Talk:Countersteering

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Contents 1 Definition 2 Text from counter-steering article 3 steering geometry 4 Contradiction 5 Angle vs Camber Angle 6 Language 7 Walking speed 8 Better not give two different explanations for one thing 9 Gyroscopic effects 10 Very low speed 11 Physical experiment 12 Possible inter-Wiki Link 13 Fascinating bit of OR

[edit] Definition

You push in the direction you want to turn. The "counter" part refers to the fact that you are actually turning the handlebar in the opposite direction when you do that, so that is probably what is was intended to say by that change that was made. I remember from the Motorcycle Safety Foundation course that pushing in the direction you want to turn makes it more intuitive and therefore easier to remember. I have corrected the article back to my original and merged counter-steering into this article.Spalding 04:13, Dec 8, 2004 (UTC)

I don't think the cleanup tag is justified - between my explanation and the external link, I think it is clearly and logically explained. Spalding 17:10, Feb 4, 2005 (UTC)

[edit] Text from counter-steering article

The following text from User:Manning Bartlett has been copied from the counter-steering article to merge it into this article:

I sat down with all good intentions of writing this article. But as soon as I began to research the various web-pages, I quickly realised that I was out of my depth physics wise.

So here are some links that may benefit a proper physics person to explain this baffling phenomenon. The pages all seem to disagree with each other as to what causes it.

[1] [2] [3]

[edit] steering geometry

I have looked at the three articles of the three links above. All three of them are in perfect agreement, but the third article discusses the physics in much greater depth.

To expand the wikipedia article, the dynamic behavior of the steering geometry would have to be discussed. The forefork designs of bicycles are little miracles of engineering: if the proportions are just right the steering geometry makes for a forgiving balance behavior of the bike, and it enables smooth steering. By contrast, a bicycle with a vertical steering column would be an absolute nightmare to steer.

Actually, experiment proves otherwise. See The Naïve Bike easily capable of being ridden AndrewDressel 00:01, 19 May 2006 (UTC)

To some motorcyclists it may appear as if their front wheel reads their mind, steering in the direction they want to go. Generally motorcyclists feel that they are thinking themselves through a curve.

A bike is steered by shifting its balance; the front wheel follows these shifts.

Direct experimentation by California Superbike School suggests the opposite. AndrewDressel 03:20, 19 May 2006 (UTC)

The balance is manipulated with well-timed, minute turns of the front wheel. --Cleon Teunissen | Talk 20:31, 10 Mar 2005 (UTC)

[edit] Contradiction

Anyone notice that paragraph two, about gyroscopic effects, appears to be contradicted by the rest of the article?

"Motorcycles turn corners using the gyroscopic roll reaction force of the spinning front wheel."

vs

"If a biker wants to turn to the right, he first throws the bike off balance by a well-timed jolt to the handlebars, momentarily pointing the front wheel slightly to the left. The center of mass of the bike plus rider will continue in a straight line, but the contact patches of the tires move to the left with respect to this straight line."

So, is it one, the other, or both? AndrewDressel 03:28, 19 May 2006 (UTC)

Not to mention that precession rate is inversely proportional to spin rate. That means that if "gyroscopic roll reaction" is really the mechanism, it happens twice as slow at 60mph as it does at 30mph. That doesn't sound desirable. Does anyone have a reference to someone who has done the math? AndrewDressel 13:10, 19 May 2006 (UTC)

Since the section about the "gyroscopic roll reaction force" remains unsupported, I've taken it out. I also removed the assertion that countersteering is actually "push steering". Perhaps is it "also known as" or "might better be thought of", but it certainly isn't "actually push steering" any more than it is "actually pull steering". AndrewDressel 12:53, 23 May 2006 (UTC)

[edit] Angle vs Camber Angle

I took out camber angle as it is defined as "the angle made by the wheel". While this is true, it is insignifigant in this context. It is the angle of the entire vehicle that matters: specifically the angle made between a horizontal plane and the plane defined by the two wheel contact points and the combined center of mass of the rider and vehicle. AndrewDressel 14:12, 6 June 2006 (UTC)

[edit] Language

• Tried to make it sound less like a motorcycle riding school lecture.
• Removed mention of "conventional steering" as it contradicts the assertion that "At low speeds countersteering is equally necessary, but the countersteering is so subtle then that it drowns in the continuous corrections that are made in balancing the bike."
• Softened the distinctions between bicycles and motorcycles and focused more on the increased need to consciously countersteer as speed increases.

