Talk:Countersteering/Archive 3

Archive 1

Archive 2

Archive 3

Include automatic countersteering in lead

I thought about the vehicles which relieves the driver from countersteering, and maybe there can be a sentence about this in the lead. We have kindof defined countersteering as being performed by the rider, which certainly is correct in most cases, but apparently not always.

I'm not sure if this is notable to have in the lead, but it is kindof short anyway. This goes for more three/four-wheelers only AFAIK, haven't seen any sources with two-wheelers doing this (do we have source for four-wheelers?).

Some multi-track vehicles use different approaches to countersteer implicitly to initiate a lean, and in these the driver just steers in the same direction as the turn.

Atlesn (talk) 21:22, 1 December 2014 (UTC)

Hello Atlesn. You are fast approaching my original point. There are two ways of looking at countersteer. You can focus on what the rider does or you can focus on what the vehicle does.In some vehicles where there is a direct relationship between driver input and front wheel/s steer angle both the driver and the vehicle do the same thing. In other situations this direct link does not exist and the rider does not directly apply the countersteer. In fact, this occurs on a conventional STV when the rider controls the vehicle " hands free",and there is a section in the Countersteer Article devoted to how this happens. In the further more recent examples the designers[ having observed the problems pointed out in the HURT report],choose to make the countersteer automatic and solely a vehicle condition while removing the need for the rider to apply the countersteer. But whatever or however... it is " countersteer" That's why the term "Automatic Countersteer" was coined [ not by me by the way], although I do use it extensively.

It is important to define "Automatic countersteer" as distinct from " manual countersteer". All forms of proper tilting vehicles are related right back to the pushbike. No designer will get anywhere without an in depth and intimate understanding of a pushbike and like the Wright brother observed, "there is a lack of understanding" We can now nail it down for them. PhillipCambering (talk) 02:03, 2 December 2014 (UTC)

I would not include this detail in the lede, and I have yet to see a reliable source for distinguishing "automatic countersteer" from " manual countersteer". -AndrewDressel (talk) 03:14, 2 December 2014 (UTC)

Phillip Back I had not noted the edits and I think its great progress. I have further edited the article in a way that makes some points clearer. I can provide scientific papers with regard the countersteer applied to the Carver which was an " option" originally but became standard fitment in production [ I will track it down and hopefully someone else can do the inserting] With regard the use of links to patents[ that I have not done ...yet,] let me say this. Normal countersteer was never patentable simply because it was a natural control phenomenon. However automatic countersteer was/is a patentable concept. My original application was the first example of Automatic Countersteer entered into "prior art". The CARVER system was the second example entered into "prior art". Now, because "wikepedia countersteering" concerns a technical field of significant importance I strongly suggest that patents are linked as defined by the Wikepedia Guidelines. To deny the use of the patents system as a valid source of technical information of great benefit to mankind is not acceptable. As I have said here, I am also editing the section on Patents and how they should be used because it was clearly biased. But I have no intention to expand the way patents can be used, but possibly this should be examined in the other place. Cheers PCambering (talk) 02:51, 2 December 2014 (UTC)

Patents as sources have been discussed before; see WP:PATENTS for a summary. You can cite a patent for certain kinds of facts, but they are, in many ways primary sources. If the only source for a fact is a patent, I'd give it very brief mention in the body, not the lead. If you want to give it greater attention than that, you've got to cite an independent, secondary source. If the source can't be found today, then let it go. In a half a year or a year something will turn up and then this article can give it greater attention.

While we wait, mankind will, somehow, carry on. --Dennis Bratland (talk) 03:27, 2 December 2014 (UTC)

Really? ok, I will go on holidays and hope for the best. PCambering (talk) 03:50, 2 December 2014 (UTC)

With regard to Andrews complaint that the term "Automatic Countersteer" has not been used in technical Journals see the following extract: I quote:

University of Bath

Ph.D., Active Control of Narrow Tilting Vehicle Dynamics

2010 – 2014

Developing and implementing an active roll stability control system for a prototype three-wheeled narrow tilting vehicle using an active steering system to generate automatic countersteering actions. The project led to a 40% reduction in load transfer, and the elimination of inside wheel lift-off, during a severe lane change manoeuvre.

So, indeed there is no reason to question the use of the term although I don't accept that the term was questionable as it uses normal language to describe something. The question of including a mention of Automatic Countersteer in the lead is now open for discussion.Cambering (talk) 23:09, 4 December 2014 (UTC)

Phillip back with clarification. The quote above is from Robertson who was the lead author of the Bath University paper. He uses the term " automatic countersteer" to refer to his work, but in his technical document this term was not used. This is a good example of my previous points where often a layman's description is preferred in general conversation because the technical work is loaded with complexity. Nevertheless the term is logical and its use in the Wikipedia is the preferred expression. I believe this is merely a matter of " common sense" being applied to the Wikipedia editing process.Cambering (talk) 00:03, 5 December 2014 (UTC)

A link to the paper would be handy. Where was it published? -AndrewDressel (talk) 13:48, 5 December 2014 (UTC)

Phillip here, This is James Robertson's LinkedIn page where he refers to his published documents and it is here he uses the quote I referred to above re " automatic countersteer". The most recent publication[2014] costs $36.Cambering (talk) 22:58, 6 December 2014 (UTC)

The two papers he lists that have been published do not mention the phrase "automatic countersteer" in their abstracts. Instead, he mentions the phrase in his description of his PhD dissertation, which might be a reliable source, if we had more details, but to which he does not provide a link. Thus, the link we have so far is merely to a self-published description of the work and not to a reliable source for distinguishing "automatic countersteer" from "manual countersteer". -AndrewDressel (talk) 15:26, 7 December 2014 (UTC)

Phillip here see:

DVC – The banking technology driving the CARVER vehicle class pdf, 2.4 MB – presentation at the 7th International Symposium on Advanced Vehicle Control, AVEC 2004, Arnhem (The Netherlands), August 2004

Contained in the document is the following description: 4.2 Improved STC The disadvantages of the standard STC can be best overcome by taking the balancing responsibility away from the driver and letting an automatic system take care of the front wheel steering to control the vehicle balancing. This has the following benefits: First it allows disconnecting the driver steering input from the front wheel, which makes it possible to present the driver with a ‘simple steer’ interface: To make a turn to the right, he simply has to steer to the right. The improved STC system will now take care of the initial steering input to the left which is required to tilt the vehicle body to the right in order to make a balanced motorcycle corner. Secondly, this ‘simple steer’ approach also removes the discontinuity when switching from ‘low speed lock’ to ‘balanced driving’ as mentioned in paragraph 3.2 STC.

