Trail braking

Trail braking into a corner at Miller Motorsports Park

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.

Usage in motorcycling

In applying this technique, motorcycle riders approach turns applying both front and rear 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, this gives more traction because the front tire is forced into the pavement under the weight of the vehicle. 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 want to lean and change direction. Thus, trail braking can be used as method used to help the motorcycle change direction.

Additionally, decreasing speed decreases the motorcycles cornering radius, while, conversely, accelerating while turning increases the motorcycles cornering radius. 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.

Finally, trailing off the brakes while entering blind or tight corners allows the rider to slow if something unexpected blocks the riders 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. However, applying the brakes after the motorcycle is already leaned over can be exceedingly risky because there is, relatively, very little weight over the front tire increasing the chances of losing traction.

This technique is commonly used when racing, but can enhance control and add more evasive options for street riders making it very worthwhile to learn or at least understand.

Risks in motorcycling

There is a high degree of inherent risk with trail braking; 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 a high degree of finesse from the motorcycle operator and has a very steep learning curve for riders wishing to learn and adopt this technique.

As motorcycles have a pronounced tendency to "stand up" when brakes are applied in a turn, the rider must initially counter that force with corresponding steering inputs. The handle bar pressure required, at this point, to hold the bike in the turn is one of the classic contributing causes of trail braking crashes even with pro riders.

For a discussion of how this applies more force to the front tire and how much, see Bicycle and motorcycle dynamics.

Controversy in motorcycling

It is generally agreed upon that the safest way 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. Opponents of trail braking claim that because of the steep learning curve trail braking is or should be an exclusively race track or racing technique. However, proponents of trail braking believe that knowing and understanding how to slow while entering a corner gives the rider a greater safety margin, particularly in blind, decreasing radius or downhill corners.

Two highly accredited motorcycle riding schools are effectively split on the implementation of trail braking. Keith Code, founder of the California Superbike School teaches that the only way to turn a motorcycle is with countersteering and that riders should accelerate throughout the corner for optimum motorcycle stability. Freddie Spencer, founder of Freddie Spencer's High Performance Riding School teaches that trail braking should be used in most every corner as a means to make the motorcycle change direction, advocating that trail braking gives the rider more control and significantly increases rider safety.

Usage in four wheel vehicles

In 4-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 transfer 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.

Usage in racing

A drift-inducing technique called "the brake drift" is used in racing, involving a series of light trail-braking pulses (usually 2 or 3), followed by a momentary full-force braking and sharp releasing of the 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.

References

• Ienatsch, Nick (2003). Sport Riding Techniques: How to Develop Real World Skills for Speed, Safety and Confidence on the Street and Track. David Bull. ISBN 1-893618-07-2.

• Code, Keith (1993). A Twist of the Wrist - Volume II. Code Break. ISBN 0-3650450-2-1. {{cite book}}: Check |isbn= value: checksum (help)

• Brian Beckman Ph. D. "Physics of Racing -- Trail Braking". Retrieved 2006-12-31.

• Efstathios Velenis, Panagiotis Tsiotras and Jianbo Lu. "Modeling Aggressive Maneuvers on Loose Surfaces: The Cases of Trail-Braking and Pendulum-Turn" (PDF). Retrieved 2008-11-09.

External links

• Video Footage of Trail Braking with a Kart