Watch a modern MotoGP, Moto2 or World Superbike race with a casual fan and you can be certain there is one question they will ask you: "Why are they waving their legs about like that?" Many theories have been offered, often directly contradicting each other. For example, several years ago, I suggested that the leg wave is entirely mental. Earlier this year, the Australian motorcycle coaching organization MotoDNA described the possible role which aerodynamics play, the exposed leg helping to create more drag. Much has been said, yet it seems impossible to settle the argument one way or another.
Asking the riders to explain does not help much. It is a question I and other journalists have asked of many different riders, including Valentino Rossi, Casey Stoner, Cal Crutchlow, and Dani Pedrosa. Their answers always boil down to the same thing: "It just feels natural," they say. An interesting response, perhaps providing an insight into how deeply racers have internalized so much of the physical part of their riding, but not doing much to help explain the phenomenon.
To attempt to get to the bottom of this mystery, I turned to some of the best minds in the MotoGP paddock. For an explanation of the physics behind the leg wave, I asked Monster Tech 3 Yamaha crew chief and technical guru Guy Coulon, while for further insight from the point of view of an observer and ex-rider, I spoke to Wilco Zeelenberg, team manager of Jorge Lorenzo - the one current MotoGP rider who does not dangle his leg while riding.
The answer, said Coulon, was not simple. "This is quite difficult to answer. We can believe that when you put your legs in this position on braking, the center of gravity is more inside and you can keep straighter on braking for a longer time." So was the point of the leg wave to move the center of gravity of bike and rider? "I think so, because on braking, you have to be quite straight on the bike, so you cannot move your shoulder or anything else," Coulon replied.
Coulon accepted that the mental aspect could be one reason which riders dangle their legs. Could it be that seeing other riders do it, and believing it conferred an advantage, other riders start to copy the behavior? "Yes, of course," Coulon agreed, but more physical aspects also played a role. "But maybe also because of bike geometry, and the kind of tire being used, and what they are able to do on corner entry, so step-by-step they can use this sticking the leg outside," the Frenchman added. "But for me, it's really complicated to explain." He had seen the maneuver become ever more prevalent among riders, Coulon said. "Like everybody else, I can see step-by-step, one rider, two riders, and more and more riders are using this style. But themselves, they don't know really why, and sometimes they don't feel they are doing it."
In a previous article, I argued that Valentino Rossi was one of the first riders to start to use his leg off the pegs on a regular basis, and that the fact that he saw other riders copying him gave him a confidence boost and a mental advantage. Though Coulon emphasized that he believed there were sound physical reasons for the leg wave, he agreed that riders tend to watch each other closely and copy each other. "I think it is similar to when the first riders started to use sliders on the knees. One guy started to do that because it helped him control the slide, and it was like a sensor to check the lean angle, then after this, everybody started to use this style," Coulon explained. "But I think [dangling] legs outside can be used for better stability, and to keep the center of gravity center more inside in the corner where the rider is going, to keep the bike straighter for longer, to keep it in the same position."
Was there any evidence in the masses of data collected after every session which might help to explain exactly what was happening? "I think it's a bit complicated to see on the data," Coulon said.
"Maybe if someone was focused on this and tried to find something in the data, they could. We didn't try. But for sure, using data, it would be possible to test with a test rider, for example, and we could understand with the same speed, the same deceleration, the same line, with the legs [dangling] outside or not, if the angle is same or different. But for sure angle would be different." The question is whether a test rider would even be capable of performing the test, as the styles required are so very different. "It's not so easy to ask one rider to change his style only to compare the data," Coulon added. "It seems they are doing it without thinking, finally." Mainly, it was a question of balance, he said, the leg being used "like a tightrope walker uses his pole to keep his balance."
The one rider who does not use the leg wave is Jorge Lorenzo. "Yes, but Lorenzo is very stable on the brakes, because of his own style," Coulon explained. "Because he is really really smooth everywhere, so we never see him with real jumping on the brakes, he controls everything very smoothly, he brakes, releases the brakes very gently. and early. He can carry a lot of corner speed, then also opening [the throttle] he is very smooth. It seems he needs to find less extra stability, because he is already stable because of his own personal style. He always looks very clean."
Wilco Zeelenberg agrees. As Jorge Lorenzo's team manager, part of his role is as acting as rider coach and helping identify areas where the Spaniard is having problems. As part of this, he spends a lot of time at track side watching Lorenzo, and assessing what is going on. Zeelenberg agrees with Coulon, it is the smoothness of Lorenzo's style which precludes him taking his feet of the pegs. "He's not really an extremely late braker," Zeelenberg said. "He wants to keep his bike as stable as possible, as soon as you take your leg off the peg the bike begins to wander, and you have to search for stability. It looks to me like they [the riders who dangle their legs] are looking for stability this way, because they have so much pressure on the front wheel. They are trying to gain some control over the bike, to keep it stable, but [Jorge] never lets it get that far."
So Lorenzo is creating stability in a different way? "He brakes a little earlier, but in a different way, so he never arrives at the corner with the bike on its front wheel, which makes it want to go all over the place, which makes you lose control. Your foot is a good lever to handle this." Lorenzo arrives at the corner with the bike already under control and at the right speed, Zeelenberg explained.
As a rider, Zeelenberg said, he had never taken his leg off the pegs, so he could not speak from personal experience. But he could see how it seems to work for some riders, from the time he has spent at track side watching. "It seems to have a limited advantage. So I think for some riders, especially really late brakers, it helps," Zeelenberg explained. "When you brake really, really late, your heart rate goes up a lot, your pulse starts really racing, and you stiffen and cramp on the bike. That's no good. By throwing your leg off the bike, you relax again, which makes it possible for you to stick the bike into the corner."
"The leg helps with this," Zeelenberg continued, "because you can throw the bike to the left a lot more easily. If you're braking, and thinking 'Shit! I'm too late,' at the moment the riders get that 'shit!' feeling, that's the moment they take their foot off the peg. They realize that at the moment they have that feeling, and stick their leg out, they can still make the corner." It is a way of breaking through their own mental fear of braking too late, Zeelenberg explained. "Everyone has a sort of mental barrier at which point you think 'Shit, I'm not going to make it," at that point, you cramp up even more, and then you won't make the corner." So it is a way in which riders force themselves to loosen up again, to take away the cramped stiffness? "Yes. But also, it's left-handed corners. None of them stick their right legs out if there's a left turn coming. So it definitely has something to do with balance, but also with forcing the bike into the corner at the moment you stick your leg out."