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 Turning causes leaning?
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trailrider
Ex-Member

Posted - 06/30/2010 :  10:55 AM                       Like
Mr. D says turning causes leaning. Perhaps, but I can't picture that. What I can picture is that steering causes leaning. Steer to the left, bike leans right, and the reverse.

I use the word turning to mean a curving path of the bike and the word steering to mean changing the direction of the front wheel reletive to the frame.

So when you say that turning causes leaning do you mean the same thing as steering causes leaning?

James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/30/2010 :  11:54 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Okay, you posted this in the contrary opinions area so I'll treat it like you find fault with my own opinions.

I have said that leaning does not cause turning, turning causes leaning. You find fault with that.

In this context, the differentiation is between direction traveled as opposed to lean angle.


But I wonder if you are simply wordsmithing instead of dealing with the concepts. You seem to want to differentiate between turning and steering.

Fine, but first, let's get the FACTS agreed with.

You, I assume, agree that centrifugal force (or, centripetal force) is what causes leaning and that leaning does NOT cause centrifugal force.

So, would you be happier if I said that changing direction traveled changes centrifugal force?

Steering is an activity. If your bike is riding in a straight line, most people would argue that you are steering in a straight line. In fact, no steering is necessary - if the bike is moving in a straight line and there are no steering inputs, the bike continues in a straight line. And, of course, there is no lean angle.

If your bike is moving in a clockwise direction, your bike is leaning to the right - the result of centrifugal force. There is no question that you are TURNING. However, as Scott R Nelson has often observed, some bikes in certain situations have 'neutral steering' - meaning that NO steering input is needed to maintain that turn. Still turning, not steering, still leaning - right? Still want to claim that steering causes leaning?

If you are trying to differentiate between steering and counter-steering, that's a different argument.


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Fajita Dave
Male Starting Member
3 Posts


Kutassy, Virginia
USA

Suzuki

GSX-R600

Posted - 07/01/2010 :  4:17 PM
I'm new to this forum so I'm not sure if there is something else that was conversed about this "turning causes leaning" topic. Anyway, here are my thoughts on this.

Taking the phrase "turning causes leaning" literally would mean that the act of your motorcycle turning right causes the motorcycle to lean right which is completely false. The motorcycle leaning right is what is making it turn right. As the motorcycle is leaning right the earths gravity is trying to pull it to the ground from its center of gravity. In order for the motorcycle to continue leaning without actually falling it would need to turn which creates G forces that fight the earths gravity and keep the motorcycle from just falling over. So it should be "leaning causes turning."

If the tires have 100% traction this is also what sets the lean angle. If the motorcycle is leaned further then gravity has more leverage to pull it down by its CG. Thus the motorcycle needs to turn sharper otherwise it will fall to the ground. This is proven that a 45 degree lean angle on any motorcycle from its CG is exactly 1G of horizontal cornering force. That is simply the physics of it anyway.

The earths gravity and cornering G forces are the things that make a motorcycles geometry work. Once a motorcycle is leaned into a corner the front tire falls into the turn because of how the motorcycles geometry is designed. The front tire will follow the radius of the turn based on your lean angle (if it didn't at any point that would mean the front tire is sliding). How the motorcycle holds its lean angle is based on its geometry. Some motorcycles like to stand up after being leaned over, some like to lean into the corner, some are neutral and hold whatever lean angle you put them in. Tire profiles have have a heavy effect on this as well. Counter-steering leans the motorcycle simply because when you turn the handlebars left, weight is transfered to the right which makes the motorcycle lean right.

I hope that helps clear things up.

Edited by - Fajita Dave on 07/01/2010 4:25 PM
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/01/2010 :  4:27 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Not only does it NOT clear things up, it is patently wrong.

I suggest that you start reading some of the many discussions on this site about counter-steering and leaning versus turning. There is a search function that works quite well.

Leaning is the RESULT of centrifugal force, not the cause of it. Centrifugal force results from an object moving in anything other than a straight line. And because a vehicle changes direction as a result of steering input, it follows that leaning results from a change of direction of travel.

We here on this site are not uneducated as to the physics involved.

While it is true that we welcome discussion of opinions that may differ from ours, it is also true that when statements are made in declarative form such as: "The motorcycle leaning right is what is making it turn right.", as you just did - implying them to be facts - you should expect to be challenged to defend such statements. Or, to man up to the fact that you are wrong.

As to your popularly held opinion that leaning is why bikes turn ... I suggest that there are only TWO things you can control on a motorcycle that is moving faster than about 10 mph: direction of travel and speed. Have you ever seen a 'lean' control on a motorcycle?
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trailrider
Ex-Member

Posted - 07/01/2010 :  6:45 PM
quote:
Originally posted by James R. Davis

Okay, you posted this in the contrary opinions area so I'll treat it like you find fault with my own opinions.
I posted here because it seemed like the safe place to post. I don't know if I disagree because I don't understand.
quote:
I have said that leaning does not cause turning, turning causes leaning. You find fault with that.
I don't understand that. which is why I brought it up.
quote:
In this context, the differentiation is between direction traveled as opposed to lean angle.

