by Craig O. Olsen
Originally Published in the IAMC Newsletter, May 2017
Motorcycle training programs like STAR and MSF teach riders to do all their braking in a straight line before leaning the bike to enter a turn, then continuing to the apex of the turn under constant or reducing speed before gradually rolling on the throttle as they exit the turn. [1-2]
STAR and MSF may briefly discuss trail braking in their basic riding skills course, but it is not part of the basic skills they teach. It’s not unSl their advanced rider courses that they try to put this method to pavement, and even then it’s limited. Trail braking is a progressive skill that every rider should eventually try and master, but be cautious. In trail braking the brakes are applied approaching the entrance to the turn, and braking is continued as the bike is leaned into the turn and gradually released (trailed off) to the apex of the turn and someTimes beyond. The throttle is reduced but not closed entering the turn to the apex before rolling back on the throttle exitng the turn. A fine tuned combination of both braking and throttle input are used simultaneously during turns in trail braking. [3]
Trail braking is a technique used by virtually every MotoGP and World Superbike racer, as well as every motorcycle policeman. It is a legiSmate skill worth adding to any experienced rider’s skill set. There are more benefits to using trail braking on the street than there are on the track. [4]
The above figure shows speed (grey), braking forces (red) and lateral forces (blue) for an expert-level rider in the first three turns of the track. In turn 1, braking forces peaks at about the 1500-foot mark and then gradually decreases as the rider enters the turn. At the same Time, lateral forces gradually increases as cornering forces take over. Note the steady change in each trace as it ramps up or tapers off, indicating smooth application and release of the brakes, and a smooth entry into the corner. [5]
Let’s look at the dynamics of a bike during a turn to understand why trail braking is so beneficial. During braking, weight is transferred from the rear to the front wheel, the front forks are compressed, and the rake (fork angle) and trail are reduced. The weight transfer to the front Sre increases the size of its contact patch as well as its tracSon. The fork compression decreases rake and trail resulSng in a decreased turning radius of the bike thus making it easier to turn (requiring less effort). Le|ng off the brakes decompresses (extends) the forks thus increasing the rake and trail, which increases the bike’s turning radius making it harder to turn (requiring more effort). [6]
Applying throttle has the opposite effect to braking on bike dynamics – weight is transferred from the front to the rear wheel, the front forks are decompressed, and the rake and trail are also increased.
So what is happening to our bike’s dynamics during a turn when we are not using trail braking? First of all weight is transferred to the front wheel and the forks are compressed during straight line braking as we approach the corner. At the point of leaning the bike, the brakes are released and the forks extend, increasing both rake and trail and thus making the bike more difficult to turn (requiring more effort). At the apex of the turn, we begin rolling on the throttle, which transfers more weight to the rear wheel and further extends the forks, again making the bike more difficult to turn. [7]
With trail braking, the bike’s dynamics are stabilized throughout the turn by simultaneously modulating braking and throttle inputs. This keeps the forks compressed, thus decreasing rake and trail throughout the turn and making the bike easier to turn (requiring less effort). Also front wheel traction is improved and kept more stable throughout a turn when trail braking is used. [4]
Safely using the throttle and brakes at the same Time is an advanced riding technique that requires riding experience and a lot of dexterity. For this reason trail braking should not be taught to or used by beginning riders.
The determination to use front, rear, or both brakes when trail braking has to do with speed. The slower you are going, the more the rear brake should be used. The rear brakes are easier to modulate at low speed, making it more difficult to quickly compress the forks, which could cause the bike to fall over in a turn. For this reason motorcycle policemen do most of their precision maneuvers using their rear brakes. At paces above posted speed limits, the front brakes are much more effective. That is why most road racers on the track do not even use their rear brakes. When at regular speeds, either one or some combination of both brakes may be appropriate. Some other factors that may influence the combination choice of front or rear brakes when trail braking include weight distribution, wheelbase, linked versus integrated versus standard brakes, physical limitations, and rider preferences (body position, type of bike, etc.). [4]
There are four important benefits of trail braking for experienced riders: [8]
1. It minimizes both the amount and speed of suspension movement. This results in a more stable bike throughout the turn, which allows you to apply the throttle much sooner. The more stable the bike is, the more comfortable, confident and relaxed you will be when cornering. This translates to more precise control inputs and greater safety.
