Leaning

[chamartia]

Hey, y'all.

Alright, I'm not really that much of a beginner at this point, but I think I should have figured this out by now. So, to the beginner's forum I go. I'm trying to reconcile a few different things:

1. In the MSF Beginner's Course, they tell you to counterweight the bike in low-speed U-turns by maintaining your body upright while leaning the bike under you.

2. In regular turns, you lean to the inside of the turn. By moving the center of gravity of bike+rider to the outside a bit, you decrease the lean needed to make the turn. I ride pretty conservatively, so I don't need the extra lean angle, but I lean because it seems to make things feel more planted.

3. When going around a curve, leaning into the curve, if I need to soften my line a bit (say, a pothole or something), it seems to me that I sometimes stand up the bike a little bit in such a way that leaves me hanging off *more* than before. Essentially, I push the bike towards the outside of the turn, which leaves me further off the bike. This seems to work just fine for softening the line.

Now the questions:
Q1. If turn radius is a function of center of gravity and speed, then wouldn't counterweighting make you lean the bike over further than you would if you stayed in the seat?

Q2. If turn radius is a function of center of gravity and speed, is what I describe in (3) even possible? It seems to me that what I think I'm feeling is physically impossible. If I stand up the bike a bit, but end up leaning further, this seems like it would keep the COG in the same place. Or maybe since the bike weighs about 3.5 times what I do, a shift of bike one direction and rider an equal distance in the other just doesn't cancel out, so the COG still moves enough to change the line sufficiently.

These questions are more of curiosity than anything, borne partially of experiences and partially of watching those videos of cops on Harleys and Japanese guys on VFRs going through the impossibly tight cone courses.

Cheers,
.cyb

[paddy_crow]

The physics behind it are pretty simple. It's not just a function of how far you lean over, but also how far above ground the center of gravity is. The moments have to equal zero for your position to be stable.

Actually, by leaning off the bike to the inside of a turn, the bike doesn't have to be leaned as much. Also, the lower the center of gravity, the less lean angle.

[Mattb4rd]

MSF teaches "Slow, Look, Press, Roll" for "regular" turning.

You sure it was a MSF course you took?  

[AzItLies]

cyb, in response to your 1st premise, the MSF teaches counter-weighting to move your butt and upper body to the OUTSIDE of the turn... thus... counter... weighting... make sense?

Just to be sure that's clear, the bike is leaning into the curve, you are leaning outside of it, in slow tight turns. (think really tight turns, the width of a road, 20 to 24 feet).

to your first Q1: counter-weighting doesn't *make* you lean the bike over more, it *allows* you to so that you can make that tight turn.

re the rest of your thoughts / questions... Seems to me yer over thinking it.

Maybe it would be easier to understand your concerns if you re phrased your question? Is it specifically about those videos? maybe what you want to say is "how do they do that?"

[chamartia]

Hey, y'all.

Thanks for the responses. I'm definitely over thinking it. Because it's fun to do so. If I had problems actually doing any of this, I would be worried about doing it, rather than figuring out what I'm doing. What I'm trying to do is to figure out what I'm doing.

Here's a couple of illustrations, two of which have been posted here before:

V1. Cop, Harley, cone course:


This seems to me pretty much what the MSF teaches as counterweighting. He's not moving his butt, but his upper body goes to the outside of the turn (or, more accurately, it stays upright, what is what I was trying to describe originally).

V2. Gymkhana:


Here, no counterweighting. Just leaning into the turn. This seems to me like it allows him to turn more sharply, because by NOT leaning away from the turn, he ends up with MORE lean angle to use, thus can turn more sharply.

V3. Parking lot knee dragging:


This is the same as the Gymkhana, just a little easier to see, with the rider sticking out his knee.

Now, some elaboration:

E1. With respect to counterweighting (Q1): Let's call leaning into the turn a positive value, and leaning to the outside of a turn a negative value. If you lean the bike over a given amount, say +35degrees, then you can either lean yourself to the inside, say +15degrees, or to the outside, say -15degrees. (Bike+35)+(rider+15) is going to be a sharper turn than (bike+35)+(rider-15), or even (bike+35)+(rider+0), so counterweighting would seem to make the turn slower. The question seems to be one of being comfortable, rather than the physics of the situation.