But I wonder if you are simply wordsmithing instead of dealing with the concepts. You seem to want to differentiate between turning and steering.
I wouldn't start a thread for playing word games. It's helpful to me to have one word for changing the steering angle and another for the curved path.
quote:


Fine, but first, let's get the FACTS agreed with.

You, I assume, agree that centrifugal force (or, centripetal force) is what causes leaning and that leaning does NOT cause centrifugal force.
What causes the centrifugal force?
quote:

So, would you be happier if I said that changing direction traveled changes centrifugal force?
Where can I read up on that because I don't understand what you are describing. What causes the change of direction? There is a chain of causes and I don't have them in the right order or there's someting missing from my list.
quote:


Steering is an activity. If your bike is riding in a straight line, most people would argue that you are steering in a straight line. In fact, no steering is necessary - if the bike is moving in a straight line and there are no steering inputs, the bike continues in a straight line. And, of course, there is no lean angle.
My impression from riding the bike is that the bike is always changing lean angle. On a straight path it would be rocking to one side or the other of 0 degrees, may be just fractions of a degree, so if you studed the straight path from above you'd see subtle S curves down the straight path.
quote:


If your bike is moving in a clockwise direction, your bike is leaning to the right - the result of centrifugal force. There is no question that you are TURNING.
Again, what causes the centrifugal force?
quote:
However, as Scott R Nelson has often observed, some bikes in certain situations have 'neutral steering' - meaning that NO steering input is needed to maintain that turn. Still turning, not steering, still leaning - right? Still want to claim that steering causes leaning?
My impression is the rake and trail are such that when the bike is leaning the front wheel wants to turn in that direction. I've noticed when I'm riding if I steer the wheel to one side the bike wants to lean to the opposite side. That's how if feels. If the bike accelerates or decelerates during a turn it will try to change lean angle and I can try to hold the lean angle by steering inputs. That's the way it feels.
quote:
If you are trying to differentiate between steering and counter-steering, that's a different argument.
And there I'm confused again. The way it feels, steering always has the same effect, to make the bike want to lean in the opposite direction I'm steering the front wheel. May be that's not right but that's the way it feels. The way it feels there's no steering or counter steering, just steering.

May be the part I'm not understanding is the centrifigal force and what causes that.
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/01/2010 :  7:07 PM Follow poster on Twitter  Join poster on Facebook as Friend  
Whenever your motorcycle is traveling in other than a straight line it is traveling in a curve which is an arc (part of a circle).

An object that is moving has momentum. Inertial effects are a function of speed (squared) and radius of the curve traveled.

So, there are two concepts that you need to get your arms around: centrifugal force and how strong that force is.

Any object that is not traveling in a straight line is experiencing centrifugal force. That object, because of inertial effects, wants to continue traveling in a straight line but your tires are changing its direction. Centrifugal force is what you feel because the moving object (you and your bike) are trying NOT to change direction.

How strong is that force? It is a function of the square of your speed and the radius of the turn you are making.

Why is that important? Because at very low speeds (less than about 10 mph), centrifugal force is essentially trivial and that is why you must STEER instead of COUNTER-STEER at higher speeds.

quote:
The way it feels, steering always has the same effect, to make the bike want to lean in the opposite direction I'm steering the front wheel.

And now you know that's not true. Turn the front wheel to the left at 5 mph and the bike will turn to the left (and fall in that direction, too). Turn it to the left at 20 mph and the bike will turn to the right (and 'fall' to the right as well) ... Because centrifugal force is stronger than gravity at such speeds.
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Fajita Dave
Male Starting Member
3 Posts


Kutassy, Virginia
USA

Suzuki

GSX-R600

Posted - 07/01/2010 :  10:13 PM
I have no problem what so ever admitting that I'm wrong. You can't learn anything if you don't take into consideration the words from others. I definitely do not have a degree in physics either.

quote:
Originally posted by James R. Davis


Leaning is the RESULT of centrifugal force, not the cause of it. Centrifugal force results from an object moving in anything other than a straight line. And because a vehicle changes direction as a result of steering input, it follows that leaning results from a change of direction of travel.



I 100% agree with that. I guess this is where I went wrong with the mindset here. I'm thinking in terms of what causes the motorcycle to turn and not how you make it lean.

So let me make sure I have this straightened out. At speed if you turn the handlebars it makes the motorcycle lean (counter-steering). A leaning motorcycle needs the centrifugal force created by its turning radius otherwise it will lean lower and/or fall. The motorcycle turns because while leaned over the front tire is pointing in the direction of the corner. When the front tire is turned further into the corner it wants to follow a tighter radius which results in more centrifugal force causing the bike to stand up.

In my first post I concluded that the motorcycle NEEDS to turn while at any lean angle otherwise it will simply fall but by turning the handlebars you change the lean angle.

Please correct me anytime that I'm wrong. I never take offence to it and would rather get a better understanding of things.
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/01/2010 :  11:32 PM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
A leaning motorcycle needs the centrifugal force created by its turning radius otherwise it will lean lower and/or fall.

