Why does a bike turn

[Old Guy]

Kind of surprised it's not there already...
One of the books I read when I got back into riding talked about "something like" having a bike with steering locked straight ahead. Sounds impossible to ride, so I need to see if I can find it.

That'd be Keith Code's "No BS Bike."

I mentioned earlier that you could really see the countersteer if the rider's on a line. That's very clear at about 3:00 on this video.

 

[MajBach]

Kind of surprised it's not there already...
One of the books I read when I got back into riding talked about "something like" having a bike with steering locked straight ahead. Sounds impossible to ride, so I need to see if I can find it.

I can recall reading this too. The observation was a locked steering head still allowed for turning but was exceedingly difficult. Perhaps it was from "Proficient Riding".

 

[Fred W]

Not only can you not steer a bike with a locked steering stem, you can't even keep it upright. What allows you to keep a two wheeler from just falling on its side is any time the weight shifts to one side you steer the front wheel towards that side and correct the lean. If you take your hands off the bars the front wheel does the turning automatically. That is how you can ride the No BS bike, because the wheel pivots on the steering axis on its own.

You can test these ideas with a bicycle, but better try riding with the steering locked on a grassy area because you won't be able to keep it up with body English for long.

 

[Old Guy]

Not only can you not steer a bike with a locked steering stem, you can't even keep it upright. What allows you to keep a two wheeler from just falling on its side is any time the weight shifts to one side you steer the front wheel towards that side and correct the lean. If you take your hands off the bars the front wheel does the turning automatically. That is how you can ride the No BS bike, because the wheel pivots on the steering axis on its own.
You can test these ideas with a bicycle, but better try riding with the steering locked on a grassy area because you won't be able to keep it up with body English for long.

Doh! I didn't catch that. No, a locked steering mechanism would be impossible to ride further than it takes to fall over

 

[wfooshee]

Gyroscopic procession... when a force is put on a rotating mass (gyro or in this case the front wheel) the result of the force is 90* in the direction of rotation. In other words... if you put a force on the handlebars (gently push the left bar forward) the force is put at the back of the wheel. The result is a force at the top of the wheel 90* later trying to push it over. Then the bike has to lean and turn to keep it from falling over...hence a turn. Any other pilots here? This should sound familiar...

Nope. Gyroscopic forces have nothing to do with two-wheeled riding or steering. I think that if gyroscopic forces even applied, then turning one way would be significantly easier than the other, more so the faster you were going.

Countersteering pulls the wheels out from under the bike, inducing lean. The rider then steers into the lean, turning the bike. Then he steers harder into the lean direction to bring the bike's wheels back under the center of gravity, removing the lean and riding straight ahead. Just like countersteering to start the turn, you steer into the turn to stop the turn. Everyone talks about countersteering, does it actually exist, yes it does, no it's just pushing a bar, whatever. nobody actually talks about the opposite, to "ultra-steer" to end the turn.

Same concept, other direction. Start the turn by taking the wheels out from under the bike, stop the turn by putting them back.

Two-wheeled vehicles stay upright because they are always falling, but the rider steers into the fall, keeping the wheels underneath it.

(Unicycles, on the other hand.... that's just black magic!)

 

[Old Guy]

Gyroscopic procession... when a force is put on a rotating mass (gyro or in this case the front wheel) the result of the force is 90* in the direction of rotation. In other words... if you put a force on the handlebars (gently push the left bar forward) the force is put at the back of the wheel. The result is a force at the top of the wheel 90* later trying to push it over. Then the bike has to lean and turn to keep it from falling over...hence a turn. Any other pilots here? This should sound familiar...

Nope. Gyroscopic forces have nothing to do with two-wheeled riding or steering. I think that if gyroscopic forces even applied, then turning one way would be significantly easier than the other, more so the faster you were going.

Countersteering pulls the wheels out from under the bike, inducing lean. The rider then steers into the lean, turning the bike. Then he steers harder into the lean direction to bring the bike's wheels back under the center of gravity, removing the lean and riding straight ahead. Just like countersteering to start the turn, you steer into the turn to stop the turn. Everyone talks about countersteering, does it actually exist, yes it does, no it's just pushing a bar, whatever. nobody actually talks about the opposite, to "ultra-steer" to end the turn.

