The steering geometry is exactly the same.

The only time you steer left to go left is if you're going so slowly that the only reason the bike doesn't fall over is because of your near-superhuman balance. That is to say, when you're practically at a standstill. Anywhere approaching walking pace or above, if you try to turn left by steering left, you'll fall off the right hand side before you make any appreciable turn.

> if you try to turn left by steering left

Well, if you're leaning left when steering left, I don't see how you'll fall to the right

That's the issue; how do you lean left to start with? If the human-bicycle system has its center of gravity over the wheel line, shifting your weight relative to the bike doesn't move the center of gravity - you lean one way, the bike leans the other, and you end up in the same overall position. The only way to initiate a lean to the left is to countersteer to the right.

That's weird since I don't think I'm countersteering when turning.

Or perhaps I'm doing it unconsciously?

> Or perhaps I'm doing it unconsciously?

You are. I proved this to myself once by applying pressure to the handlebars using only the palm of my hands on the backside of each handle. Even at very slow speeds, I could not for the life of me turn left by applying pressure only to the right bar (to turn the front wheel to the left). No amount of leaning helped. To lean the bike, I needed to create some external force to push it over. Leaning my own body to the left just made the bike lean to the right.

I'll have to check, because I don't believe it. I wonder who's right: me or a bunch of randos on an internet thread.

I've seen the same claim from a lot of people who seemed to have thought about it a lot: that you always countersteer on a two-wheeled vehicle, but you only do so consciously if you're riding a very fast vehicle or you want to turn extremely quickly. (A deliberate countersteer is taught in some bicycle safety classes as an "emergency quick turn".)

This is counterintuitive to me as a regular cyclist, but I realize that most of my cycling skills are completely unconscious, so I don't have a lot of confidence in my ability to describe exactly what I'm doing on my bike.

I've only ever riden a bike and very rarely at high speed (for a bike), so that explain why I never had to countersteer consciously.

That's what I used to think until I started taking motorbike lessons.

At first I was having a hard time turning, because this whole counter-steering thing didn't come naturally to me and I would try to turn the handlebars to the left if I wanted to go left, but the bike would go the other way witch was pretty scary.

I then internalised this and the next time I rode a bike I tried this out, and indeed, this is how it works. If I turned the handlebars left at any considerable speed, the bike would lean to the right and start turning right, with the handlebars going right. It would go a slight bit left at the very beginning, but then it would go all the way right.

When I think about it, at slow speeds (say below 25 km/h - 15 mph) I only turn the handlebars and lean the bike. However, I can lean the bike at those speeds, so no counter-steering is required. I first lean the bike and then turn the bars. However, it's very difficult to have it lean any useful amount at speed. And this is where counter-steering is useful.

Here's a video where this is all explained, complete with fixed handlebars (that don't steer the wheel) to show how just leaning doesn't do much : https://www.youtube.com/watch?v=8_5Z3jyO2pA&feature=youtu.be...

Granted, this is way more noticeable on a motorbike that on a bicycle. Maybe the weight of the wheels and of the whole bike has something to do with it. If I lean a 10 kg bike but stay upright on it, the centre of gravity doesn't move much. However, on a 300 kg motorcycle, it moves quite a bit more.

> If you lean left, front wheel will "do" countersteering itself

The same applies to a bicycle.

> Only on a motorbike.

Only above a certain speed, at low speeds countersteering will not work

Similarly above a certain speed on a bicycle countersteering is the only way you can turn

Some people seem to describe this difference as unconscious countersteering versus deliberate countersteering, that is, that the difference isn't really whether you're countersteering or not, but whether the countersteer is large enough that you have to do it "on purpose".