AndrewDressel 13:30, 14 June 2006 (UTC)

[edit] Walking speed

125.209.173.112 added "above walking pace", but I know of no reason why the physical requirement for countersteering is bounded. Unless someone can find a reference that has shown by physical experiment or some mathematical calculation that countersteering becomes unnecessary, this addition should be reverted. -AndrewDressel 01:37, 23 August 2006 (UTC)

-No reference found, so addition removed. -AndrewDressel 00:37, 25 August 2006 (UTC)

Motorcycles and bicycles are "inverted pendulums" and must be balanced laterally regardless of speed. The fact that many do not notice it at lower speeds is akin to people not noticing how their body balances itself when walking or standing on a line, and then make the leap that it must not exist.

Further, if such a transition speed did exist (say 8mph) where below which one steers and above which one countersteers, no one has stated how the bike is turned AT 8mph, which direction, how quickly (roll rate), and how tightly.

[edit] Better not give two different explanations for one thing

In the current version of the article it is stated:
"Otherwise the bike and rider's inertia or centrifugal force (depending on your frame of reference) will tip the bike over towards the outside of the curve."
I propose to replace that with:
"Otherwise the bike and rider's inertia will tip the bike over towards the outside of the curve."

The remark about dependency on the frame of reference is unhelpful, I think. It suggests there are two different explanations for the tipping over: either inertia or centrifugal force. But the expression 'centrifugal force' is just a very roundabout way of talking about inertia.

If the bike plus rider fails to lean sufficiently inward, then the center of mass of the bike will follow a less sharp curve than the wheels, and consequently the bike will tip over to the outside of the curve. --Cleonis | Talk 05:53, 25 August 2006 (UTC)

After reading the centrifugal force article, I'd lean towards "Otherwise centrifugal force will tip the bike and rider over towards the outside of the curve." From the point of view of the rider, centrifugal force, psuedo or not, is straight forward and easy to understand. I'd leave the wrangling about inertia to other articles. -AndrewDressel 22:35, 25 August 2006 (UTC)

I favor saying things in a straightforward and consistent way. Don't add unnecessary complexity. Take the example of braking: if a front wheel has a lot of stopping power, a motorcycle may flip over when the rider brakes too hard. The cause of flipping over is twofold: the grip of the front wheel, and the inertia of the motorcycle. It would be very weird to claim that the motorcycle, braking too hard with the front wheel, is flipped over by "the forward force". It's the motorcycle's inertia. The straightforward thing to say about steering into a curve without enough lean is that the danger of flippng over is due to the inertia of the motorcycle. --Cleonis | Talk 00:29, 26 August 2006 (UTC)

Well, there we disagree. In the case of braking, in the initial explanation, it is enough to mention the front wheel's stopping force. In the case of turning, I prefer to mention only centrifugal force. It is the two-word phrase commonly used to represent the effect of inertia of an object in circular motion, as explained in the centrifugal force article. It is especially a concept that "those inside the car will often find natural". -AndrewDressel 02:53, 26 August 2006 (UTC)

If it helps to clarify, the combined mass of the bike+rider will continue in a straight line as the tires' contact points track out and away from under that mass along the curve. Using the term "centrifugal" implies "center-fleeing" and thereby that the rider+bike track along a curve opposite that of the wheels, a common mis-perception that should not be perpetuated no matter how common it is -- that's the point of Wikipedia, no? Inertia does not TIP the bike so much as countersteering TRIPS the bike like pulling the rug out from under one's feet.