Same concept, other direction. Start the turn by taking the wheels out from under the bike, stop the turn by putting them back.

Two-wheeled vehicles stay upright because they are always falling, but the rider steers into the fall, keeping the wheels underneath it.

(Unicycles, on the other hand.... that's just black magic!)

I've read that bicycles have been successfully ridden and turned on wheels as small as a half inch. How the heck they managed to mount the wheels is beyond me, but the purpose was to show how little the centrifugal force actually has to do with steering. I can't argue the point because I can't produce the documentation, but I do tend to agree with wfooshee that we're simply moving the point of contact of the front wheel with the ground to once side causing the bike to lean the other way. How many of us remember when sport bikes started coming with 16" wheels? Prior to that front wheels would be 18" at least. Then some clever soul discovered how much more quickly he could turn with smaller, lighter wheels. It would seem that if gyroscopic procession caused the turn, heavier wheels would be more effective.

Here's an experiment I've tried.

Ride slowly in a straight line and come to a complete stop with your feet still up. Balance a second or two with your feet on the pegs, then put your left foot down. I must turn the front wheel to the right to make the bike lean left to put my foot down .... at a complete stop.

 

[wfooshee]

Which way you turn the wheel while stopped has far less influence on which way the bike leans than your own body position. Indeed, because of trail, if the steering input while stopped and upright was the only factor in play, the bike would lean right when you steered right, as trail puts the tire's point of contact left of the bike's centerline when you steer right. That trail is what gives the front wheel a self-centering effect while riding, and its absence, or worse, its opposite, would make the bike unridable.

 

[Old Guy]

Which way you turn the wheel while stopped has far less influence on which way the bike leans than your own body position. Indeed, because of trail, if the steering input while stopped and upright was the only factor in play, the bike would lean right when you steered right, as trail puts the tire's point of contact left of the bike's centerline when you steer right. That trail is what gives the front wheel a self-centering effect while riding, and its absence, or worse, its opposite, would make the bike unridable.

I rode today and played with it some. If I steer right at a stop the bike falls left and vice versa. I don't think I'm leaning my body, but if it doesn't rain I'm going out again Saturday. I'll play with it some more.

 

[Guitardave]

He states on page 28 "...the outside edge of the contact patch has a larger circumference than the inside edge of the contact patch. "

He compares this to a Styrofoam cup laid on its side and pushed forward.

The cup will turn due to the smaller diameter of the base of the cup.

Yeah, that sounds wierd to me..... all except the part about the cup.

I understand why a styrofoam cup rolls in a circle BUT, a contact patch is a FOOT PRINT.

Put your bike on it's center stand and lift the front tire off the ground momentarily.

Smear some chocholate syrup, ketchup, dish soap, or water on the tire, then set the tire down on

a sheet of notebook paper to see it's foot-print or "contact patch".

Right?

A "contact patch" has nothing to do with circumference!

It's an oval shaped tire foot print on the ground.

Now, if Parks was talking about the circumference of that patch around the tire,

I would 100% DISagree with his statement.

The largest circumference of the tire measured at it's center point when the bike is 100% vertical

is LARGER than the circumference measured at any other point on the sidewall, such as the rim,

or an inch above the rim, etc.

So, I just don't get it.

I like the original poster, have no idea what Parks is talking about.

 

[Fred W]

Yeah, I don't agree with his conclusions, but what he is saying is that when the bike is leaned over, the side of the contact patch towards the lean has a smaller circumference around the wheel and the circumference increases across the patch in the direction opposite the lean, which is generally true. And he then extrapolates that this is what causes the bike to turn, like the conical shape cup does when rolled.

We know that this difference in circumference is actually true as you can measure the tread squirm and slippage across the contact patch. It's the rubber tread slippage across the contact patch that causes tires to wear. Even going in a straight line there is slippage between the inside and edges of the CP .

However, if that was what actually caused the bike to turn then all you would have to do would be to lean the bike without moving the front wheel on the steering stem axis, and we know experimentally that this just does not work to turn the bike. You can try it with a scale model of a bike. If you lock the steering stem in place in a straight ahead position, when you lean the bike it will just fall on its side. You have to be able to steer the front wheel into the turn once you establish some lean to keep it from flopping on its side, and it is that steering action that actually turns the bike.

