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Discussion Starter #1
In one of Keith Code's articles titled, Body position, he talks about his first "law" of body positioning which is "Stability Comes in Pairs. Bike and rider stability are always paired―rider instability transfers directly to the bike."

What do you think he means when he says that rider instability transfers directly into the bike? What kinds of things can show up in someones riding if they are unstable on their bike?

The full article can be found here:
 

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IM THE BRONZE
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In one of Keith Code's articles titled, Body position, he talks about his first "law" of body positioning which is "Stability Comes in Pairs. Bike and rider stability are always paired―rider instability transfers directly to the bike."

What do you think he means when he says that rider instability transfers directly into the bike? What kinds of things can show up in someones riding if they are unstable on their bike?

The full article can be found here:
I think he's referring to a riders incorrect body position and control will make the bike unstable.
A riders weight has a great effect of how a bike handles.

In a 300lb car you can lean left or right cornering and you wont notice anything.

Lean far left or right on a motorcycle, it makes a huge difference.
Leaning forward or backward exiting a corner on the throttle make a huge difference in weight transfer.
 

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I know things... A lot of things.
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Well, it's hard to know what such statements mean, as they're mostly not very precisely worded. For instance, I'm not sure how to interpret the concept of an 'unstable rider', unless perhaps as a rider for falls (or jumps) off the bike.

In any case, interpreting it as meaning that the rider has an impact on the stability of the machine-rider system, then that is certainly the case and there are many ways in which that happens. One is, as Geesxara notes, that the rider can, to a substantial degree, affect the center of mass of the system. This can then induce load transfer, change the geometry and hence the stability and handling characteristics of the machine. This is the purely static viewpoint (i.e. where we consider what happens after the new configuration has been achieved, after say the rider has shifted violently to left of the center plane of the bike and is now hanging off, the machine having achieved equilibrium once more).

A perhaps equally important aspect, has to do with the dynamic response of the system, where violent shifts of the rider's body, will necessarily be accompanied by reactions on the chassis, unsettling it in many ways, which are too complex for me to talk about, but which should be confined to the transient period during which the rider is moving, unless they destabilize the machine to the point of starting a wobble or weave perhaps.

All the above has assumed changes of the rider's body position, which have not fed back into the steering column. If you shift your body and push against the grips to do so, then it will have obvious destabilizing effects on the machine; obvious, that is, while contemplating them, although they may well be far from obvious while actually causing them. For instance, braking and bracing yourself against the grips, may well feel like the bike is becoming unstable due to an impending wheel lock.

Instead of inadvertently actively forcing the grips (due to reasons such as the above), you might also affect the machine by fighting the forces fed back to the steering column from the road, due to the bike's geometry. For instance the caster geometry of the front wheel has a self-stabilizing effect, which works by pushing the wheel (and hence steering column) into alignment, as soon as it rotates away from the direction of the bike's motion. This is counteracted by such things, as the friction in the head bearings, the steering damper and to some degree your hands, which are generally expected to introduce some damping force. If you maintain a death grip on the grips though, say because you've become rigid due to panic, or because you're keeping your arms straight and support your body on the grips, then you're fighting (or perhaps downright preventing) that stabilizing effect of the front wheel geometry, causing the bike to become more unstable.

This all assumes purely dynamic effects, and ignores the equally important case of plain old bad input, such as chopping the throttle, pushing too hard on the bars while turning, etc. and there are probably other ways, in which a rider can cause a well-engineered modern machine feel like a scooter from the fifties, which are escaping me.
 

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Dreaming of buttsecks for years...
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I think what he means is that the bike is sensitive to the rider. If you've got good body position, you're locked in and loose, you're stable. If you're fighting the bars or bouncing around, that will translate to the bike.

The only example I can give is pulling/pushing on the bars during acceleration or braking. That tight grip on the bars is never good. Lose grip on the bars and using your core/lower body is correct. The bike just doesn't respond well to being muscled around.
 

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Discussion Starter #5
I think what he means is that the bike is sensitive to the rider. If you've got good body position, you're locked in and loose, you're stable. If you're fighting the bars or bouncing around, that will translate to the bike.

The only example I can give is pulling/pushing on the bars during acceleration or braking. That tight grip on the bars is never good. Lose grip on the bars and using your core/lower body is correct. The bike just doesn't respond well to being muscled around.
Yes, agreed. The bike is very sensitive to the rider so if the rider is making any extra or unwanted inputs into the bike, the bike will become less stable then if those inputs weren't there. A rider gripping the bars too tightly can cause instability and as dpapavas put, "chopping the throttle, pushing too hard on the bars while turning, etc. and there are probably other ways, in which a rider can cause a well-engineered modern machine feel like a scooter from the fifties". So that being said, how do you ensure that a rider is "Stable" on the bike so that they don't end up putting unwanted inputs into the bars or other controls?
 

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Chubby Chaser
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Smooth inputs is key. Smooth application of brake/throttle/steering, as well as body movements around the bike. Doing any of those things abruptly will upset the balance of the motorcycle and ultimately result in you having to fight the bike to get it back in line....which ultimately costs you speed/time.
 

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So that being said, how do you ensure that a rider is "Stable" on the bike so that they don't end up putting unwanted inputs into the bars or other controls?
This is not really a question of "what to do, or not do", but what approach to follow to decide "what to do, or not do". There are many riders and bikes and, while there's a lot of advice that may be universally valid, that is not always the case. Some advice is even universally invalid.

