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Friday, July 16, 2010
THANK YOU TO ALL THE READERS OF BIKER-SPACE
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The Wave by Tom Ruttan A nice read for all Motorcyclists
To get the weekend off to a great start we found this wonderful and wanted to share it with the readers of Biker-Space. After you have read this article let's start waving a little bit more too each other because on the road on two's all we got is each other. Cars don't care or like us. So I'm waving now. Ride safe. Enjoy
The bike's passenger seat swept up just enough that I could see over my father's shoulders. That seat was my throne. My dad and I traveled many backroads, searching for the ones we had never found before. Traveling these roads just to see where they went. Never in a rush. Just be home for supper.
I remember wandering down a back road with my father, sitting on my throne watching the trees whiz by, feeling the rumble of our bike beneath us like a contented giant cat. A motorcycle came over a hill toward us and as it went by, my father threw up his gloved clutch hand and gave a little wave. The other biker waved back with the same friendly swing of his left wrist.
I tapped my father on his shoulder, which was our signal that I wanted to say something. He cocked his helmeted ear back slightly while keeping his eyes ahead.
I yelled, "Do we know him?" 'What?" he shouted. "You waved to him. Who was it?" "I don't know. Just another guy on a bike. So I waved." "How come?" "You just do. It's important."
Later, when we had stopped for chocolate ice cream, I asked why it was important to wave to other bikers. My father tried to explain how the wave demonstrated comradeship and a mutual understanding of what it was to enjoy riding a motorcycle. He looked for the words to describe how almost all bikers struggled with the same things like cold, rain, heat, car drivers who did not see them, but how riding remained an almost pure pleasure.
I was young then and I am not sure that I really understood what he was trying to get across, but it was a beginning. Afterward, I always waved along with my father when we passed other bikers.
I remember one cold October morning when the clouds were heavy and dark, giving us another clue that winter was riding in from just over the horizon. My father and I were warm inside our car as we headed to a friend's home. Rounding a comer, we saw a motorcycle parked on the shoulder of the road. Past the bike, we saw the rider walking through the ditch, scouring the long grasses crowned with a touch of frost. We pulled over and backed up to where the bike stood.
I asked Dad, "Who's that?" "Don't know," he replied. "But he seems to have lost something. Maybe we can give him a hand." We left the car and wandered through the tall grass of the ditch to the biker. He said that he had been pulling on his gloves as he rode and he had lost one. The three of us spent some time combing the ditch, but all we found were two empty cans and a plastic water bottle.
My father turned and headed back to our car and I followed him. He opened the trunk and threw the cans and the water bottle into a small cardboard box that we kept for garbage. He rummaged through various tools, oil containers and windshield washer fluid until he found an old crumpled pair of brown leather gloves. Dad straightened them out and handed them to me to hold. He continued looking until he located an old catalogue. I understood why my dad had grabbed the gloves. I had no idea what he was going to do with the catalogue. We headed back to the biker who was still walking the ditch.
My dad said, "Here's some gloves for you. And I brought you a catalogue as well." "Thanks," he replied. I really appreciate it." He reached into his hip pocket and withdrew a worn black wallet. "Let me give you some money for the gloves," he said as he slid some bills out. "No thanks," my dad replied as I handed the rider the gloves. "They're old and not worth anything anyway."
The biker smiled. "Thanks a lot." He pulled on the old gloves and then he unzipped his jacket. I watched as my father handed him the catalogue and the biker slipped it inside his coat. He jostled his jacket around to get the catalogue sitting high and centered under his coat and zipped it up. I remember nodding my head at the time, finally making sense of why my dad had given him the catalogue. It would keep him a bit warmer. After wishing the biker well, my father and I left him warming up his bike.
Two weeks later, the biker came to our home and returned my father's gloves. He had found our address on the catalogue. Neither my father nor the biker seemed to think that my father stopping at the side of the road for a stranger and giving him a pair of gloves, and that stranger making sure that the gloves were returned, were events at all out of the ordinary for people who rode motorcycles. For me, it was another subtle lesson.
It was spring the next year when I was sitting high on my throne, watching the farm fields slip by when I saw two bikes coming towards us. As they rumbled past, both my father and I waved, but the other bikers kept their sunglasses locked straight ahead and did not acknowledge us. I remember thinking that they must have seen us because our waves were too obvious to miss. Why hadn't they waved back? I thought all bikers waved to one another.