 

[Eagle Six]

I rode today and played with it some. If I steer right at a stop the bike falls left and vice versa. I don't think I'm leaning my body, but if it doesn't rain I'm going out again Saturday. I'll play with it some more.

I think I'm missing the value of a static turn of the front wheel and the balance of the bike, as to the OP's topic, but I would think a static test is tough because there are other influencing such as the pressure on the bars to swing the steering head and the friction on the contact patch, and of course rider input. I would think if you could put the front tire on a lazy susan (with ball bearings) and got all the weight of the rider off the bike, and could some how apply pressure equally to both bars, one pushing forward and the other pulling rearward without tipping the balance, your results may very well be different.

When I come to a stop I don't have to change by bars or lean the bike, I just put my foot/feet down. Of course if I want to plant by left foot on the heal and stabilize the bike with some tilt, I can then lean the bike to my left side, but I haven't found it necessary to turn the bars. Maybe I am missing something. Anyway I'll be interested in your findings tomorrow.

 

[Old Guy]

I rode today and played with it some. If I steer right at a stop the bike falls left and vice versa. I don't think I'm leaning my body, but if it doesn't rain I'm going out again Saturday. I'll play with it some more.

I think I'm missing the value of a static turn of the front wheel and the balance of the bike, as to the OP's topic, but I would think a static test is tough because there are other influencing such as the pressure on the bars to swing the steering head and the friction on the contact patch, and of course rider input. I would think if you could put the front tire on a lazy susan (with ball bearings) and got all the weight of the rider off the bike, and could some how apply pressure equally to both bars, one pushing forward and the other pulling rearward without tipping the balance, your results may very well be different.

When I come to a stop I don't have to change by bars or lean the bike, I just put my foot/feet down. Of course if I want to plant by left foot on the heal and stabilize the bike with some tilt, I can then lean the bike to my left side, but I haven't found it necessary to turn the bars. Maybe I am missing something. Anyway I'll be interested in your findings tomorrow.

I've just heard a lot of talk over the years that countersteering only works over some specific mph -- usually 5 or 7. I can make my bike lean even sitting still by turning the wheel in the opposite direction. It's not what you or I would normally do, but it's just a demonstration that you can induce a lean by countersteering ... even while the wheels aren't turning. It's actually kind of clumsy.

You say you just put your feet down. Of course. I start putting my left foot down before I stop, but I find myself turning the bar slightly right to get it to lean left as I put my foot down. If I try to put my left foot down, and it doesn't lean left .... I fall down.

 

[Eagle Six]

I've just heard a lot of talk over the years that countersteering only works over some specific mph -- usually 5 or 7. I can make my bike lean even sitting still by turning the wheel in the opposite direction. It's not what you or I would normally do, but it's just a demonstration that you can induce a lean by countersteering ... even while the wheels aren't turning. It's actually kind of clumsy.

You say you just put your feet down. Of course. I start putting my left foot down before I stop, but I find myself turning the bar slightly right to get it to lean left as I put my foot down. If I try to put my left foot down, and it doesn't lean left .... I fall down.

I think I'm following you now. However, during a turn of the bars while the bike is static may be misleading. There is friction (resistance) at the ground level from the contact patch. This friction resist the much lesser resistance of the steering head bearings, so the bike wants to move to the right (if you are turning left) much like a jackknife trailer. Nonetheless, take that friction, resistance and pressure out and the center of gravity is going to be on the left side due to the rake and trail, positioning the contact patch to the right of the bikes centerline. Countersteering doesn't turn a bike through the curve, it is simply an expedient method to get the bike to lean, which counters the centrifugal force so the bike and rider can smoothly steer into the turn and follow a line through the curve. Countersteering is also used to expedite recovering from a turn by reducing the steer and lean. And, it is used, if necessary, to maintain the line in our turn, which we could refer to as positive/negative steering.

There may be times when my bike for whatever reason isn't exactly balance, so I my have to turn the bars left or right to establish stop balance, but most often this is not necessary......I just stop, left foot down. I guess we all can use different methods.

 

[Old Guy]

I've just heard a lot of talk over the years that countersteering only works over some specific mph -- usually 5 or 7. I can make my bike lean even sitting still by turning the wheel in the opposite direction. It's not what you or I would normally do, but it's just a demonstration that you can induce a lean by countersteering ... even while the wheels aren't turning. It's actually kind of clumsy.