E2. With respect to adjusting turn radius (Q2): I'm going into a turn at a constant speed, with lean (bike+35)+(rider+15). I then do two things: stand up the bike to (bike+25) and lean off further to (rider+25). The result of this is that the radius of my turn increases. Is the explanation of this simply that the bike is so much heavier than me that when I stand up the bike I move the COG back towards the contact patch, in spite of leaning off more? (If this explanation is correct, then it should be the case that if I were to lean off even more, I would end up maintaining or even decreasing the radius of the turn.)

To reiterate: yes, I am absolutely overthinking this. I was also the only kid on my little league team more fascinated with WHY a spitball works than with the fact that it does. The fascination didn't prevent me from throwing them just fine.

Cheers,
.cyb

[bomber]

you keep talking about the bike and you as if they wereseparate objects -- for the purposes of THIS exercise, consider that they are not.

Physics doesn't care how far you are leaned over, on which side of the bike, nor how far the bike is leaned over.

It cares about the center of gravity of you both. The bike AND you, together.

This is why leaning off at higher speeds mean the bike can be more upright.

Pushing the bike beneather you can work at any speed whatsoever -- just means it'll have to lean more to make up for YOUR COG being more to the outside.

[napper]

The physics and techniques of slow speed turns and high speed turns are totally different.  I.e., countersteering (a term a I don't think you used but I assume you know after taking MSF) doesn't work to initiate a turn below about 20 mph.  Counterbalancing in a street-speed turn would only have the effect of fighting the bike's natural inclination to turn.

[Skee]

My guess is that you are subtly softening up your line when you shift position.

In other words, instead of going from...  
50 total to 50 total [i.e., (bike+35)+(rider+15) to (bike+25) + (rider+25)],
you are actually going from...
50 total to 40 total [i.e., (bike+35)+(rider+15) to (bike+20) + (rider+20)].  

How are you measuring the lean angle anyway.  After seeing a large number of pics of myself leaned over in corners, I can tell you that at least my judgement of my own lean angle is neither accurate nor quantitative. I also spent a lot of time as a kid wondering about important stuff like how spitballs work.  Never could explain it.  But I'm pretty sure I've identified the causative agent behind the wind buffeting on my Wee.  

[paddy_crow]

The physics and techniques of slow speed turns and high speed turns are totally different.  I.e., countersteering (a term a I don't think you used but I assume you know after taking MSF) doesn't work to initiate a turn below about 20 mph.  Counterbalancing in a street-speed turn would only have the effect of fighting the bike's natural inclination to turn.

Physics don't change with increased velocity. Techniques, yes, but not physics.

[chamartia]

My guess is that you are subtly softening up your line when you shift position.

In other words, instead of going from...
50 total to 50 total [i.e., (bike+35)+(rider+15) to (bike+25) + (rider+25)],
you are actually going from...
50 total to 40 total [i.e., (bike+35)+(rider+15) to (bike+20) + (rider+20)].

How are you measuring the lean angle anyway.  After seeing a large number of pics of myself leaned over in corners, I can tell you that at least my judgement of my own lean angle is neither accurate nor quantitative. I also spent a lot of time as a kid wondering about important stuff like how spitballs work.  Never could explain it.  But I'm pretty sure I've identified the causative agent behind the wind buffeting on my Wee.

Yeah, it's certainly possible that the saddle perspective isn't the best for judging lean angle. It's not like I'm dragging a knee here to give me a point of reference. But I would be more confident about feeling how far I'm hanging off. And there, it seems like the likely explanation is just that leaning the bike over or standing it up has a much greater effect on COG than hanging off a bit more or less.

Here you go for spitballs:

http://www.amazon.com/Spitter-Autobiographical-Confession-Gaylord-Perry/dp/0841502994

That just leaves counterweighting, which I still don't get. One last pass:

Parking lot speed, so no talk of countersteering.
You turn the wheel a bit and initiate a turn.
If you lean into the turn, gymkana style, the bike will be leaned over less.
If you stay upright in the saddle, moto-cop style, the bike will be leaned over more.