I patted my father on his shoulder and yelled, "How come they didn't wave to us?" "Don't know. Sometimes they don't." I remember feeling very puzzled. Why wouldn't someone wave back?
Later that summer, I turned 12 and learned how to ride a bike with a clutch. I spent many afternoons on a country laneway beside our home, kicking and kicking to start my father's '55 BSA. When it would finally sputter to a start, my concentration would grow to a sharp focus as I tried to let out the clutch slowly while marrying it with just enough throttle to bring me to a smooth takeoff. More often, I lurched and stumbled forward while trying to keep the front wheel straight and remember to pick my feet up. A few feet farther down the lane, I would sigh and begin kicking again.
A couple of years later, my older brother began road racing, and I became a racetrack rat. We spent many weekends wandering to several tracks in Ontario-Harewood, Mosport and eventually Shannonville. These were the early years of two-stroke domination, of Kawasaki
Eventually, I started to pursue interests other than the race track. I got my motorcycle licence and began wandering the backroads on my own. I found myself stopping along sideroads if I saw a rider sitting alone, just checking to see if I could be of help. And I continued to wave to each biker I saw.
But I remained confused as to why some riders never waved back. It left me with almost a feeling of rejection, as if I were reaching to shake someone's hand but they kept their arm hanging by their side. I began to canvass my friends about waving. I talked with people I met at bike events, asking what they thought. Most of the riders told me they waved to other motorcyclists and often initiated the friendly air handshake as they passed one another.
I did meet some riders, though, who told me that they did not wave to other riders because they felt that they were different from other bikers. They felt that they were "a breed apart." One guy told me in colourful language that he did not "wave to no wusses.'' He went on to say that his kind of bikers were tough, independent, and they did not require or want the help of anyone, whether they rode a bike or not.
I suspected that there were some people who bought a bike because they wanted to purchase an image of being tougher, more independent, a not-putting-up-with-anyone's-crap kind of person, but I did not think that this was typical of most riders. People buy bikes for different reasons. Some will be quick to tell you what make it is, how much they paid for it, or how fast it will go. Brand loyalty is going to be strong for some people whether they have a Harley, Ford, Sony, Nike or whatever. Some people want to buy an image and try to purchase another person's perception of them. But it can't be done. They hope that it can, but it can't.
Still, there is a group of people who ride bikes who truly are a "breed apart." They appreciate both the engineering and the artistry in the machines they ride. Their bikes become part of who they are and how they define themselves to themselves alone.
They don't care what other people think. They don't care if anyone knows how much they paid for their bike or how fast it will go. The bike means something to them that nothing else does. They ride for themselves and not for anyone else. They don't care whether anyone knows they have a bike. They may not be able to find words to describe what it means to ride, but they still know. They might not be able to explain what it means to feel the smooth acceleration and the strength beneath them. But they understand.
These are the riders who park their bikes, begin to walk away and then stop. They turn and took back. They see something when they look at their bikes that you might not. Something more complex, something that is almost secret, sensed rather than known. They see their passion. They see a part of themselves.
These are the riders who understand why they wave to other motorcyclists. They savour the wave. It symbolizes the connection between riders, and if they saw you and your bike on the side of the road, they would stop to help and might not ask your name. They understand what you are up against every time you take your bike on the road-the drivers that do not see you, the ones that cut you off or tailgate you, the potholes that hide in wait. The rain. The cold.
I have been shivering and sweating on a bike for more than 40 years. Most of the riders that pass give me a supportive wave. I love it when I see a younger rider on a "crotch rocket" scream past me and wave. New riders carrying on traditions.
And I will continue in my attempts to get every biker just a little closer to one another with a simple wave of my gloved clutch hand. And if they do not wave back when I extend my hand into the breeze as I pass them, I will smile a little more. They may be a little mistaken about just who is a "breed apart."
Thursday, July 15, 2010
What causes excessive tire wear
Excessive tire wear, and/or cupping, is a problem that most motorcyclists experience over time. Too often this is simply the result of failing to maintain proper tire pressure. However, this is far from a complete answer.