I think you are refering to something else. The above discussion was about how to explain why it is necessary to lean in a turn. Your comments appear to be about how that lean is initiated. -AndrewDressel 02:38, 22 March 2007 (UTC)

[edit] Gyroscopic effects

Gyroscopic effects do play a role in bike steering, I think, but it is a rather technical issue, more suitable for a more technical exposition of than for the wikipedia article

In order to get to the required lean, the bike must roll. The front wheel acts like a gyroscope wheel: when there is roll, the wheel's gyroscopic response is to yaw. (For definitions, see pitch, roll, yaw.) I rather suspect that this contributes to the fact that it is possible to steer a bicycle accurately without hands on the handlebars. I also suspect that the gyroscopic effects contribute to the experience of effortlessness of well executed countersteering. --Cleonis | Talk 06:20, 25 August 2006 (UTC)

The gyroscopic effects are discussed in the Bicycle and motorcycle dynamics article. Countersteering is just about the steering input required to initiate a turn. -AndrewDressel 14:54, 25 August 2006 (UTC)

[edit] Very low speed

I have removed the sentence "So at very slow speeds, the bike can be steered while completely upright like a car, involving no countersteering." added by 82.47.85.24

The assertion of "completely upright" is simply wrong because by being in a turn at all, a bike and its rider will experience centrifugul force that must be counteracted by leaning. There are no exceptions.

That the lean angle is very small or that the handlebars are turned far in the direction of the desired turn does not mean that the momentary countersteering necessary to initiate that lean can be skipped. -AndrewDressel 14:52, 3 October 2006 (UTC)

I'm a farily experienced (motor)bike rider, and at very low speed, say walking pace, you do not countersteer (or at least it's optional), even to lean. Dave 04:23, 28 October 2006 (UTC)

How then do you create the necessary lean? -AndrewDressel 03:13, 29 October 2006 (UTC)

At the lowest speeds, you don't lean. Dave 17:01, 29 October 2006 (UTC)

Then how do you counter the Centrifugal force? -AndrewDressel 19:54, 29 October 2006 (UTC)

I don't see why it needs countering - tyre sidewalls should surely take it, as far as I know there's no reason why resultant force on the bike need be vertical (with respect to the bike). Dave

The reason the resultant force (sum of all forces) needs to be vertical with respect to the the bike (exactly coincident with the plane defined by the two wheel contact points and the combined center of mass of the bike and rider) is to keep the bike from falling over. I don't know what you mean by "tyre sidewalls should surely take it." -AndrewDressel 22:01, 29 October 2006 (UTC)

On reflection, as counter intuitive as it seems you must be right, as I can't see any other way there wouldn't be a resultant moment around the centre of mass. Dave 13:34, 30 October 2006 (UTC)

I think what trips us all up is how at lower and lower speeds the necessary but decreasing countersteering becomes overwhelmed by growing adjustments required simply to maintain balance. We are able to unconsciously take advantage of random, minute leans in the desired direction. I guess one could argue, in that case, that conscious countersteering becomes unnecessary. However, in the ideal case of well maintained balance, as I argued with you, there is not a point at which all countersteering become unnecessary. -AndrewDressel 18:21, 31 October 2006 (UTC)

Very simply, a bike is an "inverted pendulum" which must be balanced laterally (side to side) regardless of speed. Personally, I easily have over 200,000 miles on motorcycles on various surfaces (paved, dirt, gravel, grass, snow, ice), won numerous slow races (>1mph races where the goal is to be the LAST one to cross the finish line with out leaving your narrow lane nor putting a foot down) and also teach motorcycle classes.