While that sounds right, it is only true at low speeds.

When you are making a tight turn in a parking lot at, say, 5 mph, and the bike feels like it is going to fall down, you increase speed and centrifugal force stands the bike taller to prevent its falling.

At speeds higher than about 10 mph, if you are making a turn and it feels like it is going to fall down, you must SLOW DOWN in order to get the bike to stand taller and not fall down. HONEST!

When you enter a turn 'too hot' (meaning too fast) your pegs scrape. The faster you enter that same turn, the greater will be its lean angle. Obviously, then, the SLOWER you make that turn, the less lean the bike will have.

When you are riding at counter-steering speeds (above about 10 mph), centrifugal force makes the bike lean more, not less, as you add speed.

The way to imagine this in layman's terms is to think of the centrifugal force affecting the contact patch instead of your head. The greater the centrifugal force, the harder it is trying to push the contact patch away from the center of the turn.

Or, you can imagine that since the bike is leaning into the turn, your head is closer to the center of the turn than are your tire contact patches. You know that the contact patches MUST, therefore, be traveling faster than your head is in order for your body to stay intact. Thus, the contact patches MUST be feeling greater centrifugal force than does your head.

These are only suggested ways to think of what's happening that might make it easier to appreciate that the faster you ride your bike in a turn, the greater will be its lean angle.

quote:
In my first post I concluded that the motorcycle NEEDS to turn while at any lean angle otherwise it will simply fall but by turning the handlebars you change the lean angle.


Let's re-group. First, let's agree that you do not need ANY lean angle to make a turn. Cars do it all the time, right?

What determines your direction of travel is the direction your front contact patch is pointing (discounting slip angle) - ALWAYS - and has nothing whatever to do with lean angle.

Because your motorcycle is a single track device, when you turn it leans. That is not at all the same as saying that if your bike leans, it is turning. You can drive in a perfectly straight line with a strong cross wind and your bike will be leaning but not turning, right?

If you are riding in a circle at speeds greater than about 10 mph and your bike is leaned over at, say, 20 degrees, and you tighten the radius, the lean angle will get larger, not smaller. If instead if tightening the radius you simply increased speed, the bike's lean angle will also get larger, not smaller. Since in both cases you are increasing centrifugal force, it should be obvious that increasing centrifugal force while riding at counter-steering speeds INCREASES the lean angle.

Finally, let's agree that the ONLY way you can make your radius tighter if you maintain speed is to TRY TO turn AWAY from the center of the turn at these speeds (because counter-steering is NOT OPTIONAL). Turning away from the center of the circle you are riding causes the bike to lean toward the inside of the turn and is quickly followed by the bike's front wheel actually turning toward the inside of the turn.