Cambering (talk) 23:02, 16 December 2014 (UTC)

Phillip back with further comments The " Automatic system" is disclosed to "take care of the initial steering input to the left" when making a turn to the right. The "initial steering input" is already agreed here by editors[ in the Wikipedia article] to mean "countersteer" and so this description is of Automatic Countersteer by definition. The fact that the presenter does not use the specific term "countersteer" is not relevant because it is obvious.

Cambering (talk) 03:16, 17 December 2014 (UTC)

This is OT, but please try to format your posts a bit, all your posts up to now have had to be edited by me and others afterwards. Look at other posts to see how it's done and/or read here: Help:Wiki markup

Atlesn (talk) 23:10, 18 December 2014 (UTC)

looking at the lead it says "The rider's action of countersteering is sometimes referred to as giving a steering command"I propose this be removed because the action of countersteering is actually giving a leaning command.Other proposed changes include"Countersteering is used by single-track vehicle operators such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering the handlebars[ and so the front wheel],counter to the desired direction ("steer left to turn right").Countersteer is also used in multi-track leaning vehicles. Countersteer automatically applied,is used in some multi track leaning vehicles where the operators use a simple steer control style [ "steer left to turn left"][ insert link]To negotiate a turn successfully, the combined center of mass of the rider and the vehicle must first be leaned in the direction of the turn, and the front wheel/s steering briefly in the opposite direction causes that lean.[1] Cambering (talk) 16:12, 19 December 2014 (UTC)

The sources say steering command, can't just change it without another source. Atlesn (talk) 21:20, 19 December 2014 (UTC)

Countersteering: essential or beneficial?

• Reply to question from Arrivisto at User talk:Dennis Bratland#Countersteering: essential or beneficial?

The Hurt Report emphasized repeatedly and in no uncertain terms that ignorance of countersteering is a direct cause of motorcycle crashes. David Hough has at least 3 books that say the same thing, repeatedly. Every safety expert, motorcycle training course, and governemnt agency since then, and mostly likely before, going back to the Wright Brothers, has made it clear that consciously countersteering is not optional, it is essential. Yes, you can ride, but you cannot ride safely. Harry Hurt and David Hough and the others might agree with you that many riders are ignorant of countersteering, but they would present you with data which says that these untrained riders crash at a much higher rate than those who know how to coutnersteer, and that such riders contribute greatly to the fact that motorcycling is 30 or so times more dangerous than driving a car. I refer you to the sources listed in Motorcycle safety and related articles.

If you have quality sources which say that it isn't essential to consciously countersteer in order to ride a motorcycle safely, then please cite them. --Dennis Bratland (talk) 19:17, 16 June 2013 (UTC)

I 'd written: "In an ideal world, all motorcyclists would use countersteering. But many motorcyclists (particularly those who have not ridden off-road) have never heard of countersteering. Of course, one might argue that it is impossible to ride a bike at all without subconsciously countersteering, but I would still say (at the risk of entering into semantics) that countersteering is "beneficial" rather than "essential". To continue: It is axiomatic and universally accepted that a bike rider will be safer and more competent if he is aware of, and practises, counter steering, but even the most competent rider does not consciously think about it every bend. The article itself says (re bicycles): "..cyclists performing fast hill descents MAY also use conscious countersteering in order to initiate and manage the fast, precise turns necessary." Note the use of "may". The motorcycle section adds that counter steering is: "...is a part of the safe riding courses...". My point is that, as a conscious concept, countersteering is taught, not instinctive, and while the competent rider will be safer, that does not mean that uninformed riders will necessarily be unsafe or accident-prone. Arrivisto (talk) 19:40, 16 June 2013 (UTC)

So if I provide you with a list of citations which say that "uninformed riders, who are ignorant of countersteering, are unsafe", will that be satisfactory? I believe they are already listed in the articles I mentioned, but I can call them out one by one. And will you please cite the sources which say that countersteering training is nice but not necessary? -Dennis Bratland (talk) 20:11, 16 June 2013 (UTC)

Not for the first time, it must be observed that the use of a confrontational tone and thinly-veiled sarcasm is unhelpful and out of place in Wikipedia. Good faith and civility promotes reasoned argument and progress, not faux erudition. Arrivisto (talk) 21:05, 16 June 2013 (UTC)

I don't know what you're talking about. All I'm saying is I don't want to take the time to enumerate what all the sources say on this if doing so would be beside the point. As far as I'm concerned, all that matters here is whether the sources agree on this, or whether the sources tell us there is disagreement over whether countersteering is necessary. Here's some online examples:

• Hurt Report, p. 417: "Motorcycle riders in these accidents showed significant collision avoidance problems. Most riders would overbrake and skid the rear wheel, and underbrake the front wheel greatly reducing collision avoidance deceleration. The ability to countersteer and swerve was essentially absent." [1] This is probably the seminal statement on countersteering, which led to the push to train riders in the US.
• "If you don't know what makes a motorcycle lean, you'll never be able to swerve in a hurry." [2]
• "You need to understand countersteering before you think about starting up a motorcycle. ...understanding countersteering will save your life."[3]

Again, the sources agree that there are too many riders who don't understand countersteering, but they make clear that such riders are running on borrowed time. I can give you much more from offline sources. --Dennis Bratland (talk) 21:35, 16 June 2013 (UTC)

I would agree completely with Dennis on this and point further to Keith Code's No B.S. machine[4] as a demonstration of exactly why there is no such thing as steering without countersteering. — Brianhe (talk) 23:42, 16 June 2013 (UTC)

