Countersteering is the technique used by single-track

Single-track vehicle

A single-track vehicle is a vehicle that leaves a single ground track as it moves forward. Single-track vehicles usually have little or no lateral stability when stationary but develop it when moving forward or controlled...

 vehicle

Vehicle

A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

 operators, such as cyclists

Cycling

Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...

 and motorcyclists

Motorcycling

Motorcycling is the act of riding a motorcycle. A variety of subcultures and lifestyles have been built up around motorcycling.-Benefits:Robert M. Pirsig's book Zen and the Art of Motorcycle Maintenance was a paean celebrating motorcycling...

, 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

Center of mass

In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

 of the rider and the single-track vehicle

Vehicle

A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

 must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. This technique does not apply to conventional multiple-tracked vehicles such as trikes or sidecar

Sidecar

A sidecar is a one-wheeled device attached to the side of a motorcycle, scooter, or bicycle, producing a three-wheeled vehicle.-History:A sidecar appeared in a cartoon by George Moore in the January 7, 1903, issue of the British newspaper Motor Cycling. Three weeks later, a provisional patent was...

 equipped bicycles and motorcycles.

It is important to distinguish between countersteering as a physical phenomenon and countersteering as a conscious 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 handlebar

Handlebar

A handlebar is part of the steering mechanism, in lieu of a steering wheel, for vehicles that are ridden on, instead of in, such as bicycles, motorcycles, tricycles, ATVs, snowmobiles and personal watercraft. It may also be simply the handles on a device such as a zip line trolley or a floor buffer...

s to initiate a lean is not always necessary, since, on a sufficiently light bike (especially a bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

), the rider can initiate a lean and turn by shifting body weight, called counter-lean by some authors.
Documented physical experimentation shows that on heavy bikes (many motorcycle

Motorcycle

A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...

s) shifting body weight is less effective at initiating leans.

It is also important to distinguish the steering torque and steering angle necessary to establish the lean required for a given turn from the sustained steer torque and steer angle necessary to maintain a constant radius and lean angle until it is time to exit the turn. The initial steer torque and steer angle are both opposite the desired turn direction. The sustained steer angle is usually in the same direction as the turn, but may remain opposite to the direction of the turn, especially at high speeds. The sustained steer torque required to maintain that steer angle is usually opposite the turn direction. (See the graphs to the right.) The actual magnitude and orientation of both the sustained steer angle and sustained steer torque of a particular bike in a particular turn depend on forward speed, bike geometry, tire properties, and combined bike and rider mass distribution.

Bikes vs automobiles

Automobiles steer by imposing a steer angle between the front and rear wheels. Broadly speaking, the response of the vehicle is related to that angle; the automobile is a "position-controlled" system in normal use.

Bikes steer by controlling roll angle. However roll angle is not directly manipulated by the handlebars in the same way as steer angle in an automobile. Rather it is influenced indirectly by applying roll moments to the machine. These roll moments in turn come from side forces at the wheels, which are closely related to steering torques. Thus the bike is a "force-controlled" system in which the actual position of the handlebars is free.

The lean of a bike's wheels causes a turning force in the direction of the lean, called camber thrust

Camber thrust

Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its camber angle and finite contact patch...

, which enables the bike to negotiate turns with substantially less steering angle of the front wheel than an automobile for the same turn radius.

How it works

A single-track vehicle such as a bicycle or a motorcycle is an inverted pendulum

Inverted pendulum

An inverted pendulum is a pendulum which has its mass above its pivot point. It is often implemented with the pivot point mounted on a cart that can move horizontally and may be called a cart and pole...

—it will fall over unless balanced.

The technique used by cyclists

Cycling

Cycling, also called bicycling or biking, is the use of bicycles for transport, recreation, or for sport. Persons engaged in cycling are cyclists or bicyclists...

 and motorcyclists

Motorcycling

Motorcycling is the act of riding a motorcycle. A variety of subcultures and lifestyles have been built up around motorcycling.-Benefits:Robert M. Pirsig's book Zen and the Art of Motorcycle Maintenance was a paean celebrating motorcycling...

 to initiate turning in a given direction is to first apply a steering torque in the opposite direction. For example, if a turn to the left is desired, it is started by a turn of the handlebars to the right. Under this force the front wheel will rotate to turn right and the front tire will generate forces to the right. The machine as a whole steers to the right briefly and the rear tire also generates forces to the right. Because the forces are applied at ground level, this pulls the wheels "out from under" the motorcycle and to its right. The resulting roll angle to the left causes the tires to then generate camber thrust

Camber thrust

Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its camber angle and finite contact patch...

 to the left providing the centripetal forces required to turn left. The geometry of the steering system provides the forces necessary for the front wheel to adopt an angle turned into the turn in a conventional manner. It is often boiled down to "push left to go left".