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trailrider
Ex-Member

Posted - 07/08/2010 :  8:36 PM
quote:
You, I assume, agree that centrifugal force (or, centripetal force) is what causes leaning and that leaning does NOT cause centrifugal force.
Centrifugal force tries to lean the bike to the outside of the turn. The controls are used to lean the bike the opposite way, against the centrifugal force.
quote:
So, would you be happier if I said that changing direction traveled changes centrifugal force?
I agree with that.
quote:
If your bike is riding in a straight line, most people would argue that you are steering in a straight line.
I would prefer to say there can be a straight path but a straigt line is impossible because the bike is always changing lean angle and that should result in a straight path made of subtly curved lines.
quote:
In fact, no steering is necessary - if the bike is moving in a straight line and there are no steering inputs,
My intuition is, at good speeds the bike is steering itself, self correcting because of the rake and trail of the front forks. The reason this makes sense to me is because if the front forks were locked solid pointing straight ahead the bike would fall down with the slightest deflection.
quote:
the bike continues in a straight line. And, of course, there is no lean angle.
See above. I believe there is no "straight line" and the lean angle is always changing, even if only by small fractions of a degree on either side of zero.
quote:
If you are trying to differentiate between steering and counter-steering, that's a different argument.
I don't think that differentiation exists. My perception is steering always has the same effect, the bike always leans, or tries to lean, in the opposite direction of the steering angle change.
quote:
Leaning is the RESULT of centrifugal force, not the cause of it.
My intuition is centrifugal force is trying to cause is a lean to the outside and the rider uses the controls to lean the bike to the inside of the turn so the bike turns instead of falling to the outside.
quote:
Have you ever seen a 'lean' control on a motorcycle?
Yes, several. Throttle, steering, brakes and even body weight are used to influence lean angle of the bike.
quote:
at very low speeds (less than about 10 mph), centrifugal force is essentially trivial and that is why you must STEER instead of COUNTER-STEER at higher speeds.
It seems to me centrifugal force is never trivial. Gravity, friction, and centrifugal force must be measurable forces at all times or it's impossible to maneuver the bike.
quote:
Turn the front wheel to the left at 5 mph and the bike will turn to the left (and fall in that direction, too).
My perception is the bike must always be leaning in the direction I'm intending to turn either before the wheel is steered in that direction or simultaneous to the lean in that direction otherwise the bike is going to fall over to the outside, even at slow speed.
quote:
Turn it to the left at 20 mph and the bike will turn to the right (and 'fall' to the right as well)
My perception is steering the front to the left only leans the bike to the opposite side. At slow speeds and tighter turns the bike doesn't begin turning in the desired direction until the lean is stabilized by turning the wheel back in the direction of the turn. I've noticed situations at higher speeds where I lean the bike by steering and when I ease off it doesn't seem like the front wheel steered back in the direction of the turn. One explanation for this in some turns is perhaps the rear tire is sliping just enough so that there is a curving path without positive steering angle in the direction of the turn. The visible example of that is the supermoto racers drifting through turns.
quote:
At speeds higher than about 10 mph, if you are making a turn and it feels like it is going to fall down, you must SLOW DOWN in order to get the bike to stand taller and not fall down. HONEST!
In my experience if I decelerate in a turn lean angle increases unless I compensate by increasing steering angle in the direction of the turn. Another option is to compensate by leaning body weight more in the direction of the turn but it has limited effect compared to steering.
quote:
When you are riding at counter-steering speeds (above about 10 mph), centrifugal force makes the bike lean more, not less, as you add speed.
My perception is centrifugal force wants to lean the bike to the outside of the turn. That is countered with the controls, mosty by using steering to lean the bike in the opposite direction that centrifugal force is trying to cause.
quote:
Let's re-group. First, let's agree that you do not need ANY lean angle to make a turn. Cars do it all the time, right?
As mentioned above, I can't turn the bike at any speed unless it is leaning in the direction of the turn. Cars lean in turns the same as bikes. The difference is they have 4 wheels so they can turn while leaning to the outside of the turn, unlike motorcycles.
quote:
What determines your direction of travel is the direction your front contact patch is pointing (discounting slip angle) - ALWAYS - and has nothing whatever to do with lean angle.
For an instant that might be true but if the lean angle is not correct for the speed and desire path the bike will not continue on the intended path. The path will get tighter or open up or the bike will fall.
quote:
Because your motorcycle is a single track device, when you turn it leans.
I would prefer to say, when I lean the bike with the controls and maintain a lean angle while moving the bike will turn. The controls cause the lean, maintaining the lean angle, mostly with steering and throttle causes the turn.
quote:
You can drive in a perfectly straight line with a strong cross wind and your bike will be leaning but not turning, right?
Agreed but doesn't there still have to be a steering adjustment to maintain the straight path? I don't get to ride in powerful cross winds very often though I've been in a few. At this moment I can't recall how I steered to maintain the straight path. Help me out with that.
quote:
If you are riding in a circle at speeds greater than about 10 mph and your bike is leaned over at, say, 20 degrees, and you tighten the radius, the lean angle will get larger, not smaller.
And my perception is I will increase lean angle by reducing speed or steering away for the direction of the turn then maintain that new lean angle with steering and throttle resulting in a tighter radius turn.
quote:
Finally, let's agree that the ONLY way you can make your radius tighter if you maintain speed is to TRY TO turn AWAY from the center of the turn at these speeds (because counter-steering is NOT OPTIONAL). Turning away from the center of the circle you are riding causes the bike to lean toward the inside of the turn and is quickly followed by the bike's front wheel actually turning toward the inside of the turn.
If I can't increase lean angle by decelerating then there's going to be a steering change to the outside to do it. I agree. Even so to stabilize that lean angle the wheel will have to be pointed back in the direction of the turn.

So all of the above is not meant to start an argument. It's my best understanding. Even if "turning causes leaning" is correct I don't understand it. I still don't understand it even after a considerable amount of thought and observing what seems to be happening in practice, on the bike.

I'm enjoying this exchange and not meaning to be argumentative. There is no debating the physics, only understanding it. I'm sure I don't undertand it all.
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/08/2010 :  9:24 PM Follow poster on Twitter  Join poster on Facebook as Friend  
When you duck reality by refusing to agree that you only can control speed and direction of travel when riding at counter-steering speeds, and insist, instead, that there is a 'lean control' that consists of steering and speed control, then there is some question in my mind about your sincerity here.

This entire thread is about cause and effect. *You* can cause a change of direction of travel, or a change of speed. As a result of those effects of your efforts, the bike's lean angle will change. That's an effect.

I defy you to change the lean angle without changing the direction of travel or its speed. I do that with confidence because there is no lean angle control. (By 'lean angle', of course, we are speaking about the lean angle of the COMBINED bike and rider.)

When you categorically deny that there is any difference between the behavior of your bike while turning at sub-counter-steering speeds and while turning at counter-steering speeds, then there is some question in my mind about your sincerity here.

I defy you to turn your handlebars to the left while moving at 5 mph and cause your bike (and body) to lean toward the right. Do it at 20 mph and you cannot avoid the lean to the right.

I defy you to explain how it is that you can ride on the exact same path through a turn at 20 MPH, then at 40 mph, and then explain to me that increased speed in combination with centrifugal force decreases the lean angle. Or, that decreased speed in combination with centrifugal force increases lean angle. NO NEW STEERING INPUT REQUIRED, yet the results are always the same - at counter-steering speeds, braking stands your bike up. You don't have to argue that at 5 mph while driving in a curve, if you slow down your bike leans more or that you can 'save' a falling bike in a curve at 5 mph by increasing your speed as we all know that is true.