Hypothesis: at a given lean angle and speed, counterweighting will always increase your turn radius, in the parking lot just like on the road.

That seems right to me. Then I might guess that the MSF folks teach counterweighting because it's not very comfortable (in a 'freak out I'm going to fall over sense) to lean into a low-speed turn, but that counterweighting is actually counterproductive.

So what am I missing here?

Best,
.cyb

[dark_isz]

A good explanation of counter-balancing at low speeds:

http://www.msgroup.org/forums/mtt/topic.asp?TOPIC_ID=311

Basically, counter-balancing allows for more lean angle, more lean angle means a tighter radius.

[Cablebandit]

 I'm definitely over thinking it. Because it's fun to do so.

Are you a SWRiverstone Jr in training?  

[trippin]

You must be one with the bike, Young Skywalker.

[JonUSN]

 

just ride the damn thing

[bikerfish1100]

That just leaves counterweighting, which I still don't get. One last pass:

Parking lot speed, so no talk of countersteering.
You turn the wheel a bit and initiate a turn.
If you lean into the turn, gymkana style, the bike will be leaned over less.  If you stay upright in the saddle, moto-cop style, the bike will be leaned over more.

Hypothesis: at a given lean angle and speed, counterweighting will always increase your turn radius, in the parking lot just like on the road.

That seems right to me. Then I might guess that the MSF folks teach counterweighting because it's not very comfortable (in a 'freak out I'm going to fall over sense) to lean into a low-speed turn, but that counterweighting is actually counterproductive.

So what am I missing here?

Best,
.cyb

counterweighting allows the bike to be leaned more, and that greater lean is what makes the bike turn tighter. counterweighting works, just as we teach it.
try this. ride your bike in as tight a circle as you can. bars at full lock. now, counterweight off the saddle to the outside. maintain same speed. yu will have gained ground clearance between bike and ground. now increase your lean angle. bike will turn a tighter circle.
you are waaaay overthinking this.

[Cablebandit]

Then I might guess that the MSF folks teach counterweighting because it's not very comfortable (in a 'freak out I'm going to fall over sense) to lean into a low-speed turn, but that counterweighting is actually counterproductive.

So what am I missing here?

You figured it out.  Us MSF folks like injuring people, repairing busted bikes, and filling out paperwork. 

Lean into the turn at parking lot speeds and fall over.  There's your lesson.  If you don't want to fall over don't do that again.  Those Japanese videos you're watching are at much higher that "parking lot" speeds and they are on the verge of falling over most of the time.   

[cbsnbiker]

Hey, y'all.

Alright, I'm not really that much of a beginner at this point, but I think I should have figured this out by now. So, to the beginner's forum I go. I'm trying to reconcile a few different things:

1. In the MSF Beginner's Course, they tell you to counterweight the bike in low-speed U-turns by maintaining your body upright while leaning the bike under you.

2. In regular turns, you lean to the inside of the turn. By moving the center of gravity of bike+rider to the outside a bit, you decrease the lean needed to make the turn. I ride pretty conservatively, so I don't need the extra lean angle, but I lean because it seems to make things feel more planted.

3. When going around a curve, leaning into the curve, if I need to soften my line a bit (say, a pothole or something), it seems to me that I sometimes stand up the bike a little bit in such a way that leaves me hanging off *more* than before. Essentially, I push the bike towards the outside of the turn, which leaves me further off the bike. This seems to work just fine for softening the line.

Now the questions:
Q1. If turn radius is a function of center of gravity and speed, then wouldn't counterweighting make you lean the bike over further than you would if you stayed in the seat?

Q2. If turn radius is a function of center of gravity and speed, is what I describe in (3) even possible? It seems to me that what I think I'm feeling is physically impossible. If I stand up the bike a bit, but end up leaning further, this seems like it would keep the COG in the same place. Or maybe since the bike weighs about 3.5 times what I do, a shift of bike one direction and rider an equal distance in the other just doesn't cancel out, so the COG still moves enough to change the line sufficiently.