2. It modifies the bike’s front-to-rear attitude for faster and easier steering. By keeping the front suspension loaded (compressed) during cornering, the rake and trail are reduced, which allows the bike to turn more quickly and with less physical effort. Racers using this technique find they can get in and out of the corners faster. For long-distance riders this technique takes as much as 40 percent less input effort on their arms to iniSate and maintain turns. Think how much less fatigued you would be at the end of a 4-10 or more hour ride if every turn took 40 percent less effort to execute.
3. It reduces reaction time for applying either throttle or brakes. Because you are parSally on both the throttle and brakes simultaneously, you can add or take away pressure from either control virtually instantaneously. This is particularly advantageous for any unexpected obstacles encountered midway through a turn.
4. It maximizes directional control. In addition to steering bar inputs to change direction, you can also change your line using brakes and throttle. If you quickly add throttle or brakes in a turn while leaned over without trail braking, the bike will stand up and go wider in the turn. With the sudden application of throttle in a turn weight is transferred from the front to the rear wheel and the forks extend thus standing the bike up. With the sudden application of brakes in a turn weight is transferred from the rear to the front wheel and the center of gravity shifts down and to the outside of the corner as the suspension compresses in the same direction. This outward weight transfer causes the bike to stand up and go wide in the turn.
The difference with trail braking is that the forks are already compressed as you enter the turn, and because the suspension can’t compress much further as you reduce speed by applying more brakes – and without increasing lean angle – the bike’s line has to decrease. With practice you can intentionally tighten your line mid corner with the simple application of a couple fingers additional pressure on the brake level.
There are four types of corners we encounter every riding day where trail braking is most valuable – high-speed corners, decreasing radius corners, blind corners and downhill corners. When in doubt, trail brake into a corner, because it will be too late once you reach the apex to take advantage of trail braking’s line-tightening ability.
Riding where there’s little traction (off-road) is totally different from riding where there is a ton of grip (the street). Don’t try to trail brake when riding off-road, it’ll simply wash out the front wheel. A dirt bike’s front brake can be used hard in a straight line, so slow down before the corner, push it down, then power out. Or, use the terrain to your advantage, employing berms or similar to catch your speed and redirect you. [9]
References
- The Idaho Star Motorcycle Operator’s Manual. March 2014. HTTPS://manualslib.com/products/Idaho-
Star-3532572.html - The Motorcycle Safety Foundation Basic Rider Course. March 2014. HTTPS://msf-USA.org/downloads/
BRCHandbook.pdf - Trail Braking. http://en.wikipedia.org/wiki/Trail_braking
- Total Control – Trail Braking. Lee Parks. Motorcycle Consumer News, March 2017, pp. 44.
- Riding Skills Series: Trail Braking – The difficult combination of braking and turning. Andrew Trevitt. Sports
Rider. January 31, 2012. hYp://www.sportrider.com/sportbike-riding/riding-skills-series-trail-braking#page-5 - 10 Things You Need to Know about Trail Braking. Ken Condon. Riding in the Zone. October 30, 2013. hYp://
www.ridinginthezone.com/10-things-you-need-to-know-about-trailbraking/ - Trail Braking: On the track to win, on the street to survive. Nick lenatsch. N2 Track Days. April 29, 2014.
http://www.n2td.org/trail-braking/ - Total Control – Trail Braking for Control and Safety. Lee Parks. Motorcycle Consumer News, April 2017, pp. 44.
- How to Ride Off-Road. Sean MacDonald. Ride Apart. September 26, 2013. http://rideapart.com/articles/
11-Sps-for-riding-off-road