I don't disagree with either of you. But it's worth noting that while in the UK motorcycling training is now so rigorous that the number of learner riders is dropping significantly, some years ago training didn't exist and countersteering wasn't mentioned. Speaking anecdotally, I passed my bike test with an Isle of Man provisional licence, riding a 650cc BSA A10 (there was no capacity restriction for learners then). I hadn't had a single lesson, nor any preparation beyond watching the TT and reading the Highway Code. Some years later I started scrambling (moto-X) on an AJS Stormer, and only then were the scales removed from my eyes! Arrivisto (talk) 09:27, 18 June 2013 (UTC)

• Every safety expert, motorcycle training course, and governemnt agency since then, and mostly likely before, going back to the Wright Brothers - not quite that far back. During the 1960's, it seems that California Highway Patrol was reluctant to teach countersteering to it's motorcycle officers. In addition, in the written motorcycle exams at that time, one of the multiple choice questions was what happens to a motorcycle in a corner if the rider applies the brakes?. The correct answer was that the motorcycle straigtens up, as opposed to the radius of the turn decreases, which was one of the other choices. Apparently that exam assumed that the rider wouldn't know that countersteering could be used to avoid straightening up and maintain the lean angle while applying the brakes, which would have resulted in decreasing the radius of the turn. Rcgldr (talk) 02:18, 15 July 2013 (UTC)
  • That's excellent. Can you give the specifics on the source for this?

    It verifies that from the Wright Brothers[5][6] until the 1981 Hurt Report, there has been a tug-of-war over countersteering between those who knew bikes and those who only thought they knew them. Since 1981, physics has won. --Dennis Bratland (talk) 02:45, 15 July 2013 (UTC)

• As a global site, it's a concern that the word every in "Every safety expert, motorcycle training course, and governemnt agency", pertains only to the USA and Canada. The term Essential is not positive and not wholly true. The technique is highly recommended, but the word "essential" is not correct and may lead new riders to be disproportionately concerned with their own abilities which many training experts agree is a distraction from building safe skills and techniques. CarbonPepper (talk) 17:27, 22 December 2014 (UTC)

• The physics are the same globally. Please stop this if you don't have sources to cite. --Dennis Bratland (talk) 17:40, 22 December 2014 (UTC)
• Forgive me, "please stop this". Have I breached etiquette on contributing? I wasn't aware I needed your permission. Thank you for you message. As you own the page and the content, you are best placed to advise. Rather than citation, the evidence is in a lack of citation, how do I record this in my contributions please? The essential claim is borne of opinion and conjecture, none of the existing citations on the page state that it is essential. I've watched this page for years, have contributed via IP address edit and seen it drift in waves as different contributors get involved. It is not optimal, and blurs the concepts of Counter Steering (physics) and Deliberate Counter Steering (technique). CarbonPepper (talk) 18:14, 22 December 2014 (UTC)

If you have a source that says deliberate countersteering is not essential, or is a distraction from other more important riding techniques, then cite that source. If contrary opinions from experts exist, we should mention them. What we shouldn't do is fill article talk pages with endless bickering over the opinions of editors. The opinions of quality sources are what we need for articles. I think all those years of watching this page would have been better spent looking for sources to cite. You'll find that if you come prepared with sources you'll be taken much more seriously. --Dennis Bratland (talk) 19:39, 22 December 2014 (UTC)

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Negative steer angle through the whole corner in high speed (no drifting or wheel slippage)

When I explained countersteering (as described in the paragraph “How it works”) to my friend who is a motorcyclist, he replied that he did it subconsciously, but in higher speeds he didn't return the handlebars back and he kept countersteering through the whole corner. I, as a cyclist, found it very peculiar but after we looked at footage from a motorcycle race I had to agree that countersteering a whole corner is indeed a thing. On this image [7] you can clearly see that the handlebars are turned to the other side than usual and it doesn't look like the rear wheel was skidding either. I think this phenomenon should be also mentioned on this page. Do you know of any reliable articles that would explain it properly or at least confirm its existence? Michal Grňo (talk) 13:59, 17 December 2017 (UTC)

It seems to me that the bike in that image is in some unusual transition state, such as recovering from a rapid change in available friction, that the image does not contain enough information to explain because a quick survey on google of images of motorcycle racing doesn't find anything like it. Instead it is easy to find several images showing bikes at much more extreme lean angles and with front and rear tires so well aligned that it is impossible to tell what minute steer angles might exist: [8], [9], [10], and [11]

I don't know, off the top of my head, of a reliable article that confirms your friend's assertion, although I imagine that some combination of tire properties might make it possible. On the other hand, your friend's observation may not be reliable. Perhaps he is confusing the direction of torque applied at the handlebars with the angle between rear frame and the front fork. It is impossible to discern exactly what is going on in the image to which you linked, so I hesitate to draw any conclusions. -AndrewDressel (talk) 18:16, 17 December 2017 (UTC)

Okay, here is some better information. Cossalter, starting on page 125 of his Motorcycle Dynamics, examines "roll, steering and sideslip angles". He calculates roll and steer angles as functions of forward speed and turn radius for 3 different tire combinations on some "reference" motorcycle: front and rear tires have the same stiffnesses, front tire is stiffer and rear tire is softer, and front tire is softer and rear tire is stiffer. In "case 2: front tire stiffness (+10%), rear tire stiffness (-10%), which is most germain to this discussion, "at the same velocity and curvature radius, the steering angle necessary for equilibrium on a turn is notably smaller." The accompanying graph, however, only shows positive, in the direction of the turn, steer angles. It appears possible to interpolate from the graph what speed and curvature might be necessary to reduce the steer angle to zero or even into negative territory, but Cossalter notably did not bother. You can view his copyrighted image on Google Books. I interpret this omission to mean that negative steer angles are beyond the realm of normal motorcycle and even motorcycle racing behavior. -AndrewDressel (talk) 16:07, 24 December 2017 (UTC)

The steer angle is not negative with respect to the path that the front tire is moving. Once in a steady turn, the front tire points inwards of the path, due to slip angle. On a bike with a wider rear tire, as the bike leans over in a turn, the bike yaws inwards due to the contact patch moving further inwards of the center point on the rear tire, and in addition, the slip angle at the rear tire corresponds to a further inwards orientation of the frame of the bike. Rcgldr (talk) 00:45, 21 December 2017 (UTC)

A few of counterpoints:

• Cossalter claims (Motorcycle Dynamics page 52) that camber force can become more than necessary to maintain the turn and must be compensated for by negative slip angle, which would be towards the outside of the turn relative to the contact patch path.
• If the rear tire contact patch moves toward the center of the turn more than the front tire contact patch, because of a larger tire radius, that would make the rear frame yaw away from the direction of the turn, and that would require a greater steer angle in the direction of the turn to maintain a constant front tire slip angle.
• The rear tire cornering stiffness would have to be significantly less than the that of the front tire for it to produce enough understeering to require a steering angle opposite the direction of the turn.

