Trail braking
Encyclopedia
Trail braking is a motorcycle riding and driving technique where the brakes are used beyond the entrance to a turn and are gradually released up to the point of apex.
In a broader scope, trailing off the braking pressure either while straight line braking or, as above, after turn in has begun, allows for a less abrupt and more accurate final corner entry speed adjustment. Some corner entries, such as decreasing radius turns, are more adapted to the leaned over trail braking technique. In turns where a quicker steering action is more applicable, trailing the brake while turning in is unnecessary.
riders approach turns applying front brakes to reduce speed. As they enter the turn, they slowly ease off the brakes, gradually decreasing or trailing off the brakes as motorcycle lean increases. This is done for several reasons.
First, it gives more traction because the downward force on the front tire
is increased by load transfer. Second, as the brakes are applied and the weight shifts forward, the forks are compressed. The compression of the forks changes the motorcycles steering geometry
, decreasing stability in a way that makes the motorcycle more apt to lean and more quickly change direction. Third, decreasing speed decreases the motorcycle's cornering radius
. Conversely, accelerating while turning increases the motorcycles cornering radius.
Fourth, trailing off the brakes while entering blind or tight corners allows the rider to slow if something unexpected blocks the rider's path. Because the motorcycle is already on the brakes and the front tire is getting additional traction from already slowing, the rider can slow even more with very little risk, depending on surface conditions. However, applying the brakes after the motorcycle is already leaned over can be exceedingly risky depending on surface conditions and lean angle.
Traditionally, trail braking is done exclusively with the front brake even though trailing the rear brake will effectively slow the motorcycle, also decreasing the turning radius. If the motorcycle is leaned over, forces from the front brake and the deceleration causes the motorcycle to yaw (lean), while use of the rear brake generates a torque that tends to align (straighten) and stabilize the motorcycle.
The rider's ability to correctly choose his turn in, apex and exit points reduces or eliminates the need for prolonged trailing of the brakes into turns. This technique is commonly used when racing, but can enhance control and add more evasive options for street riders.
Basic RiderCourse teach that the safest way for a beginning rider to approach a corner on a motorcycle is by performing all of the slowing before the entrance of the turn, discouraging the use of any brakes while the motorcycle is leaned over. The argument against trail braking on the street, at least for beginners, is that the steep learning curve of trail braking makes it appropriate only for the race track. The benefit of learning trail braking to the street rider is that knowing and understanding how to slow while entering a corner gives a greater safety margin, particularly in blind, decreasing radius or downhill corners.
Prominent motorcycle authorities do not disagree on the technique of trail braking. Keith Code
, founder of the California Superbike School teaches that the only way to effectively and accurately direct and turn a motorcycle is with countersteering
, in his 1983 book A Twist of the Wrist he states "To tighten a turn and increase your lean angle, you must countersteer again". However, Freddie Spencer
, founder of the now defunct Freddie Spencer's High Performance Riding School as well as Nick Ienatsch, author of the 2003 book Sport Riding Techniques and chief instructor of Yamaha Champions Riding School
argue that trail braking should be used in nearly every corner as a means to help the motorcycle change direction, stating that trail braking gives the rider more control and significantly increases rider safety.
Spencer and Ienatsch agree with the physics of angular acceleration
and correctly note that the slower any vehicle is going, the tighter the radius of the corner it can navigate. This is seemingly opposed to Code's writing that, with no change of speed but a tightening in radius, only countersteering can affect the motorcycle's direction. Nevertheless, there is no real contradiction here. Spencer points out that for every radius, motorcycle, and rider combination there is a maximum speed at which the turn can be navigated without exiting the road or suffering a low side crash. Code is saying that as long as this maximum speed is not exceeded, counter steering is the only way to increase lean angle and decrease the radius of ones turn. If Code's method is employed at a speed higher than Spencer's maximum, then a low side crash likely ensues, but if Code's method is not employed as the bike approaches the edge of the road or track then the bike will exit the road or track.
towards the front tires, thus increasing their traction and reducing understeer. It works best in light vehicles that have their brake bias to the front.
In order to be properly performed, the driver must have excellent sense of the vehicle's behavior and be able to keep the braking effort within very tight limits. Excessive braking effort may result in the vehicle heavily understeering, or - if the brake bias is set to nearly neutral - in the rear wheels locking, effectively causing the vehicle to spin as in a handbrake turn
.