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 often claimed that two-wheeled vehicles can be steered using only weight shifts. While this is true for small "trim" inputs to direction, complex maneuvers are not possible using weightshifting alone because even for a light machine there is insufficient control authority.
Although on a sufficiently light bike (especially a bicycle

Bicycle

A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....

), the rider can initiate a lean and turn by shifting body weight, there is no evidence that complex maneuvers can be performed by bodyweight alone.

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.

Countersteering is necessary to adjust the angle of lean of a bicycle and works in the opposite sense to the handlebar input while conventional steering in the direction of the turn is used in conjunction with camber thrust

Camber thrust

Camber thrust and camber force are terms used to describe the force generated perpendicular to the direction of travel of a rolling tire due to its camber angle and finite contact patch...

 to negotiate the turn.

Need to lean to turn

A bike can negotiate a curve only when the combined center of mass

Center of mass

In physics, the center of mass or barycenter of a system is the average location of all of its mass. In the case of a rigid body, the position of the center of mass is fixed in relation to the body...

 of bike and rider leans toward the inside of the turn at an angle appropriate for the velocity and the radius of the turn:

where is the forward speed, is the radius of the turn and is the acceleration of gravity.

Higher speeds and tighter turns require greater lean angles. If the mass is not first leaned into the turn, the inertia

Inertia

Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...

 of the rider and bike will cause them to continue in a straight line as the tires track out from under them along the curve. The transition of riding in a straight line to negotiating a turn is a process of leaning the bike into the turn, and the only way to cause that lean (of the combined center of mass of bike and rider) is to move the support points in the opposite direction first. The rider can shift his weight of course, but any force used to move one way laterally pushes the bike laterally the opposite direction with equal force. That makes the bike lean (and can affect the steering), but it does not change the combined center of mass of bike and rider.

Lean by countersteering

When riding a bicycle or a motorcycle, countersteering is a method of initiating a turn by a small, momentary turn of the front wheel, usually via the handlebars, in the opposite (counter) direction. This moves the pivot point (the wheels' contact patches) out from under the center of mass to establish the lean angle for a turn. While necessary at all speeds, the need to countersteer becomes more noticeable as speed increases.

Hence, to turn to the right, the rider 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 patch

Contact patch

Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...

es of the tires move to the left with respect to this straight line.

Once lean is achieved

As the desired angle is approached, the front wheel must usually be steered into the turn to maintain that angle or the bike will continue to lean with gravity, increasing in rate, until the side contacts the ground. This process often requires little or no physical effort, because the geometry of the steering system of most bikes

Bicycle and motorcycle geometry

Bicycle and motorcycle geometry is the collection of key measurements that define a particular bike configuration. Primary among these are wheelbase, steering axis angle, fork offset, and trail...

 is designed in such a way that the front wheel has a strong tendency to steer in the direction of a lean.

The actual torque the rider must apply to the handlebars to maintain a steady-state turn is a complex function of bike geometry, mass distribution, rider position, tire properties, 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 often becomes positive, that is in the same direction as the turn.

Adjusting or exiting a turn

Once in a turn, countersteering is again required to make changes to its shape. The only way to decrease the radius at the same speed is to increase the lean angle, and the only way to increase the lean angle, is again to momentarily steer opposite to the direction of the curve. To the untrained, this can be extremely counter-intuitive.

To exit a turn, countersteer by momentarily steering further in the direction of the turn. This tilts the bike back upright.

At low speeds

At low speeds countersteering is equally necessary, but the countersteering is then so subtle that it is hidden by the continuous corrections that are made in balancing the bike, often falling below a just noticeable difference

Just noticeable difference

In psychophysics, a just noticeable difference, customarily abbreviated with lowercase letters as jnd, is the smallest detectable difference between a starting and secondary level of a particular sensory stimulus...

 or threshold of perception of the rider. Countersteering at low speed may be further concealed by the ensuing much larger steering angle possible in the direction of the turn.

Unthinking behavior

Countersteering is indispensable for bike steering. Most people are not aware that they employ countersteering when riding their bike any more than they are aware of the physics of walking. They have learned to apply the required countersteering without thinking.

As is well-known in bicycle racing

Bicycle racing

Bicycle racing is a competition sport in which various types of bicycles are used. There are several categories of bicycle racing including road bicycle racing, cyclo-cross, mountain bike racing, track cycling, BMX, bike trials, and cycle speedway. Bicycle racing is recognised as an Olympic sport...

, 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, countersteer towards the wheel or curb to avoid crashing into it. Lack of understanding of this principle leads to accidents in novice bicycle races.

Gyroscopic effects

One effect of turning the front wheel is a roll moment

Moment (physics)

In physics, the term moment can refer to many different concepts:*Moment of force is the tendency of a force to twist or rotate an object; see the article torque for details. This is an important, basic concept in engineering and physics. A moment is valued mathematically as the product of the...

 caused by gyroscopic precession

Precession

Precession is a change in the orientation of the rotation axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle is constant...