You say you just put your feet down. Of course. I start putting my left foot down before I stop, but I find myself turning the bar slightly right to get it to lean left as I put my foot down. If I try to put my left foot down, and it doesn't lean left .... I fall down.

I think I'm following you now. However, during a turn of the bars while the bike is static may be misleading. There is friction (resistance) at the ground level from the contact patch. This friction resist the much lesser resistance of the steering head bearings, so the bike wants to move to the right (if you are turning left) much like a jackknife trailer. Nonetheless, take that friction, resistance and pressure out and the center of gravity is going to be on the left side due to the rake and trail, positioning the contact patch to the right of the bikes centerline. Countersteering doesn't turn a bike through the curve, it is simply an expedient method to get the bike to lean, which counters the centrifugal force so the bike and rider can smoothly steer into the turn and follow a line through the curve. Countersteering is also used to expedite recovering from a turn by reducing the steer and lean. And, it is used, if necessary, to maintain the line in our turn, which we could refer to as positive/negative steering.

There may be times when my bike for whatever reason isn't exactly balance, so I my have to turn the bars left or right to establish stop balance, but most often this is not necessary......I just stop, left foot down. I guess we all can use different methods.

Bolded portion of the quoted post is exactly what I think. While we say that we turn by countersteering, we actually lean by countersteering. We turn by leaning. We can make the bike lean with body positioning (as in the No BS bike mentioned somewhere above), but it's nowhere near as effective.

Just consider if you will, that if you always stop with your left foot down, you must make sure the bike leans a tiny bit to the left. If you just pull up and stop while the bike is standing upright, and it starts leaning to the right ...... I know ... I'm splittin' hairs. But I've noticed that when I'm stopping, I almost always come up to the place where I'm stopping and in the last second or two before coming to a stop. I flop the bike left with my left foot down by turning the bars right, and I may not be doing more than a couple of mph. I only mention this because I've seen so many times that countersteering doesn't work below 5 mph.

 

[wfooshee]

I tried the static steer this afternoon. Bike stopped, feet already down, front brake on.. When I steered right, the front of the bike moved visibly to the right. Since the wheel didn't move other than slippage during the steer, that means the C.G. of the bike went to the right of the centerline of the contact patches of the tires, which would make it fall to the right. It wasn't enough to overcome other factors, though, such as me leaning my body to the left. It's a fact, though, that the trail behaves as I described above... The bike's CG is shifted towards the direction steered, not opposite.

 

[Old Guy]

OK. You guys win.

What I have is probably a case of confirmation bias.

I still ride up to a stop and turn the wheel, and it leans the other way. But I can sit in my garage balanced the best I can, lift my feet and turn the wheel and it just sort of randomly goes where it wants. So I'm obviously providing minute input while riding up to a stop that makes it do just what I expect.

Thanks for you patience.

 

[Northwoods Snowman]

I have an engineering background so I enjoy these kinds of discussions, or maybe I went into engineering because I like these kinds of things, who knows? I find it really interesting the variety of ideas that come out and the difference of opinions. Some people have what I think is a pretty good grasp of things and other not so much (but think they do) so it can make for some interesting dialog! I've fallen into both camps myself. I've explained things to others and in turn have gotten schooled on things too. While I think I have a fairly good understanding of the mechanics and physics behind steering a motorcycle, putting it into words is a whole other story. I'll at least make an attempt to share my point of view (right or wrong) by addressing some of the points brought up in the thread so far, in no particular order other than the order in which I think of them.

First off, the gyroscopic effect. It has been stated that it plays a major part, and that it plays no part what so ever. I think the truth falls into the middle. The gyroscopic effect plays a primary roll in the stability of the bike; the faster you go the more stable it is. Try riding without any hands on the handle bars at 10 mph, and then try at 50. The bike can wander all over at 10 mph, but stays fairly true to line at 50 mph. Also look at stunts that super cross racers do; the one in particular where they kick the back of dirt bike out about 90 degrees and then bring it back straight before landing. They can do that by manipulating the gyroscopic effect (as mentioned before with the 90 degree reaction force bit). The gyroscopic effect does not cause a bike to turn (unless you're airborne), quite the opposite, it resists the change in direction (hence giving the bike straight line stability at speed and at a given lean angle when cornering). Another way to practically see this in the real world is to weave between the dotted lane marker lines. Try it at 30 mph and then at 60 mph. Try to keep the tire close to the lines so you're side to side distance traveled is about the same. You'll find it takes a lot more input from the rider to weave back and forth rapidly at 60 mph then it does at 30 mph. I've done this myself and it can be hard to do it quick enough (even on a light weight dirt bike) at speed do you don't overshoot a line.

