How Do Motorcycles Turn?

Teaching motorcycle safety classes, I’ve come across many people who think they understand how a motorcycle turns and are completely wrong.

Some people think that it’s about throwing or shifting one’s body weight into the corner to lean the motorcycle over. In fact, pressing forward on the handgrip in the direction you are turning — in other words, pressing in a way that causes your tire to begin to turn away from direction you want to go — triggers a complex mess o’ physics that’s way over my head because I copied Joe Smith’s answers in my high school Physics class.

The act of turning the tire away from the turn is known as countersteering. I suspect those people who argue that they lean with their body end up putting pressure on the inside handgrip and countersteering without realizing that it happens.

That was certainly the case with me. I’ve ridden from a very young age and was a reasonably competent rider. I didn’t have any problem leaning into a turn and holding my line. But I had a number of close calls where, at very low speeds, I needed to avoid clipping a vehicle or some other object and found myself squirming and moving my butt to the side. I’d squeak past, but just barely. And I couldn’t understand why I didn’t have better directional control in those situations.

It was only after I’d become an instructor — my first exposure to formal riding education — that I understood that in those panicked moments I was trying to turn my front tire away from the obstacle and that countersteering was sending me closer to it. What came naturally in a long, sweeping curve went out the window when I was thinking desperately about it.

This YouTube video does a fantastic job of showing how countersteering works and explains it in a way that even Mr. Cantwell’s worst “C” student can understand.

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2 Responses to How Do Motorcycles Turn?

  1. Bill Chapman says:

    A motorcycle leans over when you counter steer but that is not the reason it turns. The reason it turns is that the sides of the tire have a smaller radius than the center. in effect a motorcyle tire is like two truncated cones joined at the fat end. As soon as the tire gets off the middle you have an unequal radius oject rolling, i.e. a rolling cone. Since the fat end of the cone and the skinny end have to turn at the same number of revolutions, but the fat end has to cover much more ground, the whole thing must turn. The physics is very simple and you can demonstrate it yourself with any rubber donut. I am amazed at the confusion over how motorcycles turn.

  2. curt says:

    I was wondering the same thing bill. Counter steering is the fastest way to get your motorcycle to turn. But as bill says its not what makes the motorcycle actually turn.

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