So here is a simple concept for you to play with ... You are riding in a straight line at 50 mph and have removed your left hand from the bars and lifted your fingers from the right grip leaving only the palm of your right hand touching the grip. Now press forward gently with your right hand. What happens to your direction of travel? To your lean angle? How did you input that new steering input you argued about to start you moving to the right instead of to the left?

And while you are at it ... since you are so strongly of the opinion that centrifugal force pushes you toward the outside of your turn, how do you explain that your bike (and body) actually lean INTO the turn while you are turning?
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CaptCrash
Male Advanced Member
744 Posts
[Mentor]


Nampa, ID
USA

Honda

Phantom

Posted - 07/08/2010 :  11:03 PM
Not looking to muddy the waters here but my FAV video of a bike trying to do what it wants to at speed (run straight and true) is this one of Randy Mamola:

http://www.youtube.com/watch?v=0vzHO9Evb1g

Here's another beaut:

http://www.youtube.com/watch?v=BGKhkO-SsDk

And another:

http://www.youtube.com/watch?v=vkYKFZEeEE4

These sorts of videos help me visualize and realize that at speed the bike really DOES want to go in a straight line until acted upon by the rider.
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/09/2010 :  8:48 AM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
quote:
Let's re-group. First, let's agree that you do not need ANY lean angle to make a turn. Cars do it all the time, right?


As mentioned above, I can't turn the bike at any speed unless it is leaning in the direction of the turn. Cars lean in turns the same as bikes. The difference is they have 4 wheels so they can turn while leaning to the outside of the turn, unlike motorcycles.


My declaration was badly stated, extreme and misleading. I was referring to leaning INTO a turn when I mentioned a car. I was also thinking of JUST the bike, not the combined bike and rider. (When a rider hangs off he can cause the bike to ride vertically when in a turn.) It is also possible that given the proper turn radius and speed (the cross-over speed between steering and counter-steering) that the bike would be vertical during that turn.

In any event, it was not consistent with the rest of the argument I used. I apologize.
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rbperrie
Male Starting Member
9 Posts


Downingtown, Pennsylvania
USA

Harley-Davidson

Low Rider

Posted - 07/09/2010 :  10:48 AM
I will take a crack at trying to explain the physics of this discussion as simply as possible as the OP seems to be trying to understand the underlying physics. In reading through these posts there is a lot of discussion of the relationship of turning and leaning. James is correct is what he is saying but the OP is not understanding so let me take a different path to say the same thing as James. I do not mean to speak for James at all and indeed he may disagree with my approach but in the end we are getting to the same physics which can not change, so here goes.
First, there is no DIRECT relationship between turning and leaning, only secondary. What do I mean? If you sit on the bike at a standstill holding the bars perfectly straight and pick up your feet. With no steering input whatsoever eventually the bike will start to lean and fall over. Indeed, if the bike is not moving you can turn the bars all you want, the bike will still fall over. So the point here is there is not a direct "cause and effect" relationship of turning and leaning. In this scenario the bike will lean no matter how much or how little turning you do. So what does cause leaning? In our stationary bike example it is simply a result of not keeping your weight "balanced" on the bike. More specifically it is keeping the center of your weight directly over the track line of your wheels. If your weight shifts to one side or the other of that track line you will start the lean process in that direction of the offset.
OK, now let's look at what turning does on the bike. We've already seen that at zero speed it does nothing. Now at speed we have to consider Mr. Newton's laws of motion, specifically in this case, an object in motion stays in motion unless acted upon by an outside force. Centrifugal force is the force that tries to keep an object going in the same direction. So we are now at speed traveling in a straight line. To the OP point, yes, in fact we are making little changes in steering to indeed keep our center of weight (CG if I may)over the track line yet for the sake of simplicity of this discussion we will assume that is not taking place. Also we are assuming for simplicity that the CG of the rider/bike does not change. Yes, we see racers shifting their weight and dragging their knees to lower their CG to change the lean angle of the bike but that is for a later discussion. Back to our staight line, moving forward, "balanced" CG and we then turn/steer to the left. The input causes the bike to go left yet your CG will continue to go straight. So now bike has gone left your CG is going straight and your CG is no longer "balanced" over the track line so just as in the stationary example when your CG is no longer perfectly "balanced" the bike will lean and in this case it will lean to the right even though our steering input was to the left. This is where the term counter-steering comes from, to make a right turn we started the process but steering to the left or a "counter-steer". Now, if we keep the steering input to the left you would simply continue your lean to the right and fall over. So we initiate the lean process with a counter-steer in the opposite direction. So now how do we stop the bike from continuing its lean to the right? Now we do indeed steer to the right because this will cause the centrifugal force that will stop the lean motion. Again, to the OP, yes, this is the force you feel pushing you to the outside of the turn. The amount of centrifugal force is determined by your speed and the radius of your turn.

