[buvanshak]

>If you lean left, front wheel will "do" countersteering itself (same as noted).

I am not sure. If you lean left, then the handle bar ll slightly turn left automatically.

In actual countersteering, it greatly helps only because it helps to quickly initiate a tilt in the required direction. For example, if you want to go to left, then turn the handle bar to the right, which causes the front wheel to slight start to offset in the right, which in turn causes the whole bike to tilt to left, and once it start to tilt to the left, then the normal process of turning is applied...

[ska]

It's always countersteering. Doesn't even matter if your hands are on the bars (really).

When you lean to (your) left, the center of mass of you+bike goes left of the plane of the wheels, this causes the front wheel to rotate away (i.e. right) from the motion slightly which causes you to bank left and the front wheel comes around to meet it until you are in equilibrium again.

Countersteering doesn't "help", it's just unavoidable. Being aware of it helps you have better control. At very low velocities the effect is so minor you probably can't notice (and steering angles are large).

[buvanshak]

> When you lean to (your) left, the center of mass of you+bike goes left of the plane of the wheels, this causes the front wheel to rotate away

This does not seem correct. Why does it cause the front wheel to rotate away (right) ?

If you lean a stationary cycle to the left, the front wheel will turn left.

[ska]

  Why does it cause the front wheel to rotate away (right) ?

Answer is : "it's complicated" , which is why this subject causes confusion. There are many arguments about the exact dynamics (combinations of gyroscopic effects, torques, center-of-mass motion), but empirically it is pretty clear that two wheeled vehicles like bikes/motorcycles do not turn without counter-steer.

[jonsen]

Not at all complicated. A bike is made so that the front wheel will turn in the same direction as the bike is leaned. This has a simple stabilising effect. Bike leans right, front wheel turns right, increased centrifugal force from the sharper turn will unlean the bike to the left.

[buvanshak]

> Bike leans right, front wheel turns right

Agree. But this is not what the other person is saying.

[ska]

Except, it doesn’t at first. Which is why this is counter intuitive.

[jonsen]

If you lean your body to the left the bike reacts by leaning to the right. Your body can only move by pushing the bike in the opposite direction.

[NLips]

I shouldn't have mentioned 'leaning left'.

If I'm in contact with the top of my bike and not steering the bars, I can either push the top of the bike left or right. I push the top of the bike to the left. The bike and I have separate moments of intertia around longitudinal axis. Without any other forces involved (just my bum and the top of the bike pushing each other), the bottom of the bike i.e. the contact patch would move to the right. However, there's friction between the tyres and the ground meaning that doesn't happen. Instead, the ground pushes the bottom of the wheels to the left. This means the only external force on the union of rider and bike is from the ground pointing leftwards. This pushes the COG to the left.

While the motion of the top of the bike may cause some countersteering in the front wheel if left free, you can resist this by pushing the right side of the handlebars i.e. steering left. So we now have a bike tilting to the left, with the front wheel pointing forwards, and the COG to the left of the contact patches. The front wheel can be gently pushed to point left.

No countersteering involved.

[buvanshak]

That is bullshit. If I just lean to the left, the bike does not "react" by leaning to the right. If I lean to the left without touching the handle bars, the cycle ll start turning to the left.

With counter steering, it can be made much quicker and in a much responsive fashion.

[ska]

The point is that the wheel, which is free, will turn to the right first. The bike will lean to the left as this takes the two wheels out of line. The wheel will follow to the left.

There is nothing magical about countersteering, it’s just the way cornering works with bikes.

Don’t believe me? Set up an angle indicator and video it.

[buvanshak]

A bike is standing straight, completely still, with the front wheels completely straight. According to you, if I lean this stationary bike, to left, you are saying the front wheel will turn to right, right?

[Declanomous]

The part you are missing is the gyroscopic procession from the wheels. When you try turning the wheel to the left, you create a force that is 90 degrees to force.

If you just turn the handlebars (which would cause the bike to lean in the direction of the turn), you will end up creating a force at the top of the wheel in the opposite direction of your tilt. (e.g. the force will be at 12 o'clock)

If you just lean in the direction you'd like to turn, the wheel will turn in the opposite direction of the lean. (e.g. there will be an opposite force at 9 o'clock)

In order to turn you must always briefly steer in the opposite direction you'd like to turn, so that you may lean in the direction you'd like to turn, which will allow you to turn the wheel in the direction of the turn without upsetting the bike.

I learned this fact about 2 years ago and I've been hyper-aware of the fact ever since. Try as I might, it's literally impossible to steer a bike without counter-steering.

The fact that you absolutely must counter-steer to turn is one of the reason why inexperienced bike riders tend to fall over when they need to steer in an emergency, because they just twist the handlebars, which catapults them off the other side.

Knowing this also helped me finally learn to ride a bike with no handlebars, since you have to lean opposite the direction you'd like the wheel to go.