# Article On Countersteering

## Recommended Posts

Hey all,

I was talking to a physicist the other day who said he had intended to do his master's thesis on the physics of the bicycle and gave up because the math was just too complex. This was before modern computers and he was including the rider as a dynamic variable...duh.

Rider as a dynamic variable...the nerve.

ANYWAY...

@ mike

I don't get your point about the contact patch being flat and the cup being flat so the different radii don't apply....what? They are both flat and the analogy is pretty much perfect. The inside edge of the tire is a smaller radius circumference than the centerline. Just like the cup. Imagine gluing a non-conical tubular section between the cups to represent the upright position of the tire. The moment you lean over, you are rolling in a circle.

If the paper cup thing doesn't do it for you, then why do YOU think a wheel rolls in a circle when it leans over?

@ all

As for counter-steering vs gravity vs precession...

I believe it is the angular acceleration or lateral g that drives the "counter-steer" effect.

However, the question I find most interesting at the moment is whether something more than gravity affects how fast the bike flicks over so to speak.

Does a bike dropped from a static or standing still position in the paddock fall slower of faster than a bike flicked into a corner at speed? And why?

• Replies 73
• Created

#### Posted Images

OK, here's a request:

Is there any way we can get some drawings, or other media we can see (great if it had motion) to show how coutersteering works?

Anyone know where we can get this? Something that anyone could understand?

I know in Twist of the Wrist 1 page 78, Keith talks about it, and also says, "...I have heard varying explanations about what is happening during counter steering, but I have never heard 2 engineers agree totally on the physics of it." Maybe he has since this was written, but I'd like to see something that was in plain enough english that my 11 year old son would get it.

Best,

Cobie

##### Share on other sites

OK, here's a request:

Is there any way we can get some drawings, or other media we can see (great if it had motion) to show how coutersteering works?

Anyone know where we can get this? Something that anyone could understand?

I know in Twist of the Wrist 1 page 78, Keith talks about it, and also says, "...I have heard varying explanations about what is happening during counter steering, but I have never heard 2 engineers agree totally on the physics of it." Maybe he has since this was written, but I'd like to see something that was in plain enough english that my 11 year old son would get it.

Best,

Cobie

I wouldn't know where to begin to produce a video or animation, but think that these would be a great idea.

Instead, I'll try to summarise what I've said previously in as simple a way as I can.

Steering is simple.

A motorcycle/ bicycle will try to go to wherever the front wheel is pointing.

Period.

(Remove the words 'try to' if you want to be really simple.)

In longer words, point the front wheel to the left and the bike will try to go left, point the front wheel to the right and the bike will try to go right.

When we start to learn how to ride a bike, we learn very quickly that to turn a bike at any kind of reasonable speed we also need to lean it. We find this out through trial and error and it becomes instinctive (we don't need to think about it) very quickly. Our brains are clever enough to deal with all of this without our making any conscious effort to work out any complicated physics.

'Countersteering' is the method we use to lean the bike.

This is the instinctive bit (the bit we don't think about ... until we go to the cornering school or read Keith's books). Here we need a little understanding of physics (inertia).

Whilst moving in a straight line, when we turn the handlebars, the front wheel tries to go in that direction. However the rest of the bike doesn't know this and wants to continue in a straight line. Because the front wheel is going in one direction and the rest of the bike is going straight on, the bike leans over. Hold a broom handle upright against the floor and kick the bottom. It's effectively the same thing.

A video would be great here.

As the bike leans, the weight of the bike, combined with the steering geometry, forces the front wheel to point into the turn.

I struggle here to put this into words simply enough (as I probably don't understand the physics well enough).

I have mentioned some practical experiments earlier. These may or may not be very good or relevant, but I'll repeat them anyway.

• Whilst moving slowly forwards, turn the handlebars and note what happens. The bike will try to go in that direction. Do this at any speed and the same happens.
• Take a really tight turn at low speed (a U turn is perfect). You will be travelling very slowly, so any gyroscopic forces should be minimal. Note what happens. First you need to lean the bike and you do this by turning the bars away from the turn. Next you'll find that the bars will turn into the corner (you may even need to catch them to stop them from turning too far).
• Hold a bicycle by its seat and lean it over. Note what happens to the front wheel. It turns to the direction in which the bike is leaning, or into the turn.

