# How come you have more stability riding a bike than standing still with a bike?

• Femme_physics
In summary, a well-made bicycle has a natural tendency to turn in the direction it is leaning. This makes bicycle riding feel intuitive and natural. When you are standing still and feel like you are about to fall over, you steer to the opposite direction to prevent yourself from falling. If you are moving and feel like you are about to fall over to the left, you steer to the left to move the contact patches of the wheels under you back to the center. As you lean the bike to the right, you follow that with the handlebars.
Femme_physics
Gold Member
My friend asked me that this morning but I couldn't think of the answer. I know there's probably some major physical law behind it, but so many to choose from! Can you guys help me clarify this issue for myself and my friend?(when I say "riding a bike" - I mean riding on a bike. When I say "standing still with a bike", I mean sitting still on a bike)...

Two effects. Main one is the fact that the fork is angled, so the front wheel turns in the direction you lean in. That makes you go along a curve, and that causes centrifugal force to push you straight again.

Second one is gyroscopic effect on the wheel. This one is significantly stronger on a motorcycle, but it contributes to the bicycle's stability as well.

Keep in mind that in order to lean, you usually use a counter-turn first. Especially on a motorcycle. That's not always explained very well.

To be in balance the center of gravity of you and the bicycle combined must be straight above the contact patches of the wheels.

If you are standing still, and you start to fall over, then you are forced to put your foot on the ground.

When you are moving, and you feel you are in danger of falling over to the left, you steer ever so slightly to the left, thus moving the contact patches of the wheels underneath you again. (In actual bicycle riding the contact patches are only on average right underneath the center of gravity.)

As K^2 pointed out, in order to corner to the right you initiate the cornering by turning the handle bars slightly to the left - just for a fraction of a second. That moves the contact patches away from right underneath you. As the bicycle start to lean you follow that with the handlebars.

A well manufactured bicycle has a natural tendency to turn in the direction in which it is leaning. That is what makes bicycle riding feel natural and intuitive

By the way:
I think this countersteering is a striking example of subconscious learning. To corner means you have to countersteer. (Well, in the case of a very wide corner the countersteering is so subtle that it drowns in the random wriggling of cycling.)
Most people are unaware they are using countersteering. The skill has been acquired through trial and error, with no conscious perception of what is going on.

Try a bike with opposite steering, i.e. one of those clown bikes. They are difficult I can tell you!

Even worse when you have to pedal backwards to get forward...

[PLAIN]http://www.weiwong.com/image.axd?picture=2009/01/reverse-bike-1.jpg

Last edited by a moderator:
Cleonis said:
To be in balance the center of gravity of you and the bicycle combined must be straight above the contact patches of the wheels.

If you are standing still, and you start to fall over, then you are forced to put your foot on the ground.

When you are moving, and you feel you are in danger of falling over to the left, you steer ever so slightly to the left, thus moving the contact patches of the wheels underneath you again. (In actual bicycle riding the contact patches are only on average right underneath the center of gravity.)

As K^2 pointed out, in order to corner to the right you initiate the cornering by turning the handle bars slightly to the left - just for a fraction of a second. That moves the contact patches away from right underneath you. As the bicycle start to lean you follow that with the handlebars.

A well manufactured bicycle has a natural tendency to turn in the direction in which it is leaning. That is what makes bicycle riding feel natural and intuitive

By the way:
I think this countersteering is a striking example of subconscious learning. To corner means you have to countersteer. (Well, in the case of a very wide corner the countersteering is so subtle that it drowns in the random wriggling of cycling.)
Most people are unaware they are using countersteering. The skill has been acquired through trial and error, with no conscious perception of what is going on.

So, how come when I'm standing and I feel the danger of falling down, I can't just steer to the opposite direction and stay still? It still doesn't explain how motion is different. I supposed though from what I understand that momentum reduces weight...

That's because when you steer, even when you are standing in place, it results in shifting the frame, and therefore, the position of CoM relative to contact patches. This effect is fairly small, however, so you have to be almost perfectly balanced, and only make small corrections. If you actually start to fall over, you cannot stop it without moving forward or using your foot.

Try a bike with opposite steering, i.e. one of those clown bikes. They are difficult I can tell you!
Don't need a clown bike for that. Just grab handle bars on ordinary bike cross-hand and try not to hurt yourself when you fall.

## 1. Why is it easier to balance on a bike while in motion?

When a bike is in motion, the wheels create a gyroscopic effect that helps stabilize the bike. This effect is created by the rotating motion of the wheels, which creates a force that resists any changes to the bike's orientation. This makes it easier for the rider to maintain their balance while riding.

## 2. How does the center of mass affect bike stability?

The center of mass is the point where the mass of an object is concentrated. In the case of a bike, the rider's center of mass is located above the wheels. When the bike is moving, the rider's center of mass is constantly shifting and adjusting to maintain balance, making it easier for the rider to stay upright.

## 3. What role do the brakes play in bike stability?

The brakes on a bike can actually help with stability. When a rider applies the brakes, the front wheel of the bike is pulled closer to the ground, making the bike more stable. This is because the front wheel acts as a pivot point, allowing the bike to rotate around it and remain upright.

## 4. How does momentum contribute to bike stability?

When a bike is in motion, it has momentum, which is the tendency of an object to continue moving in the same direction. This momentum helps keep the bike stable by resisting any sudden changes in direction or speed. This is why it is easier to maintain balance while riding a bike rather than standing still with a bike.

## 5. Is there a difference in stability between a bike with two wheels and a bike with three wheels?

Yes, there is a difference in stability between a two-wheeled bike and a three-wheeled bike. Two-wheeled bikes rely on the rider's balance and momentum to stay upright, while three-wheeled bikes have a wider base and are more stable. This is why three-wheeled bikes, such as tricycles, are often used by children who are still learning how to balance on a bike.

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