Once a driver has mastered trail braking, it can help enter the corners at higher speeds, or avoid an accident if the driver has entered a corner at a speed exceeding the vehicle's (or driver's) capabilities.
More physics behind using trailbraking for 4-wheel vehicles can be found in
.
technique called "the brake drift" is used in racing, involving a series of light rear brake trail-braking pulses (usually 2 or 3), followed by a momentary full-force rear braking and sharp releasing of the rear brakes. Mastering continuous trail braking as used under road conditions is a prerequisite for learning brake drifting. This is one of the most used drifting techniques in rally racing
because - if done properly - allows the driver to enter and exit the corner with full throttle.
Depending upon cornering situations, techniques like trail braking can be used to maintain more speed upon entry of a corner, and attaining more grip while turning into the corner, and has an effect on apex selection. In this technique, brake pressure is applied slightly later than usual upon deceleration, and is maintained during steering input, sometimes all the way to the apex. The action of braking causes a weight transfer in the vehicle, shifting more weight from the rear of the car forward to the front tires, increasing the normal force on them and in turn increasing the amount of traction the front (steering) wheels have. Because of the characteristics of weight transfer, this technique causes weight to be shifted away from the rear of the car, resulting in lower rear traction, and can be used to induce oversteer in some cases.
In a broader scope, trailing off the braking pressure either while straight line braking or, as above, after turn in has begun, allows for a less abrupt and more accurate final corner entry speed adjustment. Some corner entries, such as decreasing radius turns, are more adapted to the leaned over trail braking technique. In turns where a quicker steering action is more applicable, trailing the brake while turning in is unnecessary.
Motorcycling
In applying this technique, motorcycleMotorcycle
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...
riders approach turns applying front brakes to reduce speed. As they enter the turn, they slowly ease off the brakes, gradually decreasing or trailing off the brakes as motorcycle lean increases. This is done for several reasons.
First, it gives more traction because the downward force on the front tire
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
is increased by load transfer. Second, as the brakes are applied and the weight shifts forward, the forks are compressed. The compression of the forks changes the motorcycles steering geometry
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...
, decreasing stability in a way that makes the motorcycle more apt to lean and more quickly change direction. Third, decreasing speed decreases the motorcycle's cornering radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
. Conversely, accelerating while turning increases the motorcycles cornering radius.
Fourth, trailing off the brakes while entering blind or tight corners allows the rider to slow if something unexpected blocks the rider's path. Because the motorcycle is already on the brakes and the front tire is getting additional traction from already slowing, the rider can slow even more with very little risk, depending on surface conditions. However, applying the brakes after the motorcycle is already leaned over can be exceedingly risky depending on surface conditions and lean angle.
Traditionally, trail braking is done exclusively with the front brake even though trailing the rear brake will effectively slow the motorcycle, also decreasing the turning radius. If the motorcycle is leaned over, forces from the front brake and the deceleration causes the motorcycle to yaw (lean), while use of the rear brake generates a torque that tends to align (straighten) and stabilize the motorcycle.
The rider's ability to correctly choose his turn in, apex and exit points reduces or eliminates the need for prolonged trailing of the brakes into turns. This technique is commonly used when racing, but can enhance control and add more evasive options for street riders.
Risks
There is risk with trail braking because excessive use of the front brake can result in a loss of grip as the tire's adhesion is split between braking and cornering forces. Effective trail braking requires finesse from the rider, which can be difficult to learn.Controversy
Guides such as the Motorcycle Safety FoundationMotorcycle 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...
Basic RiderCourse teach that the safest way for a beginning rider to approach a corner on a motorcycle is by performing all of the slowing before the entrance of the turn, discouraging the use of any brakes while the motorcycle is leaned over. The argument against trail braking on the street, at least for beginners, is that the steep learning curve of trail braking makes it appropriate only for the race track. The benefit of learning trail braking to the street rider is that knowing and understanding how to slow while entering a corner gives a greater safety margin, particularly in blind, decreasing radius or downhill corners.
Prominent motorcycle authorities do not disagree on the technique of trail braking. Keith Code
Keith Code
Keith Code is a former motorcycle racer,writer, and founder of the California Superbike School.He has been called "arguably the best known and most successful on-track motorcycle instructor in the world".-Rider training:...