Maybe the above aren't the best descriptions and I've no doubt the professor that Ulrich directed us to could do a better job. That was excellent reading.

Please guys, flame me all you like. I think I'm right, but don't we all

Hey Racer, no no plans to head to Tassie again any time soon. Just returned from a trip down the Great Ocean Road though, caravans and all

(NZ next Christmas, DEFINITELY!)

##### Share on other sites

Woody,

OK, that does help a bit. I've found a link that has some data, like to know what you guys think of it.

http://www.vsa.cape.com/~wayg/mrep/csteer.htm

Best,

Cobie

##### Share on other sites

Here's a 30 second video illustrating gyroscopic precession. It shows the bicycle wheel hanging from a string attached to one side of the axle and the wheel rotating around the string while spinning on the axle.

The force on the string (weight of the wheel) represents the countersteering force on the handlebar. Rotating around the string represents leaning caused by precession. It looks contradictory because the wheel is remaining vertical (although spinning and rotating), however if you view it from the right side (relative to the man in the video) at the beginning of the clip you will be in the same relative position of a rider pushing on the right handlebar and the wheel rotating around the string to the right represents the leaning to the right of the wheel. At the end of the clip you are viewing the wheel in the relative position of a rider and it's obviously leaning right with a right hand push. You can stop the video and play it frame by frame.

You may have to play it over several times to see what I'm talking about.

http://static.howstuffworks.com/mpeg/gyro.mpg

Above is the video

http://science.howstuffworks.com/gyroscope1.htm

Above is the link "how stuff works" I believe it explains in some detail the theory of countersteering.

##### Share on other sites

Here's a 30 second video illustrating gyroscopic precession...

I can't help but feel that the precession theory is fundamentally flawed as it is only considering the effect for one wheel, the front.

When you apply the precession theory to the front wheel only then it appears sound, but this is only part of the story as bicycles and motorcycles also have a rear wheel that is connected to the front via the frame and is fixed by the swing arm (so that it is unable to twist).

When the front wheel is turned, due to gyroscopic precession, the wheel will try to lean. I think we all agree that this is right, nobody has disputed this.

This 'lean' will also be transmitted via the frame to the rear wheel, which (applying the very same theory) will now try to twist. However, the wheel will be unable to twist because of the swing arm.

Because it will be unable to twist, the rear wheel will resist the precession effect of the front and will try to remain upright.

In short, the rear wheel, being fixed by the swing arm, will resist the lean induced by the front.

There will be some flex in the frame and I am sure that the bike turning will also negate the resistance a little, but I don't feel that these will be significant enough for precession to be considered anything other than having only a minor effect on the steering.

Happy New Year, by the way.

##### Share on other sites

How to measure the total effect of precession on steering a motorcycle?

How about a moto gp bike or superbike that has its front wheel 1 to 4" off the ground and the steering cranked to one side?

In this condition the exact effect of precession can be seen as very small.

Without the tire on the ground a motorcycle will generate very little steering effect.

Being an original squid (wheelie expert) I have played with this effect to control the bike for the last 25 years.

With the bike near balance the front wheel slows down quickly. Leaving corners under full power with the wheel just off the ground I have had the steering at the lock many times to the inside trying to get the bike to stand up. It does work, the faster the better.

It will only take a couple of times before you get the idea of how little steering effect precession produces with wheel off the ground and full lock steering.

I would liken this to the noBS bike and the real effect of "body steering" VS the idea of what it does.

Will

##### Share on other sites

The front wheel initiates the turn, the rear follows.

Notice also that in the video that if a leaning force is applied (in this case the string is applying the leaning force) that the wheel then turns IN THE DIRECTION OF THE LEANING FORCE.

I agree the back wheel resists turning and leaning, but it is overcome otherwise the bike could not turn at all. Well, it would be very difficult.

What if a bike could be built with wheels that had no mass at all? No precession would be present. I believe the bike could be steered much as it is steered when just rolling along at a slow walking speed (no countersteering). This thread is about countersteering and I believe that gyroscopic precession is the driving principal of countersteering. Most people believe that at speed, countersteering force turns the bike and progressively greater countersteering force turns the bike harder. I can prove this to my satisfaction every time I ride.