These questions are more of curiosity than anything, borne partially of experiences and partially of watching those videos of cops on Harleys and Japanese guys on VFRs going through the impossibly tight cone courses.

Cheers,
.cyb

If you think of yourself and the bike as one unit, but that can be positioned in different ways, that may help you understand things better.

Envision taking a turn at a particular speed and a particular radius, keeping your body even with the bike. You will achieve a particular lean angle.

If you take the turn at the same speed and turning radius, but lean your body to the outside of the turn, the bike will lean more.

If you take the turn at the same speed and turning radius, but lean your body to the inside of the turn, the bike will lean less.

Why does the MSF advocate counterweighting at low speeds? Here's one way to think about it. What does a motorcycle need to do to turn? It needs to lean. How much does a motorcycle lean at low speeds? Not much. How can we help the turning process? By counterweighting.

Here's another thing to try. Stand by your motorcycle, hold it vertical, turn the handlebars full lock left, and turn it in a circle. After you've done this, lean the motorcycle as far as you feel comfortable, turn the handlebars full lock left, and again turn the bike in a circle. Measure the radii of the two circles. What do you notice?

(There are other factors, but this is a start.)

A good explanation of counter-balancing at low speeds:

http://www.msgroup.org/forums/mtt/topic.asp?TOPIC_ID=311

Basically, counter-balancing allows for more lean angle, more lean angle means a tighter radius.

I didn't slog through that particular message on msgroup. That particular message may be correct, incorrect, or a mixture of the two. However, I'll observe that there is a bunch of bad info on that website. Caveat emptor.

[chamartia]

If you take the turn at the same speed and turning radius, but lean your body to the outside of the turn, the bike will lean more.

If you take the turn at the same speed and turning radius, but lean your body to the inside of the turn, the bike will lean less.

Why does the MSF advocate counterweighting at low speeds? Here's one way to think about it. What does a motorcycle need to do to turn? It needs to lean. How much does a motorcycle lean at low speeds? Not much. How can we help the turning process? By counterweighting.



(There are other factors, but this is a start.)

Sorry for the delay in responding, but I did want to thank you for this reply. It gets at what I was trying to get at: if speed is constant, then radius decreases with lean. But body lean and bike lean can vary independently of one another. Thus the question of what counterweighting does: it increases bike lean by decreasing body lean, but presumably the increase in bike lean outweighs the decrease in body lean, so that radius decreases.

Best,
.cyb

[AzItLies]

Sorry for the delay in responding, but I did want to thank you for this reply. It gets at what I was trying to get at: if speed is constant, then radius decreases with lean. But body lean and bike lean can vary independently of one another. Thus the question of what counterweighting does: it increases bike lean by decreasing body lean, but presumably the increase in bike lean outweighs the decrease in body lean, so that radius decreases.

Best,
.cyb

And it varies with speed. Slower speeds above is correct. Faster speeds we lean in (or off) to keep the bike more upright, allowing for the faster speed and tight radius.

It's really all about centrifugal force. At slower speeds, on a (top) heavy bike (especially), you have to counterweight, due to the lack of centrifugal force.

enjoy,

[cbsnbiker]

Sorry for the delay in responding, but I did want to thank you for this reply. It gets at what I was trying to get at: if speed is constant, then radius decreases with lean. But body lean and bike lean can vary independently of one another. Thus the question of what counterweighting does: it increases bike lean by decreasing body lean, but presumably the increase in bike lean outweighs the decrease in body lean, so that radius decreases.

Best,
.cyb

I'm not a scientist, so I can't quantify exactly what happens.

You can ride the same radius circle at the same speed, and adjust how much the bike leans with your body.

I'm curious -- did you try the exercise I mentioned in a previous message? I'll repeat it here:

Here's another thing to try. Stand by your motorcycle, hold it vertical, turn the handlebars full lock left, and turn it in a circle. After you've done this, lean the motorcycle as far as you feel comfortable, turn the handlebars full lock left, and again turn the bike in a circle. Measure the radii of the two circles. What do you notice?