When executing a tight U-turn from a straight line on level ground in fresh snow at dead slow speeds (due to the vey limited traction), the evidence of countersteering can still be seen in the tracks where the front wheel always tracks first to the side of the straight line AWAY from the desired direction of turn. This can also be done with wet tires on dry pavement and the use of a chalk line snapped onto the ground. Though the amount of countersteering decreases with slower speeds and wider turns, it remains present though often overlooked.

[edit] Physical experiment

"The physical countersteering phenomenon without use of the countersteering technique is illustrated by the following simple experiment: Balance a bicycle by walking in a straight line and only holding on to its saddle, then initiate a turn by leaning the saddle in one direction. One should observe the front wheel momentarily flopping in the opposite direction of the turn before turning in the direction of the turn." - Ilanpi (13:57, 7 January 2007)

- I do not recall seeing this in print before. Is there a source we can cite? -AndrewDressel 16:57, 8 January 2007 (UTC)

- This effect is counter to that created by gyroscopic forces of the spinning front wheel, and I suspect this must depend on the geometry and mass distribution of the front end and the rate of the induced lean. Do any details exist of what conditions must exist for this to work? -AndrewDressel 16:57, 8 January 2007 (UTC)

- Nice clarification of the two possible interpretations of the term, by the way. -AndrewDressel 17:02, 8 January 2007 (UTC)

The sequence described by Ilanpi is different from what I would expect. There is also the following awkwardness: in walking beside a bicycle, and tipping it over, the leverage for tipping it over came from the feet resting on the pavement. So this example raises a question as much as it attempts to answer one: where does the leverage for tipping the motorcycle come from? In the case of a motorcycle driven at speed, gyroscopic effects become significant. Because of the bike's tendency to remain upright (gyroscopic effect) it is hard to tip it sideways, but at the same time it gives the rider the leverage to really shift his weight, say to the right, and subsequently tip the bike to the right with his sheer weight. However, a bicyle weighs much less than its rider so the leverage due to gyroscopic effects is insignificant. If, when riding a bicycle, I tip my upper body to the right, the bicycle tips to the left as there is no leverage to shift the common center of mass; the common center of mass keeps going in a straight line. As described in the article, when the technique of countersteering is used to prepare for cornering, the center of mass keeps going in a straight line, and the contact patches of the tyres are moved away from the straight line. --Cleonis | Talk 13:07, 9 January 2007 (UTC)

Even though the center of mass of the entire system does not lean, when torque is applied between bike and rider, the bike does lean, at least in the case of light and/or slow bikes, and so the front end does react. The question, for me, is whether the front end reacts as Ilanpi describes. I can see it happening of the center of mass of the front end is sufficiently forward of the steering axis and the lean is induced rapidly enough. Then the front end will lag behind the lean, due to its inertia, and effectively steer opposite the lean momentarily until other factors cause it to steer towards the lean. However, all this guessing doesn't really matter if we can't find a citable source, right? In fact, the existing physical experiment I already cite, the "No B.S. Machine", claims the opposite: rider lean by itself cannot steer a motorcycle. -AndrewDressel 17:48, 9 January 2007 (UTC)

I agree that it doesn't matter if no citable source is available.

I just read the "No B.S. Machine" webpage. That looks very convincing to me. The modified motorcycle's front wheel is freed to follow the lean of the bike. I think that modified bike is very effective in demonstrating to people they have made the wrong attribution: all the time they have actually been employing countersteering. ::::That said, on a smooth surface, a bicycle can be steered hands-free very accurately. The principle is the same: first the bicycle is thrown off balance, then the front wheel follows.