-AndrewDressel (talk) 01:26, 21 December 2017 (UTC)

• Vittore Cossalter claims in chapter 3 of his book, also titled Motorcycle Dynamic (wrong book, probably Tony Foale's book), that there's always some amount of slip angle. My thought on this: camber force is related to lateral deformation of the contact patch, it's hard to see how deformation in response to a force would produce a greater force. The deformation is going to involve some amount of slip angle. -Rcgldr (talk) 04:09, 21 December 2017 (UTC)

• If negative slip angle does occur at the front tire, then that alone would explain true negative steering angle Rcgldr (talk) 20:37, 21 December 2017 (UTC)

• Do you have a page number for Cossalter's claim "that there's always some amount of slip angle." It is counter to what he claims in chapter 2 on page 52. -AndrewDressel (talk) 05:48, 21 December 2017 (UTC)

My fault, wrong book. I think it was Tony Foale's book (I borrowed the book a few years ago). The wiki article on Camber_thrust references both books, citing from Tony Foale's book that camber thrust can be the largest contributor (but not sole contributor) to camber thrust, and citing from Cossalter's book that in some cases camber thrust is the sole contributor. So Cossalter's book claims that in some cases, negative slip angle occurs? However, based on the initial discussion and the linked to image (looks like rear tire may be drifting), I assume that it's related to the cases where the rear tire has a positive slip angle. Rcgldr (talk) 17:29, 21 December 2017 (UTC)

"Since the lateral force generated must be exactly equal to that needed for equilibrium, the diminution of the lateral force is obtained through a negative sideslip angle." - Vittore Cossalter in Motorcycle Dynamics, page 52, 3rd paragraph.

• update - I found a reference from Tony Foale's web site: "because the camber angle of the bike is determined by the need to balance the machine for a given speed around a given corner, it is unlikely that in all cases will the camber thrust be of exactly the correct amount. e.g. Tyre size and compound will affect this force for a particular angle of lean. Therefore, it is necessary to have an additional method to correct the cornering force to that which we need to negotiate the turn in question. This is simply done by introducing a small slip angle by means of the handlebars. If the camber thrust generated is insufficient to match the cornering force needed, then we just turn the bars a bit more into the corner, or in other words introduce a positive slip angle." Tony_Foale_tyres.htm . Rcgldr (talk) 21:19, 21 December 2017 (UTC)

However, I have an issue with the concept of tires at a lean angle acting like cones. The "cone" effect could induce a small torque about the contact patch, but I don't see how this translates into a lateral force. The torque about a contact patch is very small and resisted by the contact patch of the "other" tire. A two cone vehicle, one cone in front of the other cone with parallel axis, and with uniform friction, tracks straight (or nearly so), with a lot of slippage. Rcgldr (talk) 21:19, 21 December 2017 (UTC)

Yeah, the cone analogy is not very helpful, but lateral force due purely to camber angle is real enough. -AndrewDressel (talk) 01:17, 22 December 2017 (UTC)

• If the rear yaws away from the direction of turn, then the front (and the entire bike frame) yaws inside of the direction of turn. -Rcgldr (talk) 04:09, 21 December 2017 (UTC)

• I don't believe I understand what you mean here. I use "yaw" to mean a rotation, not a displacement, and all parts of a rigid body, such as the rear frame of a bike, have exactly the same yaw angle. -AndrewDressel (talk) 05:48, 21 December 2017 (UTC)

So what did you mean that if the rear tire has a slip angle, that the rear frame would yaw away from the direction of the turn? Were you considering the case where the rear tire has a negative slip angle? Assuming a rear tire with positive slip angle, wouldn't that mean that the rear tire and frame yaw inwards of the direction of turn? Rcgldr (talk) 17:45, 21 December 2017 (UTC)

By "if the rear tire contact patch moves toward the center of the turn more than the front tire contact patch, because of a larger tire radius, that would make the rear frame yaw away from the direction of the turn, and that would require a greater steer angle in the direction of the turn to maintain a constant front tire slip angle," I mean that if the rear contact patch moves toward the center of the turn more than the front tire contact patch, that would cause the rear frame to rotate about a vertical axis (yaw) a small amount relative to the orientation it had before the lean and in a direction that is opposite to the direction of the turn and the lean. This is in addition to anything else going on, such as different slip angles or camber stiffnesses between the front and rear tires. -AndrewDressel (talk) 01:17, 22 December 2017 (UTC)

My point was that the rear contact patch does not move towards the center of the turn, but instead the rear of the bike moves outwards (the bike yaws inwards) due to a larger rear tire. Rcgldr (talk) 05:04, 22 December 2017 (UTC)

Let's just look at the kinematics for a second, and leave the stiffness for below. The lateral displacement of a tire due to camber will be the product of the camber angle in radians and the tire cross section radius. The contact patch of a bigger rear tire will move farther in the direction of a lean than the smaller front tire, and so contribute towards a yaw opposite the direction of the turn, and understeer. -AndrewDressel (talk) 12:33, 22 December 2017 (UTC)