Hope this helps....
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James R. Davis
Male Administrator
17286 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 07/09/2010 :  12:05 PM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
Now, if we keep the steering input to the left you would simply continue your lean to the right and fall over. So we initiate the lean process with a counter-steer in the opposite direction. So now how do we stop the bike from continuing its lean to the right? Now we do indeed steer to the right because this will cause the centrifugal force that will stop the lean motion. Again, to the OP, yes, this is the force you feel pushing you to the outside of the turn.


While I appreciate that you are trying to help the OP to understand the concepts presented, I take issue with the quoted comments.

If you want to turn in a clockwise direction, while moving at counter-steering speeds, not only do you initiate that turn by turning your front wheel to the left, you MUST MAINTAIN a leftside out-tracking in order to continue that clockwise turn. That is, you do NOT 'steer' to the right after initiating the turn, you ALLOW the bike to turn the front wheel to the right, but it MUST continue to point to the LEFT of the instantaneous direction of travel. (See 'Out-tracking' in the glossary.)
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trailrider
Ex-Member

Posted - 07/09/2010 :  12:08 PM
quote:
Originally posted by James R. Davis

When you duck reality by refusing to agree that you only can control speed and direction of travel when riding at counter-steering speeds, and insist, instead, that there is a 'lean control' that consists of steering and speed control, then there is some question in my mind about your sincerity here.
In any discussion (including this one) I'll say what I sincerely believe and when I decide I'm wrong I'll be the first to admit it. Please have no doubt about that. This discussion has been productive for me, hopefully for others who may be reading along.

Both you and Crash make a distinction between two kinds of steering. In the past I've seen Crash mention "direct steering" (presumably in contrast too "counter steering"). Perhaps he means the same thing you are saying but I can't verify that distinction in practice, try as I may. I'm unable devise an experiment to find this distinction. I find changing steering angle has the same effect, at 5 mph or at 10 mph and above. What changes is the amount of lean angle where steering is effective. This morning I did some slow speed maneuvering and noticed something new to me. If I stop the bike, put my feet down, hold the bike in place and turn the wheel side to side while watching the area where the forks connect to the frame, I notice, probably because of rake and trail, when I rotate steering in one direction the rest of the bike, behind the forks shifts and leans in the opposite direction. At higher speeds that weight shift might be unimportant but at very slow speeds when the bike is standing close to zero degrees perhaps that weight shift influences the lean of the bike more than the steering effect. Regardless, I notice that at speeds below 4 mph I seem to use weight shifting to start the bike leaning and if it goes past a few degrees some throttle and more steering is required to stand the bike back up.
quote:
This entire thread is about cause and effect. *You* can cause a change of direction of travel, or a change of speed. As a result of those effects of your efforts, the bike's lean angle will change. That's an effect.
I can cause a change in direction by using the controls to move to and maintain a specific lean angle, depending on the speed. The result is a curving path. So I describe the chain of causes differently but may be we are talking about the same thing and just choose our words differently. What I think I observe is, near zero degrees shifts in my body weight are enough to start the bike leaning one way or another. As lean angle increases steering and throttle become more important to change or maintain a lean angle.
quote:
I defy you to change the lean angle without changing the direction of travel or its speed.
I'm going to have to think about that and do some experiements. When I'm doing 18' diameter circles, usually around 8 mph, I can hold that circle and speed yet vary lean angle slightly by shifting upper body weight side to side.
quote:
I do that with confidence because there is no lean angle control. (By 'lean angle', of course, we are speaking about the lean angle of the COMBINED bike and rider.)
If steering is not lean angle control what is it? When you say combined lean angle of bike and rider I'm confused. What I see, what I feel, is two different lean angles, one for the bike, another for the rider. They are only the same for the instant they pass each other, similar to the way the bike is only standing at zero degrees for the instant it's passing through zero degrees because lean angle is changing continuously, a lot or a little.
quote:
When you categorically deny that there is any difference between the behavior of your bike while turning at sub-counter-steering speeds and while turning at counter-steering speeds, then there is some question in my mind about your sincerity here.
Refer to my earlier comment. I only say what I beleive. "Catagorically deny" is not the right interpretation. If I was so sure of myself I wouldn't be interested in discussing the topic. In the mean time, I notice that as speed decreses steering becomes less effective as lean angle increases. I cannot verify with my own riding that there is some entirely different mechanics involved below a particular speed threshold.
quote:
I defy you to turn your handlebars to the left while moving at 5 mph and cause your bike (and body) to lean toward the right.
I tried that this morning. I'll make a video today or tomorrow.
quote:
Do it at 20 mph and you cannot avoid the lean to the right.
Steering is much more effective an 20 mph than at 5 mph. On my particular bike going in a circle below about 4 mph is extremely difficult because steering is only effect for a few degrees of lean either side of zero. I believe steering works the same way at very slow speeds but only if your balancing skills are good enough to keep the bike very close to zero degrees vertical--difficult for the best riders at very slow speeds.
quote:
I defy you to explain how it is that you can ride on the exact same path through a turn at 20 MPH, then at 40 mph, and then explain to me that increased speed in combination with centrifugal force decreases the lean angle. Or, that decreased speed in combination with centrifugal force increases lean angle.
If I'm understanding correctly that is not consistent with my experience. As speed increases on a given diameter circle I need more lean angle to hold the turn.
quote:
NO NEW STEERING INPUT REQUIRED,
but isn't a new lean angle required, and aren't control inputs needed to establish the new lean angle?
quote:
yet the results are always the same - at counter-steering speeds, braking stands your bike up. You don't have to argue that at 5 mph while driving in a curve, if you slow down your bike leans more or that you can 'save' a falling bike in a curve at 5 mph by increasing your speed as we all know that is true.
In my experience decerating, regardless of brakes, will increase lean angle, not decrease it, regardless of speed. I'll have to do an experiment to see if I can stand the bike up by braking in a turn with no change in steering angle.
quote:
So here is a simple concept for you to play with ... You are riding in a straight line at 50 mph and have removed your left hand from the bars and lifted your fingers from the right grip leaving only the palm of your right hand touching the grip. Now press forward gently with your right hand. What happens to your direction of travel? To your lean angle? How did you input that new steering input you argued about to start you moving to the right instead of to the left?
What I believe, that when I change the steering angle in that situation the bike first begins to lean in the opposite direction. Then something has to intervene to keep the lean angle from increasing so that a turn can begin. That could happen by relaxing the push on the grip, and the wheel turns ever so slightly back in the direction of the turn, enought to stabilize the lean and maintain the turn, or perhaps there is just enough slip in the rear to have the same effect as turning the wheel back into the turn. Something has to stop the lean angle from increasing so the bike doesn't fall.
quote:
And while you are at it ... since you are so strongly of the opinion that centrifugal force pushes you toward the outside of your turn, how do you explain that your bike (and body) actually lean INTO the turn while you are turning?
I would say that the contols are used, by the rider, to lean the bike in the opposite direction from the lean to the outside that centrifugal force would otherwise cause.