By the way, I also own a uni-cycle. I never became any good at riding it, but I learned enough to experience that the only way a uni-cycle can be steered is through camber steering. In the case of a motorcycle, if the tires are quite fat and round, camber steering will make a significant contribution. --Cleonis | Talk 18:58, 9 January 2007 (UTC)

Andrew notes that No-B.S. reveals, "rider lean by itself cannot steer a motorcycle." That is exactly true. As I added in my edit at the top of this article, countersteering "is the only way a rider can cause a single-track vehicle at speed to turn." When novice riders take an MSF Basic RiderCourse from me, every one of them understands this concept before the course is over. "Press right to go right, press left to go left." I do not understand why it can be so difficult for experienced riders to understand this. When riding a motorcycle, all one needs to do is try it in order to believe it. Once one understands this, one has in hand a powerful technique in the operation of a motorcycle. Jeff dean 00:05, 10 January 2007 (UTC)

As the feedback slows to a trickle, I've tried to clean things up a bit. I'll leave in most of the addition, but remove the, as yet, unsourced experiment. I'd love to find more details about that. -AndrewDressel 19:18, 11 January 2007 (UTC)

Sorry if I've been imprecise. I made up this experiment and performed it under non-scientific conditions (and by my students at Stanford under similar conditions) so it doesn't have the validity required for this article. However, I believe it reflects the truth and I leave it here as a "thought experiment." I completely disagree that a motorcycle cannot be steered by body weight alone. The reason is that a bicycle can easily be steered no hands and there is no qualitative difference between a bicycle and a motorcycle as regards balance, apart from relative weight of rider and machine(if someone disagrees, I would appreciate an explanation). In particular, there are thousands of expert motorcycle riders in the world who can ride a motorcycle no hands perfectly well, at least in a straight line. For example, it is traditional for GP motorcycle racers to ride no handes on their victory laps, and even to stand on the pegs. I have seen such riders initiate a turn while standing on the pegs, though they grab on to the bars shortly thereafter. However, it must be noted that riding no hands in a straight line already requires the ability to turn no hands, since keeping a straight line requires constant adjustment of trajectory. This proves that the statement that a motorcycle cannot be turned by rider lean alone is false. ilan 16:01, 12 January 2007 (UTC)

No sweat. It is an interesting thought experiment, and I don't doubt that it happens. I just wish we had a source, and I would like to know what conditions are necessary. As for motorcycles, I tried to express in the article that it is a matter of degree that varies with relative weight (quantitative, not qualitative). Hence the terms "heavy bikes (many motorcycles)" and "ineffective at initiating turns." I imagine that 500cc GP bikes are quite light. -AndrewDressel 15:35, 12 January 2007 (UTC)

Thanks. I've changed my comment above to be slightly more precise. I've looked at your website and see that you are teaching Mechanics. You could try to study my experiment, assuming you have nothing better to do :) Otherwise, it is true that 500cc GP bikes are (were?) light, however, there are still no hands victory laps with the heavier Moto GP 4-strokes, whose weight (up to 350lbs) approaches those of standard street bikes, and keeping in mind that GP riders typically weigh less than the average motorcycle rider (they all had to move up from the 125cc class), the conclusion is that rider/vehicle weight ratio for GP racers is probably not very different from average rider and motorcycle. ilan 16:23, 12 January 2007 (UTC)

Perhaps, in addition to defining heavy and light motorcycles, we need to define turning. I don't know what the course looks like, but the issue may be that negotiating a victory lap no-hands is very different from turning onto a side street, avoiding a pothole, etc. -AndrewDressel 18:02, 12 January 2007 (UTC)

By the way, here are some more things to consider, which, at least to me, show that a precise understanding of the physical phenomenon is quite difficult: A. There is no mathematical theory of the bicycle because it is a non-holonomic system. As far as I know, there has been no conceptual advance since the publication of the book "Theorie der Kreisels" by Klein and Sommerfeld about 100 years ago. Ten years ago, I went to a talk by Jerrold Marsden of Caltech, where he modeled simpler objects (I think it was a snake-board) but he said that his methods could not deal with the bicycle at all. ilan 16:23, 12 January 2007 (UTC)