Cupping is a phenomena that is absolutely normal! Excessive cupping or excessive wear on one side of the tire as compared to the other is not.
There are at least seven causes of cupping and/or uneven wear in the front tire other than tire air pressure:
- Most roads are banked away from the center. Thus, if you ride vertical, the side of your tire closest to the center of the road wears more.
- Your tires 'scuff' when you force a speed change with them. The rear tire scuffs when you accelerate and when you brake (and every time you ride in a direction other than straight ahead.) Thus, it tends to have even 'cupping' as compared to the front tire (which scuffs when you brake but not when you accelerate.)
- While alignment is not usually a problem with motorcycles - it can be.
- Carrying an unevenly divided load (all your tools, jumper cable, etc.) in one saddlebag can result in your riding the bike other than vertical most of the time.
- Setting your TRAC (anti-dive) unequally can easily cause uneven tire wear.
- If one of your front shocks is defective you will experience uneven tire wear.
- Excessive use of the front brake will result in excessive cupping.
Wednesday, July 14, 2010
Steering Your REAR wheel does it more often than not - By: James R. Davis
"Steer" - To direct the course of.
When your motorcycle is stable in any course, whether in a straight line or in a curve, it is your rear wheel that is primarily responsible for maintaining that course and stability. Indeed, it's the job of your front wheel to DESTABILIZE the bike in order to change course. That is, your front wheel changes course, your rear wheel maintains it.
How is that possible? Well, I suppose it is easiest to think of in terms of influence. A spinning rear wheel provides gyroscopic stability to over 80% of your motorcycle (including yourself) because it is directly connected via its axle/swing-arm to the frame of the motorcycle. The front-end is only indirectly influenced by the spinning rear wheel.
[Rather a lot of attention has been given to this article in recent days because certain readers have maintained that if rear-wheel gyroscopic forces are so great it *should* be virtually impossible to 'flick' a fast moving bike into a lean as you enter a turn. Well, what the gyroscopic forces generated by a spinning rear wheel does is to try to maintain the direction of travel of the bike - and, just as with the front wheel, when a change in direction happens the wheel responds with 'precession' and leans at a 90 degree vector to that change. When you use counter-steering on the front of the bike to go, for example, to the right, you press the right grip forward. That causes the direction of travel of the bike to momentarily change to the LEFT which, in turn, is felt in both the front and rear wheels and the result is that both of them lean towards the RIGHT. The harder/faster the counter-steer effort is, the greater/faster that lean will occur. And THAT is why you can 'flick' the bike over onto a significant lean. (i.e., you are using gyroscopic precession.) Actually, that is only a small part of it - it's centrifugal force that accounts for the vast majority of counter-steering functionality.]
When a motorcycle is stable it will maintain its current course until an outside influence or steering input to the front-end results in destabilizing it and a new course is sought that will once again result in a stable motorcycle.
Proof that the rear wheel is directing the course of your motorcycle is easy to come by. Watch any motorcycle that is performing a 'wheelie'. Whether it is going in a straight line or it is in a curve, the motorcycle will continue that course even while the front wheel is off the ground.
The significance of this otherwise esoteric bit of insight should be to cause you to rethink about locking your brakes. For example, it should now no longer be a surprise that if (while going straight) you lock your rear brake and cause a skid that the motorcycle does not simply drag the rear tire along in a straight line - the majority of the motorcycle is deprived of the stabilizing effect of a spinning rear tire and it will try to fall over to one side or the other. On the other hand, if you lock your front brake (while going straight) and cause the front tire to begin to skid, there is every reason to believe that (so long as the rear wheel continues to spin with some speed and you leave the front wheel pointing straight ahead) the bike will continue to stand tall and track straight while you correct the problem (by releasing the front brake lever.)
Indeed, so long as there is meaningful speed and you are moving in a straight line, locking the front brake (for a brief time) is less dangerous than locking the rear brake. Obviously you do not want to lock either brake, ever, but it will happen. Further, we all know that we should not aggressively use either brake while the bike is leaned over in a curve. But now you should know that it is NEVER reasonable to aggressively use the rear brake, and why.