Take the case of a rider hanging off while going straight (this is sometimes done while setting up for corner entry). The bike leans a bit to the "other" side, which offsets the rear contact patch more than the front, but the rider's inputs will line up the contact patches in order for the bike to continue tracking in a straight line. A similar thing happens when the bike is tracking along a curve. Rather than the rear contact patch moving inwards, it tracks a path based on rider inputs, lateral load, ..., and the end result is that the contact patch doesn't move inwards, but instead the rear of the bike moves outwards. Rcgldr (talk) 15:36, 22 December 2017 (UTC)

Well, in that case, I guess we're done here. -AndrewDressel (talk) 16:03, 22 December 2017 (UTC)

I lost an edit. What I left out is that the bike will yaw inwards or outwards, depending on whatever slip angle (positive, zero, negative) is needed by the rear tire to provide the required lateral force, combined with the offset of the contact patch from the rear tire's center line. Rcgldr (talk) 19:34, 22 December 2017 (UTC)

So you are saying that it depends on the tire. Good to know. -AndrewDressel (talk) 20:13, 22 December 2017 (UTC)

• Correct, it depends on the tire. I struck out some of my prior comments as your comment that the contact patch moves inwards as the bike is leaned is correct depending on other factors. The tire profile is a factor though, as lean angle changes, the contact patch area could get smaller (which would be an additional reason to hang off during turns), remain the same, or even bigger (old parabolic type profiles like Dunlop K81 used on British bikes).Rcgldr (talk) 20:13, 23 December 2017 (UTC)

• If the rear tire has the same relative stiffness as the front tire, and if the rear tire is wider, then it seems the absolute amount of lateral deformation will be greater at the rear, depending on weight distribution of the bike. The steering angle is never opposite the turn, but there may be cases where the steering is outwards relative to the bike frame, although still inwards with respect to the direction of the turn. -Rcgldr (talk) 04:09, 21 December 2017 (UTC)

• That is not how "stiffness" is measured and reported. If a spring or a tire deflects 2 inches or 2 degrees under 100 pounds of force, then their stiffnesses are 50 lb/in. and 50 lb/deg, respectively. The size of the spring or tire is not a factor. -AndrewDressel (talk) 05:48, 21 December 2017 (UTC)

I meant the same or similar construction resulting in the same strain (deformation / size) versus stress (lateral load) relationship. Similar to a longer spring that is otherwise the same as a shorter spring. Rcgldr (talk) 17:29, 21 December 2017 (UTC)

That doesn't help either. If two objects of the same shape have the same stiffness, then they will experience the same deformation under the same load. If one is bigger than the other, that is longer is the direction of the load and deformation, then it will experience LESS strain, because the same deformation is divided by a larger length. -AndrewDressel (talk) 01:17, 22 December 2017 (UTC)

Consider the case of two identical springs connected in series, the spring constant is divided by 2, and the same lateral load results in twice the distance of lateral deformation. A similar thing happens with a wider tire. Rcgldr (talk) 05:04, 22 December 2017 (UTC)

Ah ha. Now I get what you mean by "same relative stiffness". Yes, if doubling the size of a tire meant that its cornering stiffness decreases by half, then a wider rear tire would have a larger slip angle than the front and contribute to a yaw of the rear frame in the direction of the turn, an oversteer. The problem, however, is that I don't recall any suggestion that tire stiffness varies that way. In fact, in my testing of bicycle tires, different sizes of the same model with the same pressure and same vertical load tend to have higher absolute stiffness as they get bigger. Instead, the likely more important factor is inflation pressure. Larger tires under the same load usually have a lower inflation pressure, and I have seen tire stiffness decrease as pressure decreases. At the same time, however, circumferential tension in the casing is directly proportional to the internal pressure and to the tire diameter so the casing of a bigger tire can be at the same or higher tension even if the pressure is reduced. This may matter less in motorcycle tires, with much thicker carcases and lower pressures, but I don't know by how much. -AndrewDressel (talk) 12:33, 22 December 2017 (UTC)

• The key factor here is the frame's yaw angle corresponds to the rear tire slip angle. Since the discussion is about negative steer angle, then a rear tire with positive steer angle would correspond to the frame being yawed inwards of the path, perhaps enough that the steering is "outward" relative to the frame, but still "inwards" relative to path (assuming positive slip angle for the front tire as well).Rcgldr (talk) 20:19, 23 December 2017 (UTC)

On a somewhat related note, many bikes tend to straighten up unless some small amount of countersteering torque is applied to the handlebars in order to hold a lean angle. Rcgldr (talk) 00:45, 21 December 2017 (UTC)

Any bike in its range of forward speeds that produce self-stability will do this. -AndrewDressel (talk) 01:26, 21 December 2017 (UTC)

Motorcycle section - needs a fix, higher speeds reduce self-balancing

The last sentence in the motorcycle section intro includes this statement: "At higher speeds the self-balancing property of the bike gets stronger, and more force must be applied to the handlebars". Even though there's a reference, it's wrong and conflicts with Bicycle_and_motorcycle_dynamics#Lateral_motion_theory, specifically the eigenvalue section that shows as speed increases, a bike with infinitely thin tires approaches capsize mode, where it would fall inward at an extremely slow rate. The gyroscopic related reactions resist any change in steering or lean angle. The relatively slow rate of precession at the front tire at higher speeds acts opposes the self-correcting torques related to steering geometry (trail), acting as a damper at moderate speeds, which is helpful, but at high speeds, it becomes dominant and at high speeds, the rate of recovery to a vertical orientation is so slow that it's imperceptible to a rider. Rcgldr (talk) 07:03, 20 November 2018 (UTC)

I suggest replacing the statement with something like "at higher speeds, gyroscopic related reactions resist any change in steering input and/or lean angle and require increased effort by the rider to countersteer. Rcgldr (talk) 07:03, 20 November 2018 (UTC)

Perhaps just tweak the statement to "At higher speeds the self-balancing property of the bike gets stiffer, and a given input force applied to the handlebars produces smaller changes in lean angle." I hesitate to use "gyroscopic related reactions resist any change" as it is reminiscent of the magic attributed to wheels acting as gyroscopes that many of us have fought hard to eradicate from the discussion. Instead, the bike still responds but at a lesser rate, just as a stiffer spring does. FWIW, this is easy to show with JBike6, the MATLAB implementation of "a bike with infinitely thin and stiff tires." -AndrewDressel (talk) 15:03, 20 November 2018 (UTC)