Hope you had a happy new year and Merry Christmas.

##### Share on other sites

How to measure the total effect of precession on steering a motorcycle?

How about a moto gp bike or superbike that has its front wheel 1 to 4" off the ground and the steering cranked to one side?

In this condition the exact effect of precession can be seen as very small.

That's for sure. A few other observations to support your point:

If you get lighter wheels for your bike you will find that it countersteers just as effectively, but with greater ease. If angular momentum were a primary force in initiating lean, lighter wheels should not be able to steer the bike as effectively.

If you observe someone countersteering quickly from behind, you will see that the bike rolls (leans) on an axis that is somewhere near or above the midpoint of the bike's height. Precession would create a torque at the axle and if precession were the primary cause of lean angle changes, the roll axis would be at the height of the axle.

Ski bikes reportedly countersteer. They don't have wheels; there is no precession involved.

##### Share on other sites

What if a bike could be built with wheels that had no mass at all? No precession would be present. I believe the bike could be steered much as it is steered when just rolling along at a slow walking speed (no countersteering). This thread is about countersteering and I believe that gyroscopic precession is the driving principal of countersteering. Most people believe that at speed, countersteering force turns the bike and progressively greater countersteering force turns the bike harder. I can prove this to my satisfaction every time I ride.

Hope you had a happy new year and Merry Christmas.

There is one datum that I just can't let go of; Single track vehicles Counter steer. There is no speed at which this is not true.

When going slowly you need to think of it in a different way though. Turn to the balance has been the best way I have found to explain it.

If the bike is leaning to the left and you want to go straight again you turn into the arc to stand it up. That is counter steering. also if the bike is falling to the left you steer into it , more left until you catch the balance or have to put a foot out.

Going slow you will find that the steering is often off center to one side or other, this condition is the new "center" around which another steering input would be measured. So if you are going 5mph and the steering is 20* off to the right as you are going around in a radius if you want to tighten it up you would steer left (19* from center) and if you wanted to stand it up you would turn right (21*off center).

My point is counter steering when going slow is real and occurs much of the time off the normal center of the handle bars making it a little harder to think with.

As for precession being the guiding force of counter steering I will disagree. I posted above the effect of precession when the front wheel is not in contact with the ground, VERY VERY LITTLE. Noticeable and usable to create minor steering inputs during wheelies.

As for timing there is other problem. The wheel must turn before precession is measurable. It is the by-product of changing the plane of the wheel not the driving force of the change. First the steering input then A precessional force, release the input and trail turns the wheel back into track with the rest of bike and another precessional force is measurable.

Other than being secondary the precession is trying to not let the wheel turn resisting the motion, not assisting it or much less causing it.

Trail is the force that self steers the bike, pointing the front wheel into the turn after the steering input is released.

##### Share on other sites

First the steering input then A precessional force, release the input and trail turns the wheel back into track with the rest of bike and another precessional force is measurable.

The above is a key point. If precession drove lean angle changes, then not only would the bike lean over when you countersteer, but when you stopped countersteering the bike would stand right back up when trail repositioned the wheel on the path of travel. That doesn't occur.

##### Share on other sites

You guys are correct about precession not being the dominant force if the facts you posted above are true, i.e.

1. Bikes countersteer quicker/better with lighter wheels

2. Turning the front wheel hard over when it's in the air has little or no effect on lean.

3. Single track (wheeless) vehicles countersteer.l

I may have to abandon my precession argument and admit I was wrong. Won't be the first time.

However, the "facts" cited above could be somewhat subjective so I'm not entirely giving up. I'd like to hear the official "guru" opinion.

As far as slow speed turning, it seems simple geometry. If you sight along the rake of the front wheel it intersects the ground at an point somewhere in front of the contact patch and remains in a plane with the rear wheel no matter which way or how much the front is turned. It's the contact patch that moves. When the bike is going straight ahead with no lean and the handlebars are turned to the right, that moves the contact patch to the left and the bike is now tending to fall to the right, the wheel is already turned to the right to allow centrifugal force to compensate and everything is happy. That's not countersteering. I went wobbling out of my driveway the other day demonstrating this to myself. When I'm going slow I steer by turning into the turns, the opposite of countersteering. Unless I'm just fooling myself.