Tuesday, July 13, 2010
Counter-steering Not the least bit as simple as it feels--By: James R. Davis
Everyone who has driven a motorcycle has experienced it, the MSF classes mention (but don't explain) it, and motorcyclists discuss it all the time. But what is it, really? How does it work? Why does it work? All questions I will try to deal with in this discussion.
At very slow speeds we steer a motorcycle by turning the handlebar in the direction we wish to go. We can only do that at speeds of less than about 6 MPH. At any higher speed we do the exact opposite, whether we realize it or not. For example, assuming we want to turn to the right, we actually TRY to turn the handlebar left. This results in the front wheel leaning to the right and, as a result of the lean of the wheel, a turn to the right. This is counter-steering.
Why is it that we don't get confused regardless of our speed? Because we have learned that steering a motorcycle is an effortless chore. That attempt to turn the handlebar to the left FEELS like we are pushing the right grip rather than pulling on the left one. It feels like that because the harder we push it, the more the motorcycle turns to the right and, thus, it feels like the right grip is pushing back at you that much harder. In other words, we quickly learn to associate counter-steering feedback with the hand closest to the direction in which we wish to turn. Further, even a little bit of experience shows that counter-steering is essentially effortless while trying to turn the handlebar in the direction you want to go is impossible. Humans are relatively fast studies, after all.
It takes only a modest familiarity with a gyroscope to understand counter-steering - at least to understand how most people believe it starts to work. (They are generally WRONG, but I will explain their position nonetheless.) The phenomenon is called Gyroscopic Precession. This is what happens when a lateral force is applied to the axis of a spinning gyroscope. The spinning gyroscope translates the force vector ninety degrees off the direction of spin. Thus, if we try to turn our front wheel to the left, the force we use appears as a lateral force forward against the axle on the right side and this is translated into a force that tries to lean the wheel to the right. Similarly, trying to turn the wheel to the right results in the wheel trying to lean to the left.
But gyroscopic precession is not a necessary component of counter-steering. No matter how slight, if your front wheel deviates from a straight path your motorcycle will begin to lean in the opposite direction. It is entirely accurate to assume that even without gyroscopic precession, the act of steering the front wheel out from under the bike would start counter-steering in the opposite direction. This is a result of steering geometry - rake. You can observe it at a complete stop. Just turn your handlebars in one direction and you will see that your bike leans in the opposite direction as a result. [Please note that though gyroscopic precession is not a necessary component of counter-steering it facilitates it - makes it smoother - but does NOT cause it. In plain language - centrifugal force is what initiates counter-steering, not gyroscopics. Please see Centrifugal Force for a better understanding.]
Since your head and body are not directly coupled to a spinning wheel, they do not precess. Your body remains in-line with the bike's body.
In the case of a motorcycle, your handlebar input is immediately translated by gyroscopic precession into a lean in the opposite direction. Since your front wheel is attached to the bike's frame, the body of the bike also attempts to lean. It is the lean of the BIKE that overwhelms the handlebar effort and drags the front wheel over with it - gyroscopic precession merely facilitates the process and is essentially inconsequential in the outcome.
If, for example, you had a ski rather than a front wheel, the front would actually begin to turn in the direction of handlebar input (just like it does with a wheel instead of a ski) and body lean in the opposite direction would then overwhelm that ski making counter-steering still effective.
The ONLY WAY to turn a motorcycle that is moving faster than you can walk is via counter-steering it (if it only has two wheels). We have talked only about what starts that lean to take place. Indeed, all we have talked about is the directional change of the front wheel along with the simultaneous lean of the bike, both in the opposite direction signaled by handlebar input. So then what happens?
Before getting into what is actually somewhat complicated let me say that if you were to let go of your handlebars and provide no steering information whatever (or you were to get knocked off your motorcycle), after some wildly exciting swings from side to side your motorcycle would 'find' a straight course to travel in and would stabilize itself on that course, straight up! That's right, your motorcycle has a self-correcting design built into it - known as its Steering Geometry - that causes it to automatically compensate for all forms of leaning and speed changes and end up standing straight up, going in a straight line, whether you are on the bike or not - until it is traveling so slowly that it will fall down.
