Countersteering is the technique used by cyclists and motorcyclists to initiate turning toward a given direction by first steering counter to the desired direction ("steer left to turn right"). In order 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 momentarily in the opposite direction causes that lean. Once sufficient lean is established to sustain the desired turn, the rider, or in many cases the bike itself, then steers into the turn to cause the bike to turn in the desired direction and stop the lean from increasing.
It is important to distinguish between countersteering as a physical phenomenon and countersteering as a rider technique for initiating a lean (the usual interpretation of the term). The physical phenomenon always occurs, because there is no other way to cause the bike and rider to lean short of some outside influence such as an opportune side wind, although at low speeds it can be lost or hidden in the minute corrections made to maintain balance.
At the same time, the rider technique of applying pressure to the handlebars to initiate a lean is not always necessary, since, on a sufficiently light bike (especially a bicycle), the rider can initiate a lean and turn by shifting body weight. Documented physical experimentation shows that on heavy bikes (many motorcycles) shifting body weight is ineffective at initiating leans.
It is also important to distinguish the momentary steering torque and steering angle 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, momentary 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.
Hence, if a rider wants to turn to the right, he first throws the bike off balance by momentarily pointing the front wheel slightly to the left. The center of mass of the bike plus rider will continue in a straight line, but the contact patches of the tires move to the left with respect to this straight line.
The actual torque the rider must apply to the handlebars in order to maintain a steady-state turn is a complex function of bike geometry, mass distribution, rider position, turn radius, and forward speed. At low speeds, the steering torque necessary from the rider is usually negative, that is opposite the direction of the turn, even when the steering angle is in the direction of the turn. At higher speeds, the direction of the necessary input torque inverts to become positive, that is in the same direction as the turn.
To exit a turn, countersteer by momentarily steering further in the direction of the turn. This tilts the bike back upright.
As is well-known in bicycle racing, the countersteering phenomenon becomes evident when there is an obstacle preventing the wheel from countersteering (e.g., when closely overlapping wheels or riding very close to a curb). In these situations, the only way to initiate a turn away from the obstacle is to come into contact with it, that is, turn towards the wheel or curb in order to avoid crashing into it. Lack of understanding of this principle leads to accidents in novice bicycle races.
For a sample motorcycle moving at 22 m/s (50 mph) that has a front wheel with a moment of inertia of 0.6 kgm2, turning the front wheel one degree in half a second generates a roll moment of 3.5 Nm. In comparison, the lateral force on the front tire as it tracks out from under the motorcycle reaches a maximum of 50 N. This, acting on the 0.6 m (2 ft) height of the center of mass, generates a roll moment of 30 Nm.
While the moment from gyroscopic forces is only 12% of this, it can play a significant part because it begins to act as soon as the rider applies the torque, instead of building up more slowly as the wheel out-tracks. This can be especially helpful in motorcycle racing.
To straighten back out of the turn, the rider simply reverses the procedure for entering it: cause the bike to lean farther to the left; this causes it to steer farther to the left which moves the wheel contact patches farther to the left, eventually reducing the leftward lean and exiting the turn.
The reason this no-hands steering is less effective on heavy bikes, such as motorcycles is that the rider weighs so much less than the bike that leaning the torso with respect to the bike does not cause the bike to lean far enough to generate anything but the shallowest turns. Riders may be able to keep a bike centered in a lane and negotiate shallow highway turns, but not much else.
Much of the art of motorcycle cornering is learning how to effectively "push" the grips into corners and how to maintain proper lean angles through the turn. When the need for a quick swerve to one side suddenly arises in an emergency, it is essential to know, through prior practice, that the handlebars must be deliberately pressed away on that side instead of being pulled. Many accidents result when otherwise experienced riders who have never carefully developed this skill encounter an unexpected obstacle.
US Patent Issued to Bayerische Motoren Werke on March 29 for "Countersteering Rear Vehicle Axle" (German Inventor)
Apr 05, 2011; ALEXANDRIA, Va., April 5 -- United States Patent no. 7,914,019, issued on March 29, was assigned to Bayerische Motoren Werke AG...
US Patent Issued to Bayerische Motoren Werke on July 17 for "Countersteering Rear Axle of a Vehicle" (German Inventor)
Jul 18, 2012; ALEXANDRIA, Va., July 18 -- United States Patent no. 8,220,810, issued on July 17, was assigned to Bayerische Motoren Werke AG...