I believe you are mistaken to say that "there is no mathematical theory of the bicycle". Even though the non-holonomic constraint makes it complicated, there have recently been some excellent advances. For a comprehensive state of the field, read "Linearized dynamics equations for the balance and steer of a bicycle: a benchmark and review" By Meijaard, Papadopoulos, Ruina, and Schwab. (Online at http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/papers/BicyclePaper1Andyv38.pdf) Also check out JBike6, a software implementation of the benchmarked linearized equations of motion. (Online at http://www.tam.cornell.edu/~ad29/JBike6/index.htm). The benchmarking was performed with several fully-nonlinear models implemented in various mathematical packages, such as MATLAB, SPACAR, and AutoSim. The motorcycle industry has made similar gains. Check out FastBike at www.dinamoto.it -AndrewDressel 18:02, 12 January 2007 (UTC)

Thanks for this reference, I hadn't realised that some theoretical progress had been made. However, I should read the article carefully to make sure. I have some more comments about countersteering which actually could go into the main article (though they are based on personal experience). As I noted before, even riding in a straight line requires steering input. In particular, this explains what I consider to be a main difficulty in learning how to ride a bicycle, which is that the pedaling motion causes the bike to lean in the direction of the downwards pedal stroke and this has to be counteracted by turning the handlebars in the direction of that pedal stroke. I frankly have never heard anyone make this remark when teaching cycling (and I suspect that most persons instructing a child would say the reverse), I figured it out when I taught myself to ride backwards, that is, sitting on the handlebars and had to learn to turn the bars in the reverse direction from usual (with respect to my body) at each pedal stroke. One can observe this handlebar motion in any bicycle that is being pedaled, e.g., in television coverage of the Tour de France. Similarly, a motorcycle moving in a straight line will also require constant trajectory adjustment which is reflected in handlebar motion. Observation of handlebar movement can be used to determine whether actors in a movie or television series are actually driving their bicycle or motorcycle, or simply being towed on with the vehicle resting on a trailer (as is often done to appease insurance companies). In particular, I doubt Erik Estrada ever actually rode a motorcycle on the TV series C.H.I.P.S. and you can determine exactly which scenes in the movie Breaking Away were actually shot on a moving bicycle. ilan 19:10, 12 January 2007 (UTC)

B. It is perfectly possible to ride a motorcycle which suffers from a speed wobble, that is, whose front wheel is constantly oscillating, including riding such a bike no hands in a straight line. ilan 16:23, 12 January 2007 (UTC)

Continuing on the theme that things are hard to understand, I just remembered a case where a motorcycle is able to go in a straight line with no steering input and independently of rider body position. It concerns the person who makes his living by taking a large motorcycle, driving it at high speed, then getting off the bike and dragging himself by holding on to the back -- I think he has special metal-soled boots. I don't even know where to find a reference for this! ilan 16:34, 12 January 2007 (UTC)

These two examples, if anything, suggest a motorcycles' tendency to remain moving in a straight line despite outside, non-steering, input. -AndrewDressel 18:02, 12 January 2007 (UTC)

Sorry, but you've got me started on one of my rants, that is, everything I write in this paragraph is based on personal anectodal experience, though the opinions will be stated in extreme terms, as if I had the weight of actual scientific evidence to back it up (actually this applies to most of what I write). Anyway, my personal experience with motorcycles was limited to small (<= 400cc) bikes and to a medium (700cc) bike with 16 inch wheels, and my steering of these vehicles was done by the countersteering technique alone, that is, I used the handlebars exactly like a car steering wheel (with the initial countersteer) with no body weight input. Then one day I drove a friends 1000cc BMW with 18 inch wheels and very short stubby bars. I tried my usual countersteering method and nothing happened, no matter how hard I applied pressure to the bars. Since a turn was rapidly approaching, I had to do something, and finally managed to get it turned by leaning my body. I noted that I hardly used any pressure on the bars. This experience convinced me that countersteering alone is not always sufficient to turn a motorcycle (exactly the opposite remarks of what was written by another user above). Just to get a little more objective, I read in Keith Code's motorcycle book that the force necessary to countersteer a GP bike is quite high, so an estimate of this force, if it is greater than the possible force applied by the rider (as measured using weight machines), would corroborate my assertion. ilan 16:58, 12 January 2007 (UTC)