This diagram shows a typical motorcycle front-end. The handlebars are connected to the steering column, which is connected to the knee bone, which is... Oops, wrong discussion. The steering column (actually called the 'steering stem') does not connect to the knee bone, nor does it connect directly to your forks! Instead, it connects to what is known as the triple-tree (shown as D in the diagram.) This is merely where both forks are tied, along with the steering stem, to the bike's frame. You will notice that the triple-tree extends towards the front and that as a result the forks are offset forward some distance from the steering stem. (Notice the red diagonal lines marked C and C'.) This is known as the offset.
Now please notice that the forks are not pointing straight down from the triple-tree, but are instead at an angle. This angle is known as the rake. Were it not for that rake (and modest offset) the front tire would touch the ground at point A. (Most rake angles are approximately 30 degrees.)
What the rake does for you is profoundly important. For one thing, it causes any lean of the wheel to be translated into a turn of the wheel towards that lean. For another, it slows down your steering. That is, if you turn your handlebar 20 degrees at slow speed your course will change something less than 20 degrees. [At higher speeds you NEVER would turn your handlebars 20 degrees - the front wheel is always pointing virtually straight ahead.] Rake, in the case of higher speed turning then really does SLOW DOWN the realization of the turn. (We will see why soon.)
Looking at the diagram, imagine that instead of pointing to the right the wheel is pointing straight at you. (The body of the motorcycle remains pointing to the right.)
You will now recognize that the contact patch which was B before the wheel turned has now got to be near where C' is at. In other words, the fact that your wheel is on a rake results in the consumption of part of your steering input into a displacement of the contact patch of the wheel. (This is why steering is 'slower' - and the greater the rake, the slower it is. Note that 'slow steering' is NOT the same as 'under-steer'.)
Notice also that where the red diagonal line marked C' touches the tire is higher than where B touches the tire. This demonstrates that a consequence of turning is that the front-end of your motorcycle actually lowers based on rake geometry. The distance between where B and C (not C') touch the ground is called trail. (Trail, as you can see, is determined by rake angle, offset and tire radius.) Some motorcycles will have the hub of the front wheel either above or below the forks rather than directly in the middle of them. In effect, these placements are designed to reduce or increase the effect of the offset in order to increase or reduce trail.
The stability of your motorcycle at speed is a function of how long its trail is. However, have you ever noticed that the front wheel on bikes that have excessive rakes (and therefore long trail) have a tendency to flop over (at low speeds) when they are not aligned perfectly straight ahead? This is the phenomena that explains just one of the reasons why your wheel actually turns in the direction you want to go after it begins to lean in that direction. Any lean whatever of the wheel, because gravity tries to lower the front-end, receives an assist from gravity in its efforts to move the contact patch forward along the trail. Further, notice that the pivot axis of your forks is along C, not C' and that this is behind the bulk of the front-end. Thus, gravity plays an even bigger role in causing the wheel to turn than at first glance it would appear. (And now you see why you have steering dampers - so that a little lean doesn't result in a FAST tank-slapping fall of the wheel in the direction of the lean.)
But there is another, more powerful, reason that the lean is translated into a turn - Camber Thrust. Unlike automobile tires, your motorcycle rides on tires that are rounded instead of flat from side to side. When you are riding vertically your contact patch is right in the middle of the tire, at its farthest point from the hub of the wheel. When you are leaning you are riding on a part of the tire that is closer to the hub of the wheel. The farthest parts of the tire from the hub of the wheel are TURNING FASTER than any part closer to that hub. Thus, when you are leaning the outside edge of the contact patch is moving faster than is the inside edge.
Imagine taking two tapered drinking glasses and putting them together as in the next diagram. Does this not bear a striking resemblance to the profile of your tires when looking at them head on?
Now imagine placing one of those glasses on its side on the table and giving it a push. Note that the glass MUST move in a circle because the lip of the glass is moving faster than any other part of it. The same is true of your tires. This camber thrust forces your wheel to turn in response to a lean.
Thus, both the rake geometry and camber thrust conspire to cause a leaning front wheel to become a turn in the direction of the lean. Then, of course, the motorcycle body follows the wheel and it, too, leans in the direction of the turn.
So, now you know what counter-steering is, how it works, and why. What might just now be occurring to you is with all of these forces conspiring to cause the wheel to lean and then turn in the direction you want to go, what stops that wheel from going all the way to a stop every time a little counter-steer is used? And, as I earlier mentioned, how does a pilotless motorcycle automatically right itself?