The contact patch quote the OP posted has been throwing some people off and it took me a few reads to figure out what he was saying. A couple of people have correctly explained it but I'll put it in my own words that may or may not help someone. I think the missing key information is that the "circumference" is not the circumference of the contact patch; it's the circumference of the TIRE rotating about the axle. The contact patch is basically a little disc and as you lean the bike that disc becomes angled relative to the axle. The side of the contact patch closer to the center line of the tire (outside of the turn) has father to travel in one revolution of the wheel than the side of the contact patch that is closer to the axle (inside of the turn). Because they are physically locked together, this causes a torque that try to turn the wheel about the axis of the steering head. That said, I think this has almost no affect on the bike actually turning.

Now, it is my opinion that the steering of the bike is almost (like 98%) entirely based on the geometry of the front suspension: axle relative to the center line of the steering head, or in other words rake, trail, and offset. Here's a link to a site I found via a quick search on google that gives an explanation of the geometries. The shape of the tire also plays a roll in the geometry (like how the handling goes to pot when the sides of the front tire get cupped or flattened off). I'll try to explain. The geometry is all about gravity. When sitting up straight, the center line of the contact patch is in line vertically with the steering head axis so it is balanced and doesn't want to turn left or right until it is forcefully turned. Once it is turned the contact patch on the tire moves sideways away from the center line of the steering head because of the trail of the front wheel (see link above) and the wheel naturally wants to flop over to the side in the direction of the lean because the contact point of the tire creates a torque about the axis of the steering head. You can see this stationary too. Put the bike on the kick stand with the wheel straight. Is is easier to turn the handle bars to the left or to the right? Turning them to the left drops the bike closer to the ground whereas turning to the right lifts the bike up. Now you might ask why the front wheel doesn't just keep turning further and further on it's own when you're leaning around a corner, and that's because the centrifugal force counters gravity trying to pull the front wheel over in the direction of the turn; same reason you don't just fall over too. A properly designed front suspension geometry will be "neutral" meaning that at a equilibrium speed, lean angle, and turning radius of the road, the bike will maintain the turn without under or over steering on it's own. Motorcycle publications will talk about the rake angle and trail and talk about how quick a bike will "turn in" and this is what they're talking about. Generally a higher rake angle (more vertical) will be quicker to turn, but less stable at high speed where as a low rake angle (more horizontal) will be more stable at speed but not as nimble in the turns. When was the last time you saw a steering damper on a chopper!?

Now as far as counter steering goes, on a properly designed bike you ALWAYS counter steer; both to initiate a turn and to control it. The counter steer action initially turns the front wheel in the opposite direction that you want to travel to initiate the bike lean, and then as the bike leans the wheel will naturally turn into the direction of the turn without further input from the rider. As the rider wants to change the magnitude of the turn, you have to either initiate more lean or less lean by counter steering. As you're going around a corner, the bike rides in it's "neural" state. If you want to turn tighter, you need to lean more and to lean more you counter steer a little; that doesn't mean you "turn" to the right in a left hand turn, it just means you turn a little less left. You can try this by riding around a corner of your choice but keep your palms on the handle bars with open fits so you can only make corrections by pushing on one side or the other. Try to move from the inside of the lane to the outside and back. This really hit home with me when I was in high school tooling around on my dual sport. One day I was doing something that required me to pull my right hand off the throttle (can't remember what) but in order to keep riding I had to use my LEFT hand on the RIGHT handle bar to control the throttle. I was all over the road until I figured out that I had to push/pull in the opposite direction that I wanted to maintain control of the bike. I had been riding bicycles and dirt bikes for more than 10 years and I was doing everything by muscle memory without consciously realizing what I was doing to control my bike. It sounds like a lot of you guys are in the same boat I was. If you're really in for an adventure try crossing a hand over to the opposite handle bar, but be careful (and you didn't get the idea from me)!