So, as far as I can tell, one has to start by assuming that when something doesn't feel right, it's due to rider error. That is not always the case, but it usually is, with the kind of machines we have today, and if it turns out not to, one will have a lot and be in a better position to troubleshoot the equipment. The next step, would be to try to analyze the situation, by trying to notice, how the bike responds to the actions of the rider. Needless to say, one should ride under very comfortable and controlled conditions during such analysis, as much of the rider's attention, will be shifted off the road.

This process is compounded of course, by the fact that it's usually hard to accurately sense exactly what you're doing (for instance you might be having too tight a grip on the bars, without noticing it, because your attention is on the brakes) and that it's hard to gauge what the bike is doing, as most reactions of the machine, (save for exaggerated ones, such as having the wheels lock), will feel "unstable", but not much more specific than that. I'm sure it's possible for more experienced riders, to perceive deeper, but it if you have that sort of experience, this answer is not for you (and none I can give is).

So it's a good idea to read up and research books and the Internet for advice, then try to analyze it and see if it seems to be correct or not. For instance, if someone tells you that you shouldn't support your weight on the bars, then you can set aside a few sessions of riding and try to consciously support your weight with your core muscles, keeping a very relaxed hold of the steering. Focus just on that and see what difference it makes. You can then try to consciously throw your weight on the bars and see what happens. The key is to do all this under controlled (so as to be safe) and familiar (so as to know what to expect and whether the response differs) conditions and to examine only one thing at a time. And of course, always exercise caution and try out changes in small steps.

Apart from that, it's all practice, I suppose.
 

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Rectum Rupticus
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I seem to remember somebody many years ago Preaching Being Smooth . :grin2:
 

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Discussion Starter #14
So that being said, how do you ensure that a rider is "Stable" on the bike so that they don't end up putting unwanted inputs into the bars or other controls?
There are things that riders can do to help get them more "stable" overall on their bike. For example, by locking an outside knee (or both knees) into the tank cutout you can almost hold on to the bike with your lower body which allows your arms to remain more relaxed. Without that added stability from gripping the tank with your legs it can sometimes be nearly impossible to not have a death grip on the bars.

Under hard braking, I squeeze the tank with both knees and also work on have good BP to help keep me as stable and smooth as possible.

Sometimes it can be really hard to be smooth on the throttle and/or the brakes if you are only holding onto the bike with your arms!

And the added stability also helps on bumpy roads or over rough surfaces.
 

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The only example I can give is pulling/pushing on the bars during acceleration or braking. That tight grip on the bars is never good. Lose grip on the bars and using your core/lower body is correct. The bike just doesn't respond well to being muscled around.
A classic mistake is trying to change position on the bike while turning into the corner or while picking up the bike. One of the first things you learn on the track is to adjust your body position while in a straight(ish) line so as you actually enter the corner you are already in the correct position.
 

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I would half way agree with that statement. For the lower half of your body, yes. But from the waste up, I move a lot.
 

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Discussion Starter #17
A classic mistake is trying to change position on the bike while turning into the corner or while picking up the bike. One of the first things you learn on the track is to adjust your body position while in a straight(ish) line so as you actually enter the corner you are already in the correct position.
Absolutely, the sooner you can get your body position set up the better. The more stable you are with your lower body, the more relaxed you can be with your upper body. What are some of the things you do with your lower body to get set up for the corner?

I would half way agree with that statement. For the lower half of your body, yes. But from the waste up, I move a lot.
What is it that you are doing with your upper body that requires you to move a lot? Can moving around adversely affect the motorcycle and/or your riding?
 

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Adjusting balance. As I get closer to the apex, my shoulders and head go further away from the center line of the bike. It's all a balancing act.
 

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I would half way agree with that statement. For the lower half of your body, yes. But from the waste up, I move a lot.
As I read and watch tutorials I see similar things being said. Get the BP set but you can adjust upper body as needed in the curve. Like if you need to tighten up the turn you bend that inside elbow more and drop the upper body out/down more.
 

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Discussion Starter #20
Adjusting balance. As I get closer to the apex, my shoulders and head go further away from the center line of the bike. It's all a balancing act.
Do you need to adjust your balance every corner every time? If you move your upper body further away that means that you have to move it back when you go the other direction correct? Could you not drop your upper body over that far each and every time? (See comment below)

As I read and watch tutorials I see similar things being said. Get the BP set but you can adjust upper body as needed in the curve. Like if you need to tighten up the turn you bend that inside elbow more and drop the upper body out/down more.
Absolutely. AS NEEDED. We coach this at the California Superbike School as an exercise called Hook Turn. if you are are already leaned over and need to tighten up your line you can drop your upper body over and down more without adding extra lean angle but it isn't necessary each and every time. When you ride you want to eliminate any unnecessary movements and make the movements you do make as slight and efficient as possible. I see it all the time with students wasting energy hanging way off the bike and then having to move ALL THE WAY over to the other side. If you drop your upper body over and down low each and every time then you waste energy but you also don't leave yourself any margin if you do need to tighten your line. I only move my body over as far as necessary for the corner and the speed.

I just came home from coaching for 5 days at Barber Motorsports Park where I worked with a student on exactly that. Only move as far as you need to save energy and maximize efficiency :grin2:
 
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