The answer to both of those questions is centrifugal force and, again, rake geometry. For any given speed and lean combination there is only one diameter of a circle that can be maintained. This is a natural balance point at which gravity is trying to pull the bike down and centrifugal force is trying to stand it up, both with equal results. (If you have Excel on your system you might want to click on this link for a model that demonstrates this concept.)
If the speed is increased without a corresponding decrease in the diameter of the turn being made, centrifugal force will try to stand the bike more vertically - i.e., decreases the lean angle. This, in turn, decreases the camber thrust and the bike will, of its own accord, increase the diameter of the turn being made.
If the speed had been held constant but the bike attempts to shorten the diameter of the turn beyond that natural balance point then centrifugal forces are greater than gravity and it stands taller, again lengthening the diameter of the turn as described earlier.
Once your bike is stable in a curve (constant speed, constant lean and constant steering input) then it will stay that way until it receives some change in steering input. (i.e., you use some additional counter-steering or the road surface changes or the wind changes or you shift your weight in some way or you change speed.)
As soon as any form of steering input occurs the stability of the bike is diminished. Momentum, camber forces and rake geometry will then engage in mortal combat with each other which will, eventually, cause the motorcycle to find a way to straighten itself out. That momentum will try to keep the motorcycle going in a straight line is obvious, but it also works with traction in an interesting way. That is, because the front tire's contact patch has traction the momentum of the entire motorcycle is applied to the task of trying to 'scrub' the rubber off that tire. If the body of the motorcycle is aligned with the front tire (only possible if traveling in a straight line) then there is essentially no 'scrubbing' going on. But if the bike is not in perfect alignment with the front tire, then momentum will try to straighten the wheel by pushing against the edge of that contact patch which is on the outside of the curve. As the contact patch touches the ground somewhere near point B, and because that is significantly behind the pivot axis of the front-end (red-dashed line C), the wheel is forced to pivot away from the curve.
I believe you now see why if the bike were to become pilotless it would wildly gyrate for a few moments as all of these conflicting forces battled each other and the bike became stable by seeking a straight path and being vertical. Clever, these motorcycle front-end designers. No?
At very slow speeds we steer a motorcycle by turning the handlebar in the direction we wish to go. We can only do that at speeds of less than about 6 MPH. At any higher speed we do the exact opposite, whether we realize it or not. For example, assuming we want to turn to the right, we actually TRY to turn the handlebar left. This results in the front wheel leaning to the right and, as a result of the lean of the wheel, a turn to the right. This is counter-steering.
Why is it that we don't get confused regardless of our speed? Because we have learned that steering a motorcycle is an effortless chore. That attempt to turn the handlebar to the left FEELS like we are pushing the right grip rather than pulling on the left one. It feels like that because the harder we push it, the more the motorcycle turns to the right and, thus, it feels like the right grip is pushing back at you that much harder. In other words, we quickly learn to associate counter-steering feedback with the hand closest to the direction in which we wish to turn. Further, even a little bit of experience shows that counter-steering is essentially effortless while trying to turn the handlebar in the direction you want to go is impossible. Humans are relatively fast studies, after all.
It takes only a modest familiarity with a gyroscope to understand counter-steering - at least to understand how most people believe it starts to work. (They are generally WRONG, but I will explain their position nonetheless.) The phenomenon is called Gyroscopic Precession. This is what happens when a lateral force is applied to the axis of a spinning gyroscope. The spinning gyroscope translates the force vector ninety degrees off the direction of spin. Thus, if we try to turn our front wheel to the left, the force we use appears as a lateral force forward against the axle on the right side and this is translated into a force that tries to lean the wheel to the right. Similarly, trying to turn the wheel to the right results in the wheel trying to lean to the left.
But gyroscopic precession is not a necessary component of counter-steering. No matter how slight, if your front wheel deviates from a straight path your motorcycle will begin to lean in the opposite direction. It is entirely accurate to assume that even without gyroscopic precession, the act of steering the front wheel out from under the bike would start counter-steering in the opposite direction. This is a result of steering geometry - rake. You can observe it at a complete stop. Just turn your handlebars in one direction and you will see that your bike leans in the opposite direction as a result. [Please note that though gyroscopic precession is not a necessary component of counter-steering it facilitates it - makes it smoother - but does NOT cause it. In plain language - centrifugal force is what initiates counter-steering, not gyroscopics. Please see Centrifugal Force for a better understanding.]
