I was hiking in Colorado and talking to another hiker. He pointed out that the pointy tops of the mountains concentrate the gravity there, and that's what makes it so hard to get up them. Maybe that's how the pixie dust works.

I think he's got it! ...and by the way, the gravity thing is also why perpetual motion machines run much longer down in the valleys.

Cool! So then when you steer out of the corner the cornering force is what lifts you back up to vertical.

http://link.brightcove.com/services/...bctid860889923

I'm going with the pixie dust theory.

Actually you steer further into the corner so as to momentarily create greater centrifugal force which brings you back up. It's the most delicate balancing act between forces and the control inputs at the bars and the weight shifting is very subtle and done subconsciously by a competent rider. I find it absolutely amazing how we do it with such ease.

Right! All the way to when cornering forces are zero, and the angle is 90 degrees, i.e. the bike is upright.

Now that part I'm not so sure about. I'm not convinced of the "counter steering" thing either. I know for sure that riding no-handed I can steer my bike by shifting my body weight from side-to-side so I know that I don't have to turn the handlebars to initiate a lean.

Maybe some day somebody will explain it to me in a way that will change my mind.

The same physics that allow you roll a coin on the flat is the same physics that keep a bicycle upright.

Try standing a quarter on it's edge a real smooth surface without it moving... Then roll the same quarter on it's side for quite a distance.

angular momentum helps!

It's so amazing that only humans are capable of such complex and rapid vectoring, lean angle and consciousness of environment decisions to be able to ride a bicycle, especially in busy traffic or on extremely uneven surfaces such as rocky trails.

Of course, this all goes to hell the moment you enter WalMart.

Dont knock wal-mart, not everybody is rich like paris hilton to afford one of those expensive bikes that are worth thousands and can get bike jacked(kick you off it and take it)Thats why john mcsame is not going to become president.If you rode that $4000.00 in my neighborhood and someone knew how much you paid for it,kiss it goodbye.They will kick you off it and it theirs.

Sounds like you should move to a better neighborhood.

Wordbiker and Mark9950. You guys SEEM to be undergoing several misunderstandings. Let me say this thread was going nicely and now I see its stalled. Could it be the conflict turns people off? In my experience yes. Well consider me the exception and let me try and bridge this by calling both of you out.

For one, Wordbiker, I think your response quoted above is lacking. Mark9950 is saying not everybody is rich, and it's not a stretch to say that poor folks don't exactly like living in a neighborhood where bikes get jacked on the street. One perhaps CANNOT move to a nicer neighborhood. For you to suggest that he should is reflecting only ignorance in my mind. Why don't you spend some time learning about the poor so that you do not get eaten by them in some riot or some revolution. all your fancy **** is easy to burn when its 20 angry people. You cannot just get away sometimes so listen and be aware and show some respect. Little quips like yours on the internet just makes for more walls between people.

Mark9950, you don't exactly come away so well either. First, how is he knocking Walmart? I am reading what he wrote, about a human and this uncanny ability to ride a bike in ways more complex than the mind can even understand. And then he says this is no longer the case when you walk into Walmart. He doesn't exactly say WHY this happens in a walmart. Perhaps its because people are shopping and not looking where they are going! happens to rich and poor, they walk around and don't realize that they are demonstrating their own ignorance and arrogance and nothing more. Rick and poor allike, but they do it differently and for different reasons I think.

OWNING a $4000 bike. I will study it, look at the photo, steal its design concepts. Owning, Its not where I want to be really, but I can appreciate spending more and getting a better value. If it is going to cost the same to buy a new walmart bike as have someone repair a broken part on my walmart bike, then maybe The bike is not designed to last. One way around this is to buy a used bike that used to sell for more. In many cases this is a better value, and is not so flashy that someone is going to want to jack it.

I ride in chicago where I've been accosted by thugs on the street. I think tactically and have experience and am not afraid to act. I am prepared in most cases and they never get near me, I see them coming and keep a lot of space between us. This sucks though, young african americans are not always going to be able to check out my bikes because I simply cannot take the risk that something is going to happen. The whole neighborhood becomes a ghetto when nobody wants to go there. the kids have no interesting stuff to look at or people to interact with except those who love them and the thugs and those others somewhere in between.