Please note, when there's some aspect of this I'm sure I don't understand I say so. I'm also willing to poke holes in my own ideas when I find the opportunity. Understanding is the point here, not winning a debate.
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trailrider
Ex-Member

Posted - 07/09/2010 :  12:40 PM
quote:
Originally posted by James R. Davis

[quote]If you want to turn in a clockwise direction, while moving at counter-steering speeds, not only do you initiate that turn by turning your front wheel to the left, you MUST MAINTAIN a leftside out-tracking in order to continue that clockwise turn. That is, you do NOT 'steer' to the right after initiating the turn, you ALLOW the bike to turn the front wheel to the right, but it MUST continue to point to the LEFT of the instantaneous direction of travel. (See 'Out-tracking' in the glossary.)

And this is the part of your position I can't verify with direct experience. I'm guessing but, I might agree that the direction of the front wheel is always wide of the instantaneous direction of travel if you're trying to account for rear wheel slip, otherwise I'm still clueless. At the first opportunity I'll read about "outtracking".

In the mean time rb's description leaves out a few embellishments I like to include but I can't find the flaw in it. He's right that the bike could be turned vigorously without any leaning--if enough weight could be hung on some sort of outrigger on the inside of the turn.

July 10 edit.

I've read the short description of "out tracking". It's a new wrinkle for me. I'm sure I don't understand it yet. It will take a while to absorb. In my own words, I think the description says out tracking means there needs to be some pressure on the steering to the outside of the turn to counter act a "righting force" that presumably wants to stand the bike up so the net effect is the front wheel is pointing slightly away from the direction of travel, hmmm... I'm not seeing how it fits into the discussion of whether "turning causes leaning".

Edited by - trailrider on 07/10/2010 5:42 AM
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James R. Davis
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Posted - 07/10/2010 :  7:47 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Perhaps it would help to revisit the difference between 'steering' and 'turning'. This, despite the fact that you started this thread doing the same thing.

'Steering' is an input action to cause a change of direction of a vehicle.

'Turning' is a description of a vehicle's path of travel which states that the vehicle is NOT moving in a straight line. It is NOT an input which causes a change of direction. 'Turn', on the other hand, is a description of what a vehicle operator is to do, or of a vehicle path. That is, it can be used to describe either a steering input or a vehicle's non-straight line path.

Centrifugal force is a result of TURNING. Change of direction traveled is a result of STEERING.
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James R. Davis
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Posted - 07/10/2010 :  10:56 AM Follow poster on Twitter  Join poster on Facebook as Friend  
The bike has a center of gravity as does its rider. Since the rider is 'attached' to the bike (loosely), they have a common center of gravity known as their combined CG.

It is the combined CG which is used to determine lean angle.

When a rider moves his body in one direction or the other laterally relative to the bike, the bike moves automatically in the opposite direction such that the lean angle defined by the combined CG does not change whatsoever - which means that leaning the rider's body CANNOT affect the lean angle of the combined CG.

