Why do MotoGP riders dangle their leg out under braking?

There are mainly three reasons why MotoGP riders put their leg out during a braking section: to increase air resistance, to make it easier to enter a corner, and to prevent an inside overtake by a rival. A fairly new riding technique, introduced by Valentino Rossi, that everyone is now adopting.

As fans and insiders know well, evolution in the field
MotoGP
is not measured solely in technical advances. New motorcycles, new circuits and new technological equipment have always conditioned the progression of the riding style and technique of the riders, who are always looking for the perfect balance with the mechanical means and the highest possible performance.

Torso inside the fairing, knee on the ground and now the celebrated “leg out” are only the most conspicuous modifications to a way of being on a motorcycle that has changed profoundly in recent years.

Valentino Rossi and the leg out

It was probably Valentino Rossi who was the first to introduce this new riding technique, in 2005 at Jerez during his now-famous overtaking of Sete Gibernau.

Arriving at the last corner just a few meters from his rival, the Doctor attempted a desperate overtaking maneuver, with a furious braking move that allowed him to overtake the then Movistar rider and triumph on the Spanish circuit. Either by instinct or by incredible calculation skills, during braking, Rossi threw his inside leg over the motorcycle platform, leaving it in midair at the apex.

In one of the most compelling moments in modern two-wheel history, the rider from Tavullia had once again rewritten the great book of motorcycling.

Soon a large number of pilots began to perfect the maneuver, gaining a noticeable advantage from it and studying its effects and characteristics, calibrating the amplitude of the movement and the proper timing for sticking out and then withdrawing the leg.

It is difficult, if not impossible, today to find a MotoGP rider who does not use this technique, exasperating it in hard braking or only hinting at it in slower changes of direction. There are three reasons why this maneuver is so effective, the pilots themselves tell us, two largely related to physics and one to closer competition.

Aerodynamic Brake

One of the reasons why MotoGP riders put their leg out under braking is to create aerodynamic drag by pitting more surface area against the airflow that hits them at very high speeds.

In this case, the leg on the outside of the rider’s silhouette becomes like a sail or aileron, which collects air, slowing the rider and his steed as he approaches the turn. That’s what happens to drag racing cars, which at the end of the straight throw a large canvas parachute behind them, or like airplanes that to slow down on the runway sprout large flaps from their wings to smash into the airflow.

Clearly, this “parachute” effect offers limited slowing capabilities, but all is more than useful when looking for the last possible inch to come off the gas and stick to the brakes. Then again, as the saying goes, the secret to success is to be “first on the throttle, last on the brakes.”

Center of gravity, centrifugal force and moment of rotation

What happens to a motorcycle that faces, at maximum lean, a curve at very high speed is a small miracle of physics. Intertwining within a few thousandths of a second are dozens of conflicting forces pointing in different directions. The balance between these forces gives the perfect maneuver and an incredible travel speed. Conversely, when something does not work between these forces, there are only two options: either go down or go long.

In a human being, each leg corresponds to about 20 percent of body weight. A considerable mass which, for an individual weighing about seventy kilograms corresponds to about fifteen kilograms.

The skillful use of such a weight can greatly affect the displacement of the center of gravity and the consequent resistance to the centrifugal force that asks the bike-rider pair to move outward out of the curve. In fact, moving your leg inside the bend, away from your body, means shifting your entire center of gravity, making it easier to enter the bend.

At the same time, due to the air resistance described above, the leg and pelvis are rotated slightly toward the opposite direction of motion, creating a moment of rotation that, again, makes it slightly easier to “curve” the bike.

Preventing overtaking

Largely more pragmatically, many drivers credit the outside leg with the great merit of preventing or making overtaking from the inside more difficult. Especially in today’s highly competitive MotoGP, with braking as one of the points where most overtaking occurs, the inside of the corner is one of the most popular spots to try to overtake an opponent.

To extend the leg under braking is to increase the area of defense and provide an extra obstacle for the pursuing rider to circumvent.

The leg out under braking between myth and legend

It is hard to say whether all three points listed above are actually true or whether, as the less dreamy want, there is much fashion in this spectacular and daring maneuver. In short, it is difficult to distinguish fantasy from scientific evidence and to understand what the lap time outcomes would be if someone stopped throwing out his leg and held it firmly on the side of the bike.

Certainly, if all the twenty-two fastest drivers in the world adopt this technique, some advantage will be there, even if only psychological, as a kind of very special placebo effect. It remains that, just like the knee to the ground, the leg off under braking-better even with the boot lightly touching the asphalt to make a wisp of smoke rise-has immediately become a great public favorite and a symbol of this wonderful sport. Then, if only for that, it would be worth it.