Since your head and body are not directly coupled to a spinning wheel, they do not precess. Your body remains in-line with the bike's body.
In the case of a motorcycle, your handlebar input is immediately translated by gyroscopic precession into a lean in the opposite direction. Since your front wheel is attached to the bike's frame, the body of the bike also attempts to lean. It is the lean of the BIKE that overwhelms the handlebar effort and drags the front wheel over with it - gyroscopic precession merely facilitates the process and is essentially inconsequential in the outcome.
If, for example, you had a ski rather than a front wheel, the front would actually begin to turn in the direction of handlebar input (just like it does with a wheel instead of a ski) and body lean in the opposite direction would then overwhelm that ski making counter-steering still effective.
The ONLY WAY to turn a motorcycle that is moving faster than you can walk is via counter-steering it (if it only has two wheels). We have talked only about what starts that lean to take place. Indeed, all we have talked about is the directional change of the front wheel along with the simultaneous lean of the bike, both in the opposite direction signaled by handlebar input. So then what happens?
Before getting into what is actually somewhat complicated let me say that if you were to let go of your handlebars and provide no steering information whatever (or you were to get knocked off your motorcycle), after some wildly exciting swings from side to side your motorcycle would 'find' a straight course to travel in and would stabilize itself on that course, straight up! That's right, your motorcycle has a self-correcting design built into it - known as its Steering Geometry - that causes it to automatically compensate for all forms of leaning and speed changes and end up standing straight up, going in a straight line, whether you are on the bike or not - until it is traveling so slowly that it will fall down.
This diagram shows a typical motorcycle front-end. The handlebars are connected to the steering column, which is connected to the knee bone, which is... Oops, wrong discussion. The steering column (actually called the 'steering stem') does not connect to the knee bone, nor does it connect directly to your forks! Instead, it connects to what is known as the triple-tree (shown as D in the diagram.) This is merely where both forks are tied, along with the steering stem, to the bike's frame. You will notice that the triple-tree extends towards the front and that as a result the forks are offset forward some distance from the steering stem. (Notice the red diagonal lines marked C and C'.) This is known as the offset.
Now please notice that the forks are not pointing straight down from the triple-tree, but are instead at an angle. This angle is known as the rake. Were it not for that rake (and modest offset) the front tire would touch the ground at point A. (Most rake angles are approximately 30 degrees.)
What the rake does for you is profoundly important. For one thing, it causes any lean of the wheel to be translated into a turn of the wheel towards that lean. For another, it slows down your steering. That is, if you turn your handlebar 20 degrees at slow speed your course will change something less than 20 degrees. [At higher speeds you NEVER would turn your handlebars 20 degrees - the front wheel is always pointing virtually straight ahead.] Rake, in the case of higher speed turning then really does SLOW DOWN the realization of the turn. (We will see why soon.)
Looking at the diagram, imagine that instead of pointing to the right the wheel is pointing straight at you. (The body of the motorcycle remains pointing to the right.)
You will now recognize that the contact patch which was B before the wheel turned has now got to be near where C' is at. In other words, the fact that your wheel is on a rake results in the consumption of part of your steering input into a displacement of the contact patch of the wheel. (This is why steering is 'slower' - and the greater the rake, the slower it is. Note that 'slow steering' is NOT the same as 'under-steer'.)
Notice also that where the red diagonal line marked C' touches the tire is higher than where B touches the tire. This demonstrates that a consequence of turning is that the front-end of your motorcycle actually lowers based on rake geometry. The distance between where B and C (not C') touch the ground is called trail. (Trail, as you can see, is determined by rake angle, offset and tire radius.) Some motorcycles will have the hub of the front wheel either above or below the forks rather than directly in the middle of them. In effect, these placements are designed to reduce or increase the effect of the offset in order to increase or reduce trail.
