The forces placed on a car and its tires during cornering are primarily lateral forces that try to push the car and the tires sideways across the pavement. Conversely, as a motorcycle leans into curves, the cornering force is what is known as camber force. In other words, the force comes at an angle down through the bike and into the tires, instead of across or laterally as with the car. To demonstrate this, grab a pencil with an eraser on one end. Angle the pencil at about 45 degrees, keeping the eraser in contact with the paper. As you press down through the pencil shaft, you are demonstrating camber force, much like the forces common to a cornering motorcycle. The harder you press, the more firmly you plant the eraser into the paper and the pencil resists sliding. Which eraser provides the better contact patch on the paper when the pencil is leaned and pressure is applied: a well-rounded one or a square one?
(This article was published in the July 2012 issue of Rider magazine as a sidebar to Tales From the Dark Side: Car Tires on Motorcycles)