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trailrider
Ex-Member

Posted - 07/11/2010 :  6:19 AM
quote:
Originally posted by James R. Davis

Perhaps it would help to revisit the difference between 'steering' and 'turning'. This, despite the fact that you started this thread doing the same thing.

'Steering' is an input action to cause a change of direction of a vehicle.
I prefer to define steering as changes in the angle between the front wheel and the rest of the bike.
quote:
'Turning' is a description of a vehicle's path of travel which states that the vehicle is NOT moving in a straight line. It is NOT an input which causes a change of direction.
I agree with the slight refinement to say straight path rather than straight line.
quote:
'Turn', on the other hand, is a description of what a vehicle operator is to do, or of a vehicle path. That is, it can be used to describe either a steering input or a vehicle's non-straight line path.
For clarity, I prefer to use the words turn AND turning to describe only the path, not operator actions.
quote:
Centrifugal force is a result of TURNING.
That sounds right to me.
quote:
Change of direction traveled is a result of STEERING.
That would be true of a 4 wheeled vehicle. What I perceive steering does, on a motorcycle, is change lean angle of the bike. The turn results from the combination of lean angle and steering angle.
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James R. Davis
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17286 Posts
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GoldWing 1500

Posted - 07/11/2010 :  7:32 AM Follow poster on Twitter  Join poster on Facebook as Friend  
quote:
quote:
Centrifugal force is a result of TURNING.


That sounds right to me.

quote:
Change of direction traveled is a result of STEERING.


That would be true of a 4 wheeled vehicle. What I perceive steering does, on a motorcycle, is change lean angle of the bike. The turn results from the combination of lean angle and steering angle.



Since centrifugal force is the result of turning and leaning is the result of centrifugal force, especially when it is clear that you can be turning along a path without any steering involved, leaning, yet you persist that steering is what causes leaning, your logic leaves me confused.

Do you really think that motorcycles are somehow unique relative to steering and leaning? Does it not occur to you that ice skaters lean into their turns yet they have no rake and trail built in like a motorcycle does? How about those using something you are more familiar with - roller blades?

STEERING changes the steering angle. Changing the steering angle changes the centrifugal force. While in a turn, changing your speed changes the centrifugal force. That is, EITHER or both steering angle and speed changes will CHANGE the centrifugal force. That includes, NO STEERING along with speed changes.

It follows, then, that steering itself does not CAUSE a lean angle - it merely changes it. On the other hand, turning, by itself, DOES CAUSE LEANING.
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trailrider
Ex-Member

Posted - 07/13/2010 :  5:18 AM
quote:
Since centrifugal force is the result of turning and leaning is the result of centrifugal force, especially when it is clear that you can be turning along a path without any steering involved, leaning, yet you persist that steering is what causes leaning, your logic leaves me confused.
I believe steering is always involved even if there is no deliberate steering input by the rider because, as I mentioned earlier,if the steering was locked, the bike would fall down on the slightest provocation regardless of the maneuver. If I'm right about that centrifugal force appears to be necessary at all times and acting on the bike at all times.
quote:
Do you really think that motorcycles are somehow unique relative to steering and leaning? Does it not occur to you that ice skaters lean into their turns yet they have no rake and trail built in like a motorcycle does? How about those using something you are more familiar with - roller blades?
Roller blades have no built in turning mechanism, no articulating wheels. If they did skates wouldn't be skatable because there would be no way to generate an effective amount of thrust or control the direction of the skate in the glide phase. So the skater turns, not the skate, most of the time by planting a skate at an angle corresponding to a new direction of travel, then leans in that direction, then pushes off in that direction. If you straped a motorcycle to each foot they would only be skatable if the front wheels were locked, which would make rake and trail irrelevent, same as with skates.
quote:
STEERING changes the steering angle. Changing the steering angle changes the centrifugal force. While in a turn, changing your speed changes the centrifugal force. That is, EITHER or both steering angle and speed changes will CHANGE the centrifugal force. That includes, NO STEERING along with speed changes.
There is a third thing that can influence the lean angle of the bike, the rider's upper body weight. That weight is very influential on a bicycle because of it's low mass and less influential on a motorcycle because of it's higher mass. If the front wheel of a bicycle was locked, straight or in a turn, an expert rider might be able to keep it from fallig over by a combination of speed changes and body lean changes but without the influence of both I believe the bicyclist would fall down quickly. On a motorcycle, because of it's higher mass I think that would be impossible for practical purposes. That says to me that speed changes alone would not keep a bike standing, steering changes have to be in the mix, whether deliberate inputs by the rider or changes influenced by the rake and trail geometry of the bike. I could be wrong about this but that's how it seems to me.
quote:
It follows, then, that steering itself does not CAUSE a lean angle - it merely changes it.
And it seems to me that 'causing' or 'changing' are two words to describe the same relationship.
quote:
On the other hand, turning, by itself, DOES CAUSE LEANING.
I started the topic by asking for clarification about "turning causes leaning", not because I disagree, but because I don't understand what that means. Despite this discussion I still don't understand. I'll do some more reading and thinking about it. I'm sure we don't disagree, I'm sure it must be a misunderstanding.
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