The stability of your motorcycle at speed is a function of how long its trail is. However, have you ever noticed that the front wheel on bikes that have excessive rakes (and therefore long trail) have a tendency to flop over (at low speeds) when they are not aligned perfectly straight ahead? This is the phenomena that explains just one of the reasons why your wheel actually turns in the direction you want to go after it begins to lean in that direction. Any lean whatever of the wheel, because gravity tries to lower the front-end, receives an assist from gravity in its efforts to move the contact patch forward along the trail. Further, notice that the pivot axis of your forks is along C, not C' and that this is behind the bulk of the front-end. Thus, gravity plays an even bigger role in causing the wheel to turn than at first glance it would appear. (And now you see why you have steering dampers - so that a little lean doesn't result in a FAST tank-slapping fall of the wheel in the direction of the lean.)
But there is another, more powerful, reason that the lean is translated into a turn - Camber Thrust. Unlike automobile tires, your motorcycle rides on tires that are rounded instead of flat from side to side. When you are riding vertically your contact patch is right in the middle of the tire, at its farthest point from the hub of the wheel. When you are leaning you are riding on a part of the tire that is closer to the hub of the wheel. The farthest parts of the tire from the hub of the wheel are TURNING FASTER than any part closer to that hub. Thus, when you are leaning the outside edge of the contact patch is moving faster than is the inside edge.
Imagine taking two tapered drinking glasses and putting them together as in the next diagram. Does this not bear a striking resemblance to the profile of your tires when looking at them head on?
Now imagine placing one of those glasses on its side on the table and giving it a push. Note that the glass MUST move in a circle because the lip of the glass is moving faster than any other part of it. The same is true of your tires. This camber thrust forces your wheel to turn in response to a lean.
Thus, both the rake geometry and camber thrust conspire to cause a leaning front wheel to become a turn in the direction of the lean. Then, of course, the motorcycle body follows the wheel and it, too, leans in the direction of the turn.
So, now you know what counter-steering is, how it works, and why. What might just now be occurring to you is with all of these forces conspiring to cause the wheel to lean and then turn in the direction you want to go, what stops that wheel from going all the way to a stop every time a little counter-steer is used? And, as I earlier mentioned, how does a pilotless motorcycle automatically right itself?
The answer to both of those questions is centrifugal force and, again, rake geometry. For any given speed and lean combination there is only one diameter of a circle that can be maintained. This is a natural balance point at which gravity is trying to pull the bike down and centrifugal force is trying to stand it up, both with equal results. (If you have Excel on your system you might want to click on this link for a model that demonstrates this concept.)
If the speed is increased without a corresponding decrease in the diameter of the turn being made, centrifugal force will try to stand the bike more vertically - i.e., decreases the lean angle. This, in turn, decreases the camber thrust and the bike will, of its own accord, increase the diameter of the turn being made.
If the speed had been held constant but the bike attempts to shorten the diameter of the turn beyond that natural balance point then centrifugal forces are greater than gravity and it stands taller, again lengthening the diameter of the turn as described earlier.
Once your bike is stable in a curve (constant speed, constant lean and constant steering input) then it will stay that way until it receives some change in steering input. (i.e., you use some additional counter-steering or the road surface changes or the wind changes or you shift your weight in some way or you change speed.)
As soon as any form of steering input occurs the stability of the bike is diminished. Momentum, camber forces and rake geometry will then engage in mortal combat with each other which will, eventually, cause the motorcycle to find a way to straighten itself out. That momentum will try to keep the motorcycle going in a straight line is obvious, but it also works with traction in an interesting way. That is, because the front tire's contact patch has traction the momentum of the entire motorcycle is applied to the task of trying to 'scrub' the rubber off that tire. If the body of the motorcycle is aligned with the front tire (only possible if traveling in a straight line) then there is essentially no 'scrubbing' going on. But if the bike is not in perfect alignment with the front tire, then momentum will try to straighten the wheel by pushing against the edge of that contact patch which is on the outside of the curve. As the contact patch touches the ground somewhere near point B, and because that is significantly behind the pivot axis of the front-end (red-dashed line C), the wheel is forced to pivot away from the curve.
I believe you now see why if the bike were to become pilotless it would wildly gyrate for a few moments as all of these conflicting forces battled each other and the bike became stable by seeking a straight path and being vertical. Clever, these motorcycle front-end designers. No?
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