##### Share on other sites

As far as slow speed turning, it seems simple geometry. If you sight along the rake of the front wheel it intersects the ground at an point somewhere in front of the contact patch and remains in a plane with the rear wheel no matter which way or how much the front is turned. It's the contact patch that moves. When the bike is going straight ahead with no lean and the handlebars are turned to the right, that moves the contact patch to the left and the bike is now tending to fall to the right, the wheel is already turned to the right to allow centrifugal force to compensate and everything is happy.

You are correct that in the case above when you turn the bars right the contact patch moves to the left. If the bike were not moving, it would indeed tip to the right. When the bike *is* moving, the front wheel veers to the right, as that's the direction it's pointing. If you don't do anything other than turn the bars, the bike would lean left. At low speeds, many riders are accustomed to initiating lean with body movement and then turning the bars into the arc. Whether you initiate lean with body movement or by consciously countersteering, once the bike is leaned, you do have to turn the bars (or allow them to turn) into the arc.

I went wobbling out of my driveway the other day demonstrating this to myself. When I'm going slow I steer by turning into the turns, the opposite of countersteering. Unless I'm just fooling myself.

I would guess that when you turned the bars, you also moved your upper body a little bit, since you expected the bike to lean in the direction the bars were turned. At such a low speed, your body weight would be sufficient to initiate lean.

Note that this is not the same thing as saying that countersteering does not work below a certain speed. If the wheels are rolling, countersteering will work. However, at low speeds, you can initiate lean with body weight shifts that would be ineffective at higher speeds.

To refer back to Will's example, if you have leaned the bike a little farther than you meant to in a low speed turn and find it about to fall to the inside of the turn, without putting a foot down, what would you do to save it?

##### Share on other sites

When I'm going slow I steer by turning into the turns, the opposite of countersteering. Unless I'm just fooling myself.

And that one aspect is why I don't like talking about steering using bicycles as examples, the steering inputs are soooo small and the rider outweighs the bike by so much it is easy to confuse the feedback.

Keep in mind that the only thing different is the speed and the lean angle, there is no dynamic geometric change in the bike with speed. It will still track exactly the same way at 3mph, 30mph,60mph,ect. Precession in the bike does change with speed, both of the wheels and the engine.

##### Share on other sites

First the steering input then A precessional force, release the input and trail turns the wheel back into track with the rest of bike and another precessional force is measurable.

The above is a key point. If precession drove lean angle changes, then not only would the bike lean over when you countersteer, but when you stopped countersteering the bike would stand right back up when trail repositioned the wheel on the path of travel. That doesn't occur.

Not true. When you stop applying a force the bike or wheel will tend to stabilize in the position it is in when the force is released. Otherwise you could say that if you countersteered through a 90 degree turn, when you quit countersteering the bike will un-countersteer back through the 90 degree turn. When I countersteer into a turn, I can coast through with hands off if I want.

You are correct that in the case above when you turn the bars right the contact patch moves to the left. If the bike were not moving, it would indeed tip to the right. When the bike *is* moving, the front wheel veers to the right, as that's the direction it's pointing. If you don't do anything other than turn the bars, the bike would lean left. At low speeds, many riders are accustomed to initiating lean with body movement and then turning the bars into the arc. Whether you initiate lean with body movement or by consciously countersteering, once the bike is leaned, you do have to turn the bars (or allow them to turn) into the arc.
Turning the bars right moves the contact patch left causing a lean to the right while at the same time the right hand turn leans the bike to the left via centrifugal force. Thus you have stability.
##### Share on other sites

Not true. When you stop applying a force the bike or wheel will tend to stabilize in the position it is in when the force is released. Otherwise you could say that if you countersteered through a 90 degree turn, when you quit countersteering the bike will un-countersteer back through the 90 degree turn. When I countersteer into a turn, I can coast through with hands off if I want.

Tim, do you believe that during an entire right hand turn your front wheel remains pointed to the left?

##### Share on other sites

Not true. When you stop applying a force the bike or wheel will tend to stabilize in the position it is in when the force is released. Otherwise you could say that if you countersteered through a 90 degree turn, when you quit countersteering the bike will un-countersteer back through the 90 degree turn. When I countersteer into a turn, I can coast through with hands off if I want.

Tim, do you believe that during an entire right hand turn your front wheel remains pointed to the left?