The steering gets stiffer, and the rate of recovery (self-balancing property) to vertical becomes slower. At high speeds, the rate of recovery is so slow that it becomes imperceptible to a rider. So in the eigenvalue diagram that follows Bicycle_and_motorcycle_dynamics#Lateral_motion_theory which is credited to you, what is the cause for the transition from stable to slightly unstable between "weave" speed and "capsize" speed if it is not related to gyroscopic reactions? Rcgldr (talk) 21:49, 21 November 2018 (UTC)

I don't mean to be glib, but take a look down this rabbit hole and see if you can find a better answer than "a complex interplay of geometry and mass distribution." -AndrewDressel (talk) 02:11, 22 November 2018 (UTC)

I've read those articles before. Note that the eigenvalue plot for the TMS (two mass skate (no rotating wheels)) bike doesn't have a "capsize" speed, as it's always "stable", while the eivgenvalue plot for the standard bike with rotating wheels does have a "capsize" speed. In this article from TuDelft, the eigenvalue diagrams show a capsize speed (v_c) at v = 8 m/s or greater: bicycle dynamics pdf Rcgldr (talk) 09:01, 4 December 2018 (UTC)

And what do those authors conclude from this difference? -AndrewDressel (talk) 12:56, 4 December 2018 (UTC)

I never saw any conclusion about the difference. I'm pointing out that the article for a bike with rotating wheels shows a capsize speed, and the article for the TMS bike does not. Rcgldr (talk) 10:07, 5 December 2018 (UTC)

• Getting back to the main point of this talk section, the statement "At higher speeds the self-balancing property of the bike gets stronger", is misleading (if self-balancing is interpreted as tendency to return to a vertical orientation). Once a lean is established, then without rider inputs, as speed increases, the rate of recovery to vertical decreases, and at sufficiently high speed, it's so slow that it's imperceptible. As speed increases, a bike transitions from tending to return to vertical from a lean, to tending to hold the current lean angle. As noted in the article, as speed increases, the amount of countersteering effort required to change lean angle increases, but this is due to resistance to change in lean angle as speed increases, not due to a stronger self-balancing property. Rcgldr (talk) 10:07, 5 December 2018 (UTC)

So, what do you want the article to say, and what source would you cite to support that? -AndrewDressel (talk) 13:19, 5 December 2018 (UTC)

The TuDelft article, the part about eigenvalues, could be used as a source, since it shows a decrease in self-stability (less negative on the graph) as speed increases. It's already included in Bicycle_and_motorcycle_dynamics#Lateral_motion_theory. Paragraph "C" of speed and steering pdf . Also standard physics, torque equals rate of change in lean angle times angular momentum. Angular momentum increases linearly with speed, so the required steering torque required to produce the same rate of change in lean angle increases linearly with speed. Rcgldr (talk) 00:14, 6 December 2018 (UTC)

1. You didn't indicate what you want the article to say. It is difficult to evaluate a source if what it is supposed to support is not known. -AndrewDressel (talk) 01:20, 7 December 2018 (UTC)

2. In any case, the first sentence in paragraph "C" of speed and steering pdf is disqualifying:

Gyroscopic forces, primarily of the two wheels, but also other components whose axis of rotation is in the same direction as the wheel spindles, tend to resist any change in the angle of lean of the motorcycle.

This is simply not true. -AndrewDressel (talk) 01:20, 7 December 2018 (UTC)

So you're suggesting that there can be a change in the direction of an angular momentum vector without torque? ... and that the racing motorcycle designers that have the engine rotating "backwards" to reduce resistance to changes in lean angle are all wrong? Rcgldr (talk) 10:53, 7 December 2018 (UTC)

No, not at all, and neither of those two assertions have much to do with the crazy notion that "gyroscopic forces ... test to resist any change in the angle of lean of the motorcycle," which would imply that a bike would somehow resist falling over even if the steering were locked so long as the wheels or engine parts were spinning. Instead

First let’s dismiss one gyroscopic effect. When a bicycle with fixed straight-ahead steering falls there are reaction torques on the frame and handlebars from the precession of the spinning wheels. However, these torques are orthogonal to the axis of fall and, for a bicycle with steering locked straight ahead, are completely reacted by the moment from the lateral forces of the ground on the wheels. A bicycle with locked steering falls over when moving forward exactly as it does when not rolling: “any kind of gyroscopic stabilization is going to disappear” - Kooijman, Meijaard, Papadopoulos, Ruina, and Schwab

OK, without stating the cause, motorcycle riders and I have experienced the fact that at higher speeds, it takes much more countersteering effort to cause a change in lean angle. As an extreme case, there's a race at Daytona that uses a one of the straights with steeply banked turns at entry and exit of the straight. Upon entry onto the straight, the bikes are nearly horizontal, going close to 180 mph, and the riders state that they have to clamp their knees on the gas tank in order to generate a large countersteering torque on the handlebars to get the bikes "unleaned" back to vertical. Is this all to due with resistance to steering at the front tire? I've experience the same at around 100 mph, along with the fact that I no longer have to countersteer to hold a lean angle (at that speed, the bike doesn't appear to want to change lean angle, so I don't have to hold the lean angle with some countersteering effort that I need to use at lower speeds). Rcgldr (talk) 15:25, 7 December 2018 (UTC)

I would hesitate to say "all", because nothing on a bike is simple, but I would be surprised if it were not the or a major contributor. In the potentially over-simplified case, because the steer axis is not vertical, among many other issues, of treating the front wheel simply as a spinning disk, the rate of precession, which would be approximately the rate of lean angle change, in response to an applied steer torque is inversely proportional to the spin rate, which would be directly proportional to the speed of the vehicle. That precession is not the only thing going on in a full bike, of course. The roll inertia of the bike applies a roll torque to the front wheel in opposition to that precession, which in-turn causes it to precess about the steer axis, which causes the front wheel to out-track, which creates a roll torque on the bike, and so on, and so on.