I probably wanted to comment on something else too but now after writing all this I've forgotten, so I'll call it quits. I hope this helps someone.

 

[Eagle Six]

Wow, what a great write-up. I'm sure that took some time. Very well explained.

First off, the gyroscopic effect. It has been stated that it plays a major part, and that it plays no part what so ever. I think the truth falls into the middle. The gyroscopic effect plays a primary roll in the stability of the bike; the faster you go the more stable it is. Try riding without any hands on the handle bars at 10 mph, and then try at 50. The bike can wander all over at 10 mph, but stays fairly true to line at 50 mph. Also look at stunts that super cross racers do; the one in particular where they kick the back of dirt bike out about 90 degrees and then bring it back straight before landing. They can do that by manipulating the gyroscopic effect (as mentioned before with the 90 degree reaction force bit). The gyroscopic effect does not cause a bike to turn (unless you're airborne), quite the opposite, it resists the change in direction (hence giving the bike straight line stability at speed and at a given lean angle when cornering). Another way to practically see this in the real world is to weave between the dotted lane marker lines. Try it at 30 mph and then at 60 mph. Try to keep the tire close to the lines so you're side to side distance traveled is about the same. You'll find it takes a lot more input from the rider to weave back and forth rapidly at 60 mph then it does at 30 mph. I've done this myself and it can be hard to do it quick enough (even on a light weight dirt bike) at speed do you don't overshoot a line.

Great explanation, absolutely agree.

The contact patch quote the OP posted has been throwing some people off and it took me a few reads to figure out what he was saying. A couple of people have correctly explained it but I'll put it in my own words that may or may not help someone. I think the missing key information is that the "circumference" is not the circumference of the contact patch; it's the circumference of the TIRE rotating about the axle. The contact patch is basically a little disc and as you lean the bike that disc becomes angled relative to the axle. The side of the contact patch closer to the center line of the tire (outside of the turn) has father to travel in one revolution of the wheel than the side of the contact patch that is closer to the axle (inside of the turn). Because they are physically locked together, this causes a torque that try to turn the wheel about the axis of the steering head. That said, I think this has almost no affect on the bike actually turning.

This again is enlightening and explained much better than the quote from Total Control. I admit I didn't spend much time trying to figure what he meant. I would think the friction difference from the smaller circumference to the larger circumference and throughout the patch would play a larger part than the actual difference between the two.

Now as far as counter steering goes, on a properly designed bike you ALWAYS counter steer; both to initiate a turn and to control it. The counter steer action initially turns the front wheel in the opposite direction that you want to travel to initiate the bike lean, and then as the bike leans the wheel will naturally turn into the direction of the turn without further input from the rider. As the rider wants to change the magnitude of the turn, you have to either initiate more lean or less lean by counter steering. As you're going around a corner, the bike rides in it's "neural" state. If you want to turn tighter, you need to lean more and to lean more you counter steer a little; that doesn't mean you "turn" to the right in a left hand turn, it just means you turn a little less left. You can try this by riding around a corner of your choice but keep your palms on the handle bars with open fits so you can only make corrections by pushing on one side or the other. Try to move from the inside of the lane to the outside and back. This really hit home with me when I was in high school tooling around on my dual sport. One day I was doing something that required me to pull my right hand off the throttle (can't remember what) but in order to keep riding I had to use my LEFT hand on the RIGHT handle bar to control the throttle. I was all over the road until I figured out that I had to push/pull in the opposite direction that I wanted to maintain control of the bike. I had been riding bicycles and dirt bikes for more than 10 years and I was doing everything by muscle memory without consciously realizing what I was doing to control my bike. It sounds like a lot of you guys are in the same boat I was. If you're really in for an adventure try crossing a hand over to the opposite handle bar, but be careful (and you didn't get the idea from me)!