No, absolutely not. I have observed the wheel pointing in the direction of turn when countersteering was initiated. I never said that the wheel would be pointed to the left?

Do you not believe that applying a force to turn the front wheel to the left actually causes the bike to turn to the right?

An interesting phenomona is if you imagine a motorcycle in a stable turn on a curve thats banked at the opposite of the angle of lean so that the bike is perpindicular to the road surface. In this case the bike is turning following the curve, but at the same time it's not turning. The front wheel is in the same plane with the rest of the plane of the bike and the handlebars are not turned at all. The bike is actually tracking inside of an imaginary cone (or it could be a sphere) if the bank could be extended downward to a point of intersection. Anytime the back wheel is exactly following the track of the front wheel, there is no need for the handlebars to be turned at all. In fact, if the handlebars are turned the back wheel track does not follow the front, but follows a path to the inside (unless you're flat-tracking). I'm pretty sure I can prove this geometrically if challenged. Maybe this is a little off point, but it's part of the turning phenomina.

##### Share on other sites

No, absolutely not. I have observed the wheel pointing in the direction of turn when countersteering was initiated. I never said that the wheel would be pointed to the left?

Do you not believe that applying a force to turn the front wheel to the left actually causes the bike to turn to the right?

It sounds like we may now be on the same page about two things when entering a right turn:

1) Turning the front wheel left makes the bike lean right.

2) When you stop turning the front wheel to the left, it turns back to the right to follow the path of travel.

The only disagreement we have is whether precession makes the bike lean. I say not only is it not the primary force, it actually doesn't help the bike lean at all. Consider the following:

You know that if you hold a bicycle wheel in front of you by the axle ends and spin it forward, then push the right end of the axle forward the wheel will both turn left on a vertical axis and tip right on a horizontal axis. It's the classic demonstration of precession. If you then pull back on the right end of the axle, the reverse will happen; the wheel will turn right on a vertical axis and tip back left on a horizontal axis, returning to vertical.

With that in mind, consider countersteering. You're going straight and enter a right hander. You push forward on the right bar which turns the wheel left and the bike leans right. Once you stop pushing the bar, the wheel turns right to follow the path of travel. If precession were the driving force that leans the bike, the bike would stand back up. We both know that doesn't happen. And yet, precession doesn't work in only one direction or just when we want it to. Precession results whenever the wheel turns, but the resulting torque on the bike isn't enough to make it do much of anything. The wheel is held captive by a much larger mass.

It is the act of steering the tires out from under the bike to the left that makes the bike lean right.

##### Share on other sites

Just to make sure we are all on the same page, let me suggest that we say "push forward on the right bar" or the left one, to make sure we are all tracking.

As Andy pointed out, what happens when going very slow, motorcycle or bicycle, and one starts to fall/lean to the right? The correction is pushing forward on the left bar to catch the fall. In other words, countersteering was used to change the direction/lean of the bike.

I haven't yet been able to get my dad to answer this one thought!

##### Share on other sites

As Andy pointed out, what happens when going very slow, motorcycle or bicycle, and one starts to fall/lean to the right? The correction is pushing forward on the left bar to catch the fall. In other words, countersteering was used to change the direction/lean of the bike.

I think you need to think about that one again. Fall to the right and steer to the right by pushing on the left bar. Thats the opposite of countersteering. You were falling to the right so you steered farther into the right to correct, allbeit to make the bike fall back to the left. You're steering in the direction you want the bike to go. Countersteering is steering force applied in the opposite direction.

##### Share on other sites

The only disagreement we have is whether precession makes the bike lean. I say not only is it not the primary force, it actually doesn't help the bike lean at all. Consider the following:

You know that if you hold a bicycle wheel in front of you by the axle ends and spin it forward, then push the right end of the axle forward the wheel will both turn left on a vertical axis and tip right on a horizontal axis. It's the classic demonstration of precession. If you then pull back on the right end of the axle, the reverse will happen; the wheel will turn right on a vertical axis and tip back left on a horizontal axis, returning to vertical.

