, because those 2 factors are what determines the max lean angle of a bike, hanging off will allow the relative "lean" of the CG to exceed the max lean of the bike, which is it's real use.


Edit: Er... Sorry if I'm beating a dead horse. I admit I hadn't fully read the post that Rickster had just did. I do hope I did a bit of good explaining the concept, though.

[Easy Rider]

Originally Posted by Wyldesoul

Of course the CG will be different in a straight than a curve,
All those variables change the CG.

Yes. Of course it does.

I give up.

[Easy Rider]

Originally Posted by Rickster

........it wouldn't matter if the bike were straight up and down, or leaned over at a 45* angle, the G forces trying to push the tires sideways would be the same.

Well you see, that's not exactly true either because you aren't taking force VECTORS into account. The total force is likely to be about the same but it is applied in a different plane or vector.

If you have the proper lean, that is the proper placement of the center of mass, the forces will be applied to the contact patch in a way that will maximize the traction.

If the center of mass isn't leaned over far enough, part of those forces tries to push the bike and rider OVER and that portion of the force is NOT applied to the contact patch.

Too much lean and you low side. Not enough and you high side or run off the outside of the curve...... or both.

[m50Joe]

[Clint]

Originally Posted by Easy Rider

Well you see, that's not exactly true either because you aren't taking force VECTORS into account. The total force is likely to be about the same but it is applied in a different plane or vector.

If you have the proper lean, that is the proper placement of the center of mass, the forces will be applied to the contact patch in a way that will maximize the traction.

If the center of mass isn't leaned over far enough, part of those forces tries to push the bike and rider OVER and that portion of the force is NOT applied to the contact patch.

Too much lean and you low side. Not enough and you high side or run off the outside of the curve...... or both.

Umm... no. You have weight, and you have inertia, and in the simple situation we're working with, they're all that are relevant. Since the CG doesn't move, the forces on the tires don't change either. However, the shape of the tire can change the contact patch area for a given lean angle. Sportbike tires actually increase area as lean is increased.

Apparently you still don't believe the rest of us that shifting body weight doesn't change the dynamics of the system from the tire's perspective. We can't really have a conversation until you do.

[GeorgiaRoller]

So what's a person to do who doesn't really care about the mathmatical breakdown of G-Force's, center of gravity, vectors, planes, pendulum theories or just argueing for the sake of argueing?......................................... ..........................................Oh yeah!They go out and ride for fun and leave all the techno-babble to the engineering types back home on their computers!

Sometimes not being smart can be a good thing!

[Clint]

It's not about smart or dumb, but an interest in learning. I'm a lifetime student who only knows enough to truly understand how much I don't know.

Oh, and we're currently receiving another 6-8" on top of a nice ice storm. Should I go riding?

At the moment I'm studying several programming languages and Microsoft development platforms in preparation for the most promising (read: only) job interview I've had to date, which happens in two hours. Wish me luck.