The biggest problem I see with counter steering, isn't counter steering, rather the term and how we explain it! We not only use it to initiate the turn and control the rate, we also use it to recover and prepare for the next turn. When we counter steer to turn left by turning the front wheel initially right, the bike turns right momentarily which creates the lean. We almost immediately relax the counter steer pressure and as you point out the geometry of the suspension allows the front wheel to align more to the left. That momentary slight turn to the right isn't noticeable in sweepers, or even tighter turns, but if we hang far out a bit late and flick the bike into the turn to get a delayed apex, that's when we get that rush feeling of the bike going from straight up to extreme lean almost as if the front came up and over, despite we have loaded the front suspension with braking and trying to hold that traction load with trail braking. At higher speeds it difficult to determine how much, if any, the front wheel is turned towards the turn after the counter steer, at least for me, I have my eyes way out ahead (maybe a video would show the actual difference of alignment). At slower parking lot speeds it is easier to see how extreme the front wheel can be in a tight turn, even to the locks, as centrifugal force and gravity balance in a tight turn with extreme lean, just as they are equal when we are riding straight up in a straight line.

I like these discussions on days I'm not riding, as it forces me to think about 'why' and reading the opinions of others have enlightened me about various aspects. When I'm riding, I pretty much dump all this stuff to the side and enjoy doing what I have found works. When I first starting riding I knew very little about the 'why' it works this way. Through the years I have learned from those far smarter than I, there is more than counter steer to lean and make that turn. We can lean the bike all day and it would never turn without all the other aspects coming together. From leaning, to counter steering, to suspension, to geometry, to rake, trail and off-set, to contact patches and pressure, to weight distribution and side loading, to wind and gyro effect, to gravity and centrifugal force.......and I'm sure I have missed a few! They all work together to fight each other or enhance the relationship, but are balanced in our bikes to provide us with some enjoyable riding.

 

[Slardy]

Early in this discussion an article by David Hough is referenced. The article is titled COMING UNGLUED. Now I happen to think Hough sits right up there beside God when it comes to the mechanics of MC riding. However, he says something in that article that bothers me. Here is a quote from that article:
Try riding the bike in a straight line while standing on the pegs. Get the bike up to 25 mph or so, and then lift your butt off the saddle, placing your weight equally on both footpegs. When that gets familiar, try loading more weight on one peg, and then on the other peg. To keep the bike in a straight line, you'll have to lean it bike away from the peg you're standing on. Remember, you control lean angle by countersteering�to lean the bike left, push on the left grip.

My problem is this sentence: Remember, you control lean angle by countersteering�…

My experience tells me that once I get the bike leaned over via countersteering, any minor steering corrections are not based on countersteering. To move to the left, I steer left and to move right, I steer to the right.

Comments please.

I was just out on the road after a month off due to a minor medical problem. I wanted to test my recollection of how to increase or decrease a turn radius once I have established lean via CS. Well, my recollection as described in Post #62 of this topic, was WRONG. Once I CSed to establish lean, if I wanted to decrease or increase the turn radius, I had to do it via CS. What I did notice was, that because I was only attempting very minor radius corrections, the amount of CS was very, very small. But after riding for over 50 years, CS is so ingrained in my riding style, that I did not even realize that I was doing it for minor radius corrections.

David Hough is returned to his seat next to the God of MC riding technique.

 

[Slardy]

Yeah, I don't agree with his conclusions, but what he is saying is that when the bike is leaned over, the side of the contact patch towards the lean has a smaller circumference around the wheel and the circumference increases across the patch in the direction opposite the lean, which is generally true. And he then extrapolates that this is what causes the bike to turn, like the conical shape cup does when rolled.

Fred, I am going to CS this post into a new direction using a thought of yours. I agree that we may not need to invoke the difference in tire radii when discussing turning at speed in twisties. However, I am quite sure that a difference in contact patch radii, from inside to outside (of a turn), makes a difference in controlling very tight U-turns. I call the technique “coning”. When I attempt a U-turn within the bounds of a 2 lane road, I slow to a crawl, turn the handle bars almost to lock (and to lock sometimes), counter weight the bike by moving my weight to the outside of the turn, keep both feet on the footpegs, and feather my clutch (with constant throttle) to keep the MC under control. With the MC in this configuration, the MC becomes very stable and easy to control. It is almost magical.

Some riders have advised me, when we discuss this situation, that I should press on the outside footpeg. I could care less about footpeg pressure. I don’t think it matters. What does matter is the MC tires are severely tipped into the turn which creates a great degree of tire radii difference between the inside and outside of the tire patch. Now, back to some statements made earlier in this topic, think of rolling a Styrofoam cup or a carrot. For very thigh U-turns, coning does the job.

Check out this Youtube:

Check out the contact patch of the front and real wheels. Looks like coning to me.