Still. If somebody jacks a bike in your neighborhood, it isn't exactly, at least for me, going to explain why obama won over mcCain. I have no idea what you mean there.

Anyway, back to physics in the next post!

Consider the bike as an inverted pendulum. If you sit lower to the ground, the natural oscillation frequency of balancing the bike is higher and it's a bit trickier to balance. I found once I got 'bent (sort of like being 'born again', but faster on the downhills) that the sensation of 'leaning' the bike through turns etc is much greater than on an upright bike and the steering inputs to the fork are much less. If you ever get a chance to ride a really low bike like a lowracer recumbent you'll really feel this.

Ok, does Campy make pixie dust? where can I buy it?

To many of you, talking about gyroscopics, or the coin rolling on its edge, I disagree. You are both correct that these forces are there and acting roughly as you describe them, but this is not how the bike stays upright better when moving than when still.

This may be correct, but then I think you can turn the handlebars by applying a sideways or lateral force to the seat and so to the frame. The reasons for this is because the headtube is not directly over the axle and so directly over the tire/ground contact point. Think of a caster wheel, you push and it swings around. If the caster wheel's swivel mount point, its axle, and thus where it contacts the ground were all aligned, no trail, you would skid the wheel and it would tend not to swing around, this is what your track bike is like.

I'm off to review my understanding at that wikipedia link.

Per Bicycle Science published by MIT Press gyroscopic action of the wheels has minimal/no effect as bikes have been built with additional counterrotating weights to cancel gyroscopic wheel forces and they are as easy to ride as a normal bike.

I know the answer, but I'm not tellin'. Sorry.

Its vexing.

I think there is pixie dust in there too. Like how an animal that walks on two legs, but not more, has the necessary aptitude, maybe.

how about counter steering. wikipedia says that every turn starts by turning the other direction. If I read it correctly.

Aerodynamics, and then the rider's ability to shift weight. Frame flex, cross winds, reaction times. I would not be surprised to hear we don't understand it yet, because something "new" came up.

I say, why act all confident about it?

edit: having ridden inebriated before, perhaps reaction times are not so critical

Clearly, bikes have not evolved through Intelligent Design, otherwise they would be able to stay upright on their own, without human intervention.

So Darwin was right after all.

Alternatively, Pixie dust tends to be affected by static electricity and clumps together unevenly in the tyre tread, thereby producing an unbalanced wheel, which is why only people blessed with the ability to telekinetically distribute the PD evenly round the tyres can trackstand properly.

Unfortunately, this ability is not under conscious control, so it cannot be learned. If you claim that constant practice has enabled you to do this, I am afraid you do so in error. What happened is that concentrating on trying to trackstand has allowed your subconscious free reign until your latent telekinetic ability is freed from the constraints of rational thinking.

for the same reason that tires go flat faster when you don't ride: when your bike is not ridden, it quickly gets depressed. it becomes sad, deflated, and tired, and just wants to lie down.

on the other hand if you ride it, even for a millimeter, it quickly becomes happy.

This has been the best thread. I was sad to see it peter out. The pixie dust theme got a bit tired, but then someone mentions 'WalMart' and then boom!
Good times.
Tomorrow I think I'll start a thread asking, "Why are bikes skinnier than cars, yet wider than pieces of plywood?"
Hopefully someone will mention polar bears.

Lets get back to the physics of mountain peaks!

So, if "the pointy tops of the mountains concentrate the gravity there" (called a gravity well), then it should be easier to get to the top of the peak with the greater gravity pulling you up.

Now someone explain to me how gravity can possibly pull two objects with mass together, or is it really space pushing the two objects with mass together?

http://www.hbci.com/~wenonah/new/gravity.htm

I take it, that you have not looked at any of the new Time Trial bikes lately! side view = :speedy: front view = T

In the case of trackstanding, which was the original example for this thread, the reason is simple. When you trackstand, you generally turn the handlebars to one side. As you move forward, the bike moves to that side, and when you move backward the bike moves to the other side. With practice, you can use the lateral movement to keep the bike under your center of gravity.

The answer to the original question, or example if you want is

Bikes are not usually designed for balancing while not rolling.