In any case, when I plot resulting lean angle for a bike ten seconds after a constant steer torque is applied vs forward speed v, the relationship is not linear. Instead, the resulting lean angle approaches zero asymptotically, approximately proportionally to v^-1. If I run the same simulation for a bike with no spinning parts, the resulting lean angle increases with forward speed. -AndrewDressel (talk) 17:10, 7 December 2018 (UTC)

That would agree with the experience of other riders and myself. The question is what if the rider input is zero and the only steer torque is related to steering geometry (trail on a conventional bike) on a leaned bike, does the rate of recovery to vertical decrease as speed increases? Rcgldr (talk) 12:33, 14 December 2018 (UTC)

I do not have a good answer for that because both the benchmark bicycle paper and Sharps motorcycle paper show an unstable capsize mode. Thus, in these models, an uncontrolled bike will slowly continue to increase lean angle. I suspect that someone has published a more-detailed model which does not exhibit this behavior, but I haven't found it in a couple of quick looks.

Wouldn't that conflict with the statement, "At higher speeds the self-balancing property of the bike gets stronger"? If I recall correctly, the model with a capsize mode involved infinitely thin tires. For real tires, as a bike leans, the contact patches shift inwards with respect to the center of mass of the bike, which should result in some "outwards" torque, perhaps enough to prevent capsize mode or at least increase the speed at which capsize mode occurs at. Rcgldr (talk) 09:30, 19 December 2018 (UTC)

I changed the article back in November to read:

At higher speeds the self-balancing property of the bike gets stiffer, and a given input force applied to the handlebars produces smaller changes in lean angle.

Yes, I can find several papers that assert that introducing realistic tire properties stabilizes the capsize mode. For example Bulsink, Doria, van de Belt, and Koopman in their paper on The Effect of Tyre and Rider Properties on the Stability of a Bicycle in Advances in Mechanical Engineering 2015, Vol. 7(12) 1–19 state:

The Magic Formula tyre model (case 6) destabilizes the weave mode (weave speed increases to 9.3 m/s), but stabilizes the capsize mode.

I haven't found yet, however, someone who asserts or hypothesizes about which tire property is responsible for this stabilization. -AndrewDressel (talk) 17:38, 19 December 2018 (UTC)

Thanks for the help with this. Rcgldr (talk) 15:57, 22 December 2018 (UTC)

In fact, it is a well known principle in motorcycle racing that steering torque applied to the handlebars causes the spinning front wheel to apply a leaning torque to the rest of the bike and this can help a bike reach the desired lean angle sooner than the roll moment generated by gravity alone. Cossalter provides a sample calculation of this effect on page 295 of his Motorcycle Dynamics, which is also presented in the bicycle and motorcycle dynamics article. -AndrewDressel (talk) 13:31, 7 December 2018 (UTC)

3. The torque that changes lean angle is completely different from the steer torque applied to the handlebars. -AndrewDressel (talk) 01:20, 7 December 2018 (UTC)

Gyroscopic effects

Toy gyroscope modified to demonstrate lack of stability when precession is prevented

Toy gyroscope modified to demonstrate lack of stability when precession is prevented bottom side

A simplified look at bike roll rate with Euler's Equations for 3D rigid body motion:

The section on this ignores the rear tire's angular momentum based resistance to any change in lean angle. From my own experience on several motorcycles, and based on what I've read in motorcycle magazines, as speed increases, it takes more steering effort (torque on the handlebars) to cause a bike to lean (or to cause any change in lean angle). The overall gyroscopic effect seems to be that it opposes or dampens lean response, and at sufficiently high speed, a bike tends to hold a lean angle rather than tend to straighten up. Rcgldr (talk) 14:38, 21 May 2018 (UTC)

Hmmm. Here are a couple of thoughts:

1. The increased torque required at the handlebars as forward speed increases is well explained by the increased angular momentum of the front wheel.
2. Given that the rear wheel is mostly prevented from precessing by the moment generated by the pair of contact patches, it will end up leaning about the bike's roll axis about the same as it would if it were not spinning about its axle at all.
3. The loss of self-stability of an uncontrolled, simplified bike as its speed increases is predicted by the equations of motion and is thought to be due mostly to the decreased rate of precession of the front wheel, which decreases its tendency to steer in the direction of the lean.
4. The angular momentum of the rear wheel doesn't really have much to do with how countersteering works or the need for countersteering.

-AndrewDressel (talk) 00:46, 22 May 2018 (UTC)

As speed increases, so does the angular momentum of the front and rear wheels, and a change in lean angle corresponds to a greater change in angular momentum of the wheels as speed increases, which should require a greater torque impulse about the roll axis. Rcgldr (talk) 04:29, 22 May 2018 (UTC)

Nope, that is an oversimplification of the gyroscopic effect that yields an incorrect conclusion in this scenario. So long as the contact patches have enough friction to prevent precession, i.e. yaw of the rear frame, the rear wheel will lean due to whatever roll moments may be applied exactly as it would if it were not spinning at all. The front wheel, on the other hand, which is relatively free to precess about the nearly-vertical steering axis, does so, and that precession contributes, positively or negatively, to the stability of the bike and the feedback experienced by the rider at the handlebars. -AndrewDressel (talk) 01:43, 23 May 2018 (UTC)

For a typical 1 liter bike, total mass of the wheels and tires is about 10% of the total mass of bike and rider, this effect could be significant at high speeds. I agree that the decreased rate of precession at higher speed accounts for the decrease (or at least most of the decrease) in self-stability, which is a separate effect. Rcgldr (talk) 04:29, 22 May 2018 (UTC)

A more-complete interpretation of the gyroscopic effect on the rear wheel is that the moment generated by the lateral forces at the yawing contact patches causes a precession about the roll axis. A bike moving forward and rolling to the left would cause the rear wheel to precess to the left. On the front wheel, this contributes to self-stability. The reaction forces in the contact patches preventing this precession of the rear wheel, however, would create a moment to the right, and this would cause the rear wheel to precess by rolling to the left. The big question is the magnitude of all the forces and moments. Perhaps Cossalter has an example with relevant numbers. I left my copy in the office. -AndrewDressel (talk) 01:43, 23 May 2018 (UTC)