, founder of the California Superbike School teaches that the only way to effectively and accurately direct and turn a motorcycle is with countersteering
Countersteering
Countersteering is the technique 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...
, in his 1983 book A Twist of the Wrist he states "To tighten a turn and increase your lean angle, you must countersteer again". However, Freddie Spencer
Freddie Spencer
Freddie Spencer , known by the nickname Fast Freddie, is an American former World Champion motorcycle racer. Spencer is regarded as one of the greatest motorcycle racers of the early 1980s.-Biography:...
, founder of the now defunct Freddie Spencer's High Performance Riding School as well as Nick Ienatsch, author of the 2003 book Sport Riding Techniques and chief instructor of Yamaha Champions Riding School
Yamaha Champions Riding School
Yamaha Champions Riding School is a motorcycle training program based at Miller Motorsports Park in Tooele, Utah. It is the evolution of Freddie Spencer's defunct High Performance Riding School...
argue that trail braking should be used in nearly every corner as a means to help the motorcycle change direction, stating that trail braking gives the rider more control and significantly increases rider safety.
Spencer and Ienatsch agree with the physics of angular acceleration
Angular acceleration
Angular acceleration is the rate of change of angular velocity over time. In SI units, it is measured in radians per second squared , and is usually denoted by the Greek letter alpha .- Mathematical definition :...
and correctly note that the slower any vehicle is going, the tighter the radius of the corner it can navigate. This is seemingly opposed to Code's writing that, with no change of speed but a tightening in radius, only countersteering can affect the motorcycle's direction. Nevertheless, there is no real contradiction here. Spencer points out that for every radius, motorcycle, and rider combination there is a maximum speed at which the turn can be navigated without exiting the road or suffering a low side crash. Code is saying that as long as this maximum speed is not exceeded, counter steering is the only way to increase lean angle and decrease the radius of ones turn. If Code's method is employed at a speed higher than Spencer's maximum, then a low side crash likely ensues, but if Code's method is not employed as the bike approaches the edge of the road or track then the bike will exit the road or track.
Driving
In four wheel vehicles trail braking pertains to using the brakes past the corner entrance (as opposed to the normally taught practice of releasing the brakes before starting the turn). This practice is used for creating weight transferWeight transfer
Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: the change in load borne by different wheels of even perfectly rigid vehicles during acceleration, and the change in center of mass location relative to the wheels because of...
towards the front tires, thus increasing their traction and reducing understeer. It works best in light vehicles that have their brake bias to the front.
In order to be properly performed, the driver must have excellent sense of the vehicle's behavior and be able to keep the braking effort within very tight limits. Excessive braking effort may result in the vehicle heavily understeering, or - if the brake bias is set to nearly neutral - in the rear wheels locking, effectively causing the vehicle to spin as in a handbrake turn
Handbrake turn
The handbrake turn is a driving technique used to deliberately slide a car sideways, either for the purpose of negotiating a very tight bend quickly, or for turning around well within the vehicle's own turning circle....
.
Once a driver has mastered trail braking, it can help enter the corners at higher speeds, or avoid an accident if the driver has entered a corner at a speed exceeding the vehicle's (or driver's) capabilities.
More physics behind using trailbraking for 4-wheel vehicles can be found in
.
Racing
A drift-inducingDrifting (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...
technique called "the brake drift" is used in racing, involving a series of light rear brake trail-braking pulses (usually 2 or 3), followed by a momentary full-force rear braking and sharp releasing of the rear brakes. Mastering continuous trail braking as used under road conditions is a prerequisite for learning brake drifting. This is one of the most used drifting techniques in rally racing
Rallying
Rallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...
because - if done properly - allows the driver to enter and exit the corner with full throttle.
Depending upon cornering situations, techniques like trail braking can be used to maintain more speed upon entry of a corner, and attaining more grip while turning into the corner, and has an effect on apex selection. In this technique, brake pressure is applied slightly later than usual upon deceleration, and is maintained during steering input, sometimes all the way to the apex. The action of braking causes a weight transfer in the vehicle, shifting more weight from the rear of the car forward to the front tires, increasing the normal force on them and in turn increasing the amount of traction the front (steering) wheels have. Because of the characteristics of weight transfer, this technique causes weight to be shifted away from the rear of the car, resulting in lower rear traction, and can be used to induce oversteer in some cases.
External links
- Video Footage of Trail Braking with a Kart