Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes referred to as "giving a steering command". The scientific literature does not provide a clear and comprehensive definition of countersteering. In fact, "a proper distinction between steer torque and steer angle ... is not always made." How it works When countersteering to turn right, the following is performed: A torque on the handlebars to the left is applied. The front wheel will then rotate about the steering axis to the left and the tire will generate forces in the contact patch to the left. The machine as a whole steers to the left. Because the forces in the contact patch are at ground level, this pulls the wheels "out from under" the bike to the left and causes it to lean to the right. The rider, or in most cases the inherent stability of the bike, provides the steering torque necessary to rotate the front wheel back to the right and in the direction of the desired turn. The bike begins a turn to the right. While this appears to be a complex sequence of motions, it is performed by every child who rides a bicycle. The entire sequence goes largely unnoticed by most riders, which is why some assert that they do not do it. It is also important to distinguish the steering torque necessary to initiate the lean required for a given turn from the sustained steering torque and steering angle necessary to maintain a constant radius and lean angle until it is time to exit the turn. The initial steer torque and angle are both opposite the desired turn direction. The sustained steer angle is in the same direction as the turn. The sustained steer torque required to maintain that steer angle is either with or opposite the turn direction depending on forward speed, bike geometry, and combined bike and rider mass distribution. Need to lean to turn A bike can negotiate a curve only when the combined center of