I know what you mean about the frustration of using personal experience in Wikipedia. I've learned to use mine as a guide for finding citable references. For example, I know from personal experience that a long steering boom, such as the one on my Burley Canto recumbent, will overwhelm other self-stabilizing effects, but I cannot find a source, and so I've had to remove it from the Bicycle and motorcycle dynamics article. -AndrewDressel 18:02, 12 January 2007 (UTC)

[edit] Possible inter-Wiki Link

This technique is also used in 4 wheel motorsport but is termed "Scandinavian flick". Perhaps a link to the Wiki article would be relevant? 203.46.95.243 00:55, 13 February 2007 (UTC)

The only thing in common between the two is the momentary turn in the opposite direction. It doesn't appear to be for the same reason or work in the same way. Is it ever refered to by the same name? Otherwise, I'd say a link would not be relevant. -AndrewDressel 05:03, 13 February 2007 (UTC)

Hello Andrew. I've mentioned in the "Scandinavian Flick" page that perhaps it should be mentioned or merged into the "Opposite Lock" page. I have had the term "Scandinavian Flick" used by a motorcycle instructor trying to explain the countersteering concept to me, as I do 4-wheel motorsport, but I can see your point: "Opposite Lock" page link is much more appropriate here. Thanks for the suggestion. 203.46.95.243 01:37, 19 February 2007 (UTC)

[edit] Fascinating bit of OR

This article is clear, lucid, well referenced, and just plain wrong. While no-one denies that countersteering does work, it is not a necessary, and not even a normal, technique for steering a light bike at any speed, and, indeed, it becomes easier to steer without countersteering as speed increases. This is easily demonstrated by experiment.

Take any bicycle. Tie a piece of string from the seat post to the extremity of one handlebar, so that the steering can be straight or can turn to that side, but not even slightly to the other side. Ride the bike. If countersteering were necessary, the bike would be unridable. However, it is perfectly easy to ride - but you must eventually turn to the side where the string is. That turn is initiated without counter-steering, since counter-steering is not possible.

The normal technique for steering any light bicycle at more or less any speed above walking speed is to move the pelvis to one side while moving the shoulders to the other. This initiates a lean of the bicycle, which automatically turns into the lean. No countersteering is required. Simon Brooke 10:30, 20 February 2007 (UTC)

Just two questions:

1) Can you cite any reputable source for this claim?

2) In the expiriment you describe, how is the system center of mass leaned to the inside of the turn? Moving the hips one way and the sholders another merely lowers the center of mass. Wilson and Papadopoulos, in the 3rd edition of Bicycling Science state categorically that for the leftward lean necessary for a leftward turn "the support point must first move to the right of the system center of mass to create the lean." (Emphasis added by original authors). With the steering prevented from turning right, how can the support point move to the right? If I had to guess, I'd say that, especially at slow speeds, a very small turn is necessary, and a string tied between the seat and handle bar is insufficiently stiff to prevent such a small turn.

-AndrewDressel 15:08, 20 February 2007 (UTC)

Guess not. -AndrewDressel 18:05, 22 February 2007 (UTC)

Okay, since Simon Brooke appears to have gone missing, or cannot answer either of my two questions and won't say so, I would like to make it perfectly clear to anyone who might stumble upon this discussion. His claim above that this article (as it appears on March 1, 2007) as being "just plain wrong", is completely bogus. He will not be able to find a reputable source to back up his claim because one does not exist. His described experiment is completely refuted by the published work of David Jones (Physics Today, 1970) "the ridability of a bicycle depends crucially on the freedom of the front forks to swivel". Brooke's explanation completely misses the point of the need to move the combined center of mass and suggests a grave misunderstanding of basic physics and mechanics. -AndrewDressel 15:20, 1 March 2007 (UTC)