# Physics of riding a motorcycle

1. Jun 15, 2009

### thomasxc

my father recently took a motorcycle class he had to take in order to be able to legally ride one. he said we was told that, in order to turn at high speed, he was supposed to push on the side of the handlebar that he wanted to go. as in, he had to push with his left hand and pull with his right in order to turn left. if this is correct, i dont understand the physics in it. does anyone else know?? thanks.

2. Jun 15, 2009

### Staff: Mentor

It's called "countersteering", and is one way of steering a motorcycle. We've had discussions about countersteering and "bodysteering" (a different way to steer) here on the PF before... I'll see if I can find them with a search...

3. Jun 15, 2009

### Staff: Mentor

4. Jun 15, 2009

### rcgldr

Short version: In order to turn left, you have to lean left; to lean left, you have to steer right briefly (so that tires are steered right from under you, leaning the bike left); once leaned, you steer left, ... and vice versa.

The steering geometry of most motorcycles is designed to steer excessively inwards based on the lean angle (and reasonable speeds), which cause the motorcyle to return or remain vertical without steering inputs. Once leaned, the excessive inwards steering requires a bit of outwards steering torque applied to the handlebars is needed to hold a lean angle on most motorcycles. Braking while leaned can increase the excessive inwards steering response. Some racer-replica sport bikes are designed to minimize the excessive inwards response, but are a bit less stable.

5. Jun 15, 2009

### gmax137

Well I hope they did more than "tell" him this. As in, I hope the class included an opportunity to do it. No argument or physics-based explanation can substitute for the almost magically 'quick' change in direction induced by actually pushing on the bars at speed. Countersteering flat works. And the more you do it, the more natural it seems.

6. Jun 16, 2009

### thomasxc

he did say it worked. and i think its interesting simply because it seems counter-intuitive. then again, so are a lot of physics phenomena.

7. Jun 16, 2009

### Ranger Mike

exact opposite of driving a snow mobile

8. Jun 16, 2009

### Integral

Staff Emeritus
This works on bicycles as well. Hi speed is not necessary. Just apply a gentle pressure and get ready to lean and turn.

9. Jun 16, 2009

### thomasxc

the second thread is a good one, berkeman.thx.

10. Jun 16, 2009

### thomasxc

and i am on my way outside to try that, integral. hah.

11. Jun 16, 2009

### thomasxc

i jumped on the bicycle. it totally works, and that's totally awesome! (forgive my 17 year-old, lacking vocabulary.)

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