Jarno Saarinen, a Finnish Grand Prix motorcycle racer who won the world 250 GP Title in 1972, is the rider on the world stage credited first for dragging a knee or using the “knee out” riding style. “King” Kenny Roberts Sr.’s famous tuner Kel Carruthers brought this technique to the attention of his rider, which Kenny developed and soon popularized in the United States. The art of dragging a knee has evolved, and as tire and motorcycle technology has progressed over the past 40 years, riders like Marc Marquez have brought the concept to an entirely new level.
While many riders will never be able to drag their elbow like Marquez, dragging a knee (or the “knee out style”) is a technique that virtually every experienced track rider can utilize. Getting a knee down is not only a popular goal for track riders but also an important one for achieving proper riding technique. In this article, we will touch on some of the reasons why riders want to hang off of the motorcycle. And then explore in further detail the importance of the proper use of the knee in this process.
Motorcycles must lean to turn with any amount of speed. As bikes (or any vehicle for that matter) travel in a circular path, there is a centrifugal force that always works in the opposite direction of the radius of the circle. An object traveling in a circular path at a constant velocity is always accelerating towards the center of the circle. This centrifugal force of this acceleration is determined by the equation MV2/R. Where M is mass, V is velocity and R is the radius. On a motorcycle, this force is always acting to make motorcycle stand up. In order to balance this force, the motorcycle must lean in order to use the force of gravity (weight) to balance this acceleration.
(See Diagram A). The greater the speed, the more the motorcycle has to lean to counteract this centrifugal force. From a physics standpoint, all of these forces act through the center of gravity (CG) of the object traveling the circle. For a motorcycle, this is the composite CG of the motorcycle and
rider together (shown as the orange dots in Diagram B). Since in most cases the rider makes up about 1/3 of the overall weight of the package, the rider has a significant effect on the location of the CG. When comparing the red rider to the green rider, you can see that when a rider gets off the seat and moves to the inside of the motorcycle, the CG that rider and the moves to the inside as well. The advantage of this technique becomes quickly apparent. As we can see that when the rider moves to the inside, the resulting CG (again, in orange) as if the motorcycle increased in lean angle while the tire itself remains upright (the yellow dot does not move). This provides quicker turning with less risk, faster lap times, and many significant handling advantages we have discussed in past articles.
The main challenge that riders find with this technique comes because they are no longer sitting directly in the seat and must find a way to support their body weight. The most common mistake that riders make is to use their inside arm for this extra support. The drawbacks to supporting your weight with your inside hand are well documented and include reduced traction, decreased feedback and increased front end motion. After teaching riders on the track with the Penguin School for nearly 20 years, I feel that this is the number one cause for rider issues on the race track. The importance of eliminating this practice cannot be overstated.
With this in mind, where does the knee come into play? There are all kinds of advantages to using your inside knee while riding. Including advanced techniques that allow riders to utilize the knee as a lean angle gauge and to help save front end slides. However, the most basic advantage is one that applies to riders of all skill levels. To act as a support for your body weight to allow riders to hang off the motorcycle and leave their arms relaxed.
When riders start to hang off the bike, the most important step to give yourself the ability to use the inside knee is to leave your hips square to the motorcycle. When riders rotate their hips around the tank, the inside knee tends to point forward. As opposed to the inside of the corner. In order to truly understand how much this affects you, get on your motorcycle while on a sturdy rear stand in the paddock. Have a friend support the bike. Next, get off the tank as far as you reasonably can (slightly more than you do on the track) while making sure your hips are square, knee is to the inside and chin is over the inside fork tube. Your spine should be parallel to the axis of the motorcycle.
Finally, take your hands off of the bars and then slowly point your knee towards the front of the motorcycle until you start falling off the inside of the bike (and you will). Of course, if you point your knee forward (against the motorcycle) on the track you will not immediately fall off the bike. However, you will be forced to transfer force into the bars to support your body weight and deal with the reduced traction and feedback that comes along with it. When you point your inside knee into the turn, you are putting yourself in the best possible position to support your body weight with your legs and to relax your arms. Once you have achieved this first step, the final piece of the puzzle is to firmly secure your outside leg to the tank, firmly locking your body into place and allowing your hands to fully relax. With this important baseline, you will start riding faster with more confidence and before you know it you’ll be dragging a knee and ordering a spare set of knee pucks!
Until next time… Ride fast, ride safe.