Читать книгу Proficient Motorcycling - David L. Hough - Страница 56

While your bike is leaned over in a curve, you might wonder why the bike continues to turn even though the front end seems to be pointed straight ahead. Part of the reason is that the front wheel really is pointed slightly toward the curve. The other part of the reason is called coning. To understand the concept of coning, let’s consider the shape of the front tire where it meets the road surface.

The motorcycle pictured above is in a straight line, approaching the turn-in point.

As the rider countersteers, the front wheel actually tracks away from the intended direction of turn.

With the motorcycle leaned, the front wheel recenters and then steers toward the turn.

When the wheel is leaned into a turn, the flexible tire forms a contact ring that is conical in shape, similar to the shape of a foam coffee cup on its side.

Although we can see that the top of an inflated tire forms a rounded shape, we have to imagine that the tire momentarily gets flattened where it contacts the ground at the CP. And we also know that the tire CP isn’t really a single point but rather a continuous ring around the tread. It’s important to recognize that with the bike leaned over into a turn, this contact ring forms a conical shape, similar to a foam coffee cup on its side.

If you nudge the cup forward, it wants to roll in a circle because the circumference at the closed end is smaller than the circumference at the open end. If you stick a toothpick through the center of the cup bottom, the toothpick will point approximately at the center of the circle. A motorcycle tire responds similarly when the bike is leaned over, with the inside of the tire contact surface covering less distance than the outside. So when leaned, a motorcycle wheel wants to roll in a circle, with the axle pointed more or less at the center of the turn. In a very tight turn, the axle may actually point at a center that’s below the surface of the ground.