So at higher speed if the expected rate of precession along the roll axis of the rear tire is less than the rate of change in lean angle along the roll axis, is the rear tire resisting the greater rate of change in lean angle? Rcgldr (talk) 02:02, 23 May 2018 (UTC)

That exceeds the capacity of my back-of-an-envelope analysis. If you want to try some numbers, JBike6 calculates the stability eigenvalues for an uncontrolled simplified bike for free. If you want a more-detailed analysis, including toroidal tires with finite stiffnesses, I don't know of a free tool. -AndrewDressel (talk) 11:48, 23 May 2018 (UTC)

As an analogy, if you hold a toy gyroscope and try to rotate it perpendicular to its axis, (and not allow precession) it's more difficult if the gyro is spinning than if it is not. Rcgldr (talk) 02:02, 23 May 2018 (UTC)

I've performed the simple version of that demonstration many times with a toy gyroscope and a little bit of coat-hanger wire. If the gyroscope is free to precess, it stays upright when spinning. If the wire prevents it from precessing, it flops over, to the naked eye, just as it does if it is not spinning. I don't have a good way to add a little yaw to the "contact patches" to see what that does. It is also in my office, and I'll post a picture once I get in. (Done, to the right) -AndrewDressel (talk) 11:48, 23 May 2018 (UTC)

I would have expected that the torque in the wire opposing horizontal precession would result in the gyroscope precessing "downwards", and at a slow rate if the gyro was spinning fast. Rcgldr (talk) 13:46, 24 May 2018 (UTC)

Nope. I try to show why with Euler's Equations in the little derivation to the right.

Cossalter, on pages 288-291 of his Motorcycle Dynamics, goes further and investigates the gyroscopic effect of the wheels "generated by yaw motion" during a turn. He calculates that the slight righting effect caused by the two spinning wheels in a 200 m (660 ft) radius turn at 40 m/s (89 mph) would require an additional 0.88° of roll to maintain equilibrium, on top of the "ideal" roll angle of 39.20°, so an additional 2.25% in a pretty aggressive turn, predicted without considering gyroscopic effects.

In the case of the racing motorcycle Honda_NSR500#1990-1998, Honda felt it was important enough to use a counter shaft to reduce / eliminate gyroscopic effect from the engine crankshaft. Other GP500 racing bikes used twin contra-rotating crankshafts. In the case of motogp racing motorcycles, the engines are run backwards to reduce the gyroscopic effect from the wheels motogp going backwards. Rcgldr (talk) 19:07, 25 May 2018 (UTC)

Well, at 10,000 rpm, there may be way more angular momentum to contend with. I am sure Cossalter works out an example, but now I am at the office and I left the book at home. Also, at elite racing levels, 2.25% can be a big issue, and turns are much more aggressive that 40°. -AndrewDressel (talk) 20:46, 25 May 2018 (UTC)

1 liter street bikes redline at 14,000 rpm, race bikes even higher. The point of spinning the engine backwards on moto gp bikes is to compensate for the gyroscopic effects of the wheels, in what is sometimes called "flickablity", how quickly lean angle can be changed. Rcgldr (talk) 01:35, 26 May 2018 (UTC)

Cossalter also calculates the contribution of engine angular momentum on page 293 and concludes for his example bike at 12,000 rpm that "the gyroscopic effect generated only by the engine is less than that of the wheels; the engine's contribution generally falls within the range of 5% to 15% of the gyroscopic effect generated by the wheels." In competitive sport, decreasing the gyroscopic effect by ~10% by "spinning the engine backwards" instead of increasing the gyroscopic effect by ~10% is apparently worth the effort. -AndrewDressel (talk) 15:57, 26 May 2018 (UTC)

As for the gyro, what I meant was the apparent resistance when holding a gyro and rotating it perpendicular to the axis (without allowing it to precess). You can feel a resistance if the gyro is spinning. Rcgldr (talk) 01:35, 26 May 2018 (UTC)

I cannot account for what anyone says they feel by hand. -AndrewDressel (talk) 15:57, 26 May 2018 (UTC)

I thought you had the toy gyroscope as shown in the picture, you could try this yourself. Spin the gyro, hold the gryo, and try to rotate the gyro perpendicular to it's axis, and not allow it to precess. I'm wondering if the effect is similar to Gyroscopic_exercise_tool where the resistance to movement increases as the speed increases, typically reaching some steady state where wrist motion and torque keep the internal ball spinning and rotating at the same speed). Rcgldr (talk) 02:21, 1 June 2018 (UTC)

Sure, I have the toy gyroscope in the pictures I posted, and so I know perfectly well how complicated and unexpected its motion can seem. What I meant by my comment above, however, is that human hands are a very poor tools for constraining motion, applying a known torque, or measuring a response. That's why I look for reliable sources, do the math, and experiment with instrumented equipment. -AndrewDressel (talk) 12:42, 1 June 2018 (UTC)

I see your point. I guess that just leaves the people that design racing motorcycles that consider gyroscopic forces to be an issue worth compensating for (backwards spinning engine, even if it costs a few horsepower). Rcgldr (talk) 13:36, 1 June 2018 (UTC)

unindent - minor note, motogp bikes redline at well over 16,000 rpm (making 260+ hp (electronics limit the power until around 150 mph to prevent wheelies)). The street version of the 2019 Ducati Panigale V4R redlines at around 16,000 rpm, making 221 hp at 15,250 rpm, or with the race exhaust, 234 hp at 15,500 rpm. Rcgldr (talk) 03:35, 2 July 2019 (UTC)

Deleted Bicycles section

I just deleted the old section on Bicycles because it was very misleading. It seemed to say that countersteering is a special turning technique that is useful in emergencies. I think the author didn't understand that *ALL* turns made using the handlebars are countersteering turns, whether you're aware of it or not. It's the only way to make a bicycle turn and maintain balance. (Well, actually you can also turn a bicycle "no hands" by shifting your weight - this is just another way to create the lean required to balance through a turn.) 81.229.78.249 (talk) 01:12, 9 October 2019 (UTC)