With that in mind, consider countersteering. You're going straight and enter a right hander. You push forward on the right bar which turns the wheel left and the bike leans right. Once you stop pushing the bar, the wheel turns right to follow the path of travel. If precession were the driving force that leans the bike, the bike would stand back up. We both know that doesn't happen. And yet, precession doesn't work in only one direction or just when we want it to. Precession results whenever the wheel turns, but the resulting torque on the bike isn't enough to make it do much of anything. The wheel is held captive by a much larger mass.

It is the act of steering the tires out from under the bike to the left that makes the bike lean right.

I totally disagree with that statement. When countersteering, the tire is not steered out from under the bike. Demonstrate for yourself. Going straight ahead at a moderate speed apply a slight countersteering force and observe the bike turning. Apply the force progressively harder and the bike will turn progressively quicker. You will not observe any "steering out from under" of the front wheel.

So, who are you going to trust? Me, or your own eyes?

##### Share on other sites

I totally disagree with that statement. When countersteering, the tire is not steered out from under the bike. Demonstrate for yourself. Going straight ahead at a moderate speed apply a slight countersteering force and observe the bike turning. Apply the force progressively harder and the bike will turn progressively quicker. You will not observe any "steering out from under" of the front wheel.

So, who are you going to trust? Me, or your own eyes?

Tim, I trust my own eyes. I still disagree with you. Have a look at the following video of a guy countersteering quickly to the right, as viewed from in front of the bike:

Video [1]

Watch the centerline of the bike and note how the front tire visibly swerves the the rider's left before the bike turns the the right. You will see that the front tire swerves at least four inches to the left of the original line of travel before the bike cuts right. The vantage point of the video does not let us see clearly how far out from under the bike's center of mass the wheels steer, but it will be around 12 inches.

Observing the phenomenon isn't simple, because the moment the bike leans, it begins to turn and you lose your vantage point. It's helpful to remember that the bike leans by having its tires steered out from under its center of mass, or roll axis if you like, not out of the line of travel. I make the distinction because the roll axis moves toward the inside of the arc as you lean the bike and this does make it hard to see the changing orientation of the contact patches and roll axis of the bike. Turning quickly is the only practical way to see this, as a great deal of lean angle change takes place before the bike peels off into the turn.

[1] The original link can be found on this page: Link. I don't agree with everything the author says, but he's mostly right.

##### Share on other sites

I think you need to think about that one again. Fall to the right and steer to the right by pushing on the left bar. Thats the opposite of countersteering. You were falling to the right so you steered farther into the right to correct, allbeit to make the bike fall back to the left. You're steering in the direction you want the bike to go. Countersteering is steering force applied in the opposite direction.

Tim, Cobie was making the point that to catch a fall to the right, you steer the front wheel farther to the right to make the bike stand up. That is definitely an example of countersteering.

If nobody has said it yet, countersteering is used merely to cause a lean angle change. Point the front wheel to the left, the bike changes lean angle to the right. That can be true whether the bike was vertical and you want to lean into a right hander or if the bike was leaned left and you want to bring it upright. It's countersteering either way.

##### Share on other sites

tz,

Good point about your video. In that case the steering force was hard enough to steer the wheel out from under the bike. So now explain how progressively harder steering force produces progressively greater countersteering turning even after the turn is initiated.

Tim, Cobie was making the point that to catch a fall to the right, you steer the front wheel farther to the right to make the bike stand up. That is definitely an example of countersteering.
I completely understand the first sentence. I totally disagree with the second sentence. In this case you wanted to steer to the right so you turned the wheel to the right. If countersteering you would have applied force to turn the wheel to the left.

You're trying to make the point that you countersteer at all speeds. I'm arguing that you don't countersteer at slow speeds, but that when the speeds increase then gyroscopic precession comes into play and countersteering rules. There's a transition zone also, such as parking lot speeds.

I'll be convinced that you're right and I'm wrong when I see if a bike countersteers at speed with no precession, such as with the counter-rotating rotors. The rotors would have to have the same angular momentum as the wheel to eliminate precession, as well as being in the same plane and on the same axis.

##### Share on other sites

And now all of this again leaves me with the question: Is my article acurate enough to keep it live on my site, or should i study and investigate some further? Next to the gsxr1000 k7 review this article is the second most viewed article on my site, so i would prefer to know if it is acurate enough to keep online.

Thanks to all of you that have given some more insight. I will take this furhter still and look deeper into it.

Best wishes to all of you for 2007!

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.