. The magnitude of this moment is proportional to the moment of inertia

Moment of inertia

In classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...

 of the front wheel, its spin rate (forward motion), the rate that the rider turns the front wheel by applying a torque to the handlebars, and the cosine of the angle between the steering axis and the vertical.

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

Motorcycle racing

Motorcycle sport is a broad field that encompasses all sporting aspects of motorcycling. The disciplines are not all "races" or timed-speed events, as several disciplines test a competitor's various riding skills.-Motorcycle racing:...

.

No hands

This is how countersteering works when riding no-hands. To turn left, a rider applies a momentary torque, either at the seat via the legs or in the torso that causes the bike itself to lean to the right, called counter lean by some authors. The combined center of mass of the bike and rider is only lowered, of course. However, if the front of the bike is free to swivel about its steering axis, the lean to the right will cause it to steer to the right by some combination of gyroscopic precession (as mentioned above), ground reaction forces, gravitational force on an off-axis center of mass, or simply the inertia of an off-axis center of mass, depending on the exact geometry and mass distribution of the particular bike, and the amount of torque and the speed at which it is applied.

This countersteering to the right causes the ground contact to move to the right of the center of mass, as the bike moves forward, thus generating a leftward lean. Finally the front end steers to the left and the bike enters the left turn. The amount of leftward steering necessary to balance the leftward lean appropriate for the forward speed and radius of the turn is controlled by the torque generated by the rider, again either at the seat or in the torso.

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. No-hands riders may be able to keep a heavy bike centered in a lane and negotiate shallow highway turns, but not much else.

Bicycles

Conscious countersteering is generally not needed in normal bicycling, but it can be very useful—even potentially lifesaving—in emergency maneuvers, and is taught as the instant turn (a term coined by John Forester) in traffic cycling courses offered through the League of American Bicyclists

League of American Bicyclists

The League of American Bicyclists is a non-profit membership organization which promotes cycling for fun, fitness and transportation through advocacy and education....

. League certified instructors teach students to be prepared to make a sudden sharp turn to avoid, for example, being hit by a motorist who just passed them and then turned right, cutting the cyclist off. The instant turn is initiated by quickly jerking the bars to the left (the countersteer), which initiates the necessary lean to the right, and then turning sharply into the required turn to the right.

Motorcycles

Even more so than on a bicycle, mastering the technique of consciously countersteering is essential for safe motorcycle riding

Motorcycle safety

Motorcycle safety concerns many aspects of vehicle and equipment design as well as operator skill and training that are unique to motorcycle riding.-Accident rates:...

, and as a result is a part of the safe riding courses run by the Motorcycle Safety Foundation

Motorcycle Safety Foundation

The Motorcycle Safety Foundation is a United States national, not-for-profit organization, founded in 1973, and sponsored by the U.S. manufacturers and distributors of BMW, Ducati, Harley-Davidson, Honda, Kawasaki, KTM, Piaggio/Vespa, Suzuki, Triumph, Victory and Yamaha motorcycles...

 and the Canada Safety Council

Canada Safety Council

The Canada Safety Council is a national, non-profit, charitable organization dedicated to safety. They work to prevent deaths and injuries by promoting education and awareness across Canada.-External links:**...

. At the higher speeds that motorcycles commonly attain, it becomes increasingly impractical to steer by taking advantage of the minute and random corrections needed to maintain balance.

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.

To encourage an understanding of the phenomenon of countersteering, the phrase positive steering is sometimes used, and is summed up in a simplified way as "Push the right-hand bar to steer right; push the left-hand bar to steer left".

Typically, three wheelers like trikes and sidecar rigs do not countersteer. There are unconventional multi-tracked motorcycles like the three wheel Piaggio MP3

Piaggio MP3

The Piaggio MP3 is a tilting three-wheeled scooter from the Italian manufacturer Piaggio. It was first brought to market in 2006...

 which use complex mechanical linkages to lean the two front wheels in parallel, so that it is countersteered in the same manner as a two wheeled motorcycle. In contrast, the three wheeled BRP Can-Am Spyder Roadster

BRP Can-Am Spyder Roadster

The Can-Am Spyder is a Three wheeled motorcycle with a single rear drive wheel and two wheels in front for steering, similar in layout to a modern snowmobile. The Spyder uses an ATV-like chassis...

 uses two front wheels which do not lean, and so it steers like a car.

Other uses

The term counter-steering is also used by some authors to refer to the need on bikes to steer in the opposite direction of the turn (negative steering angle) to maintain control in response to significant rear wheel slippage.
The term is also used in the discussion of the automobile driving technique called drifting

Drifting (motorsport)

Drifting refers to a driving technique and to a motorsport where the driver intentionally over steers, causing loss of traction in the rear wheels through turns, while maintaining vehicle control and a high exit speed...

.

The Wright Brothers

Wilbur Wright explained countersteering this way:

External links

• Balance and Steering, by Tony Foale
• "No B.S. Machine" physical experimentation