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More on the Dangling Foot
Brian Childree is an RRX contributor and amateur racer in the Salt Lake City area.
At the end of last month, RRX intern Jesse Cecil posted a blog about his musings on the evolution of riding style (check it out here). JC’s blog began at the beginning, stopped off at the ’60s and ’90s, and ended with observations of a new trend in road racing style: Valentino Rossi’s “leg-dangle,” first seen around the advent of the 800cc MotoGP machines and since adopted by many of the series’ front-runners. The question of whether the leg-dangle is style, substance, or both (i.e. whether it actually benefits the riders) has provoked some great discussions and debate through the last few weeks, and RRX contributor Brian Childree is the latest to weigh in.
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Regarding the mysterious dangling MotoGP foot….
First, we need to have an understanding of how current geometry setup on a MotoGP bike works, particularly ride height. Teams are going to a bike with a slightly higher center of gravity than what was previously used (we’re talking millimeters, not centemeters). The reasoning is to generate more weight transfer, both front and rear, because if there is more load on the tire, it will flatten out more and give a greater contact patch. which means the rider can brake harder still.
The problem with a high center of gravity is that on really hard, straight-line braking, the weight transfers so much that the rear tire wants to lift off the ground. To combat this, riders have began to compensate for the high center of gravity with a geometry tool that is dynamic: their bodies. By dangling their foot close to the ground, they are effectively lowering the bikes center of gravity through one particular section (i.e. straight-line braking), and then returning the bike to its normal center of gravity for the rest of the track.
A higher center of gravity is also beneficial in other areas of riding, such as quick transition sections where the bike goes from full lean on one side to full lean on the other. A lower center of gravity can feel sluggish in transition and almost too stable. It becomes a matter of finding a happy medium at that point.
One question I’ve been asked before is why the teams don’t just run softer suspension to allow the bike to transfer weight easier via a lower center of gravity, and I think that comes down to rider preference. I would venture to guess that Rossi was the first to begin dangling his foot partially because he is notorious for running an extremely stiff suspension and tire setup. It was rumored that when he ran Michelins, his tire carcasses were sometimes up to 30 percent stiffer than any other rider’s in MotoGP, including his teammate’s.
Hope you find this stuff as interesting as I do.
This came out today as well, regarding the Rossi Leg Wave…
http://www.motogpmatters.com/opinion/2009/07/22/the_truth_behind_the_rossi_leg_wave.html
My guess is that they use it like a g-force sensor. They let their leg dangle out then brake super hard, their foot gets thrown forward and it gives them a better idea of how hard they are hitting the brakes. I think Rossi is useing it to block the inside line and I’m tired of seeing it. Lorenzo is gonna run right through Rossi’s leg one day.
All this speculation on the leg wave is getting pretty funny. G-force sensor, or to lower the center of gravity??? please… I would say it’s something that just feels right to the rider using it. Ask anyone who races or used to race like myself that the way the bike feels or your own riding style feels has a lot to do with good lap times. All these supposed reasons people are coming up with makes me laugh.
For sure it “feels right” to the riders who use the move, but there’s undoubtedly a reason why that’s the case. Considering the pervasiveness of the leg-dangle among top riders in one class within one series (riders whose machinery follows similar trends, the same rules, and is miles away from that of other championships’ bikes), it seems pretty logical that the action is offering concrete, measurable benefit specific to the way modern MotoGP bikes want to be ridden.
I find everyone’s theories on the subject really engaging.
The leg dangle is obvious to anyone that is a fast rider (both tires howling on corner entry and into the apex.) It works like the tail of a large wild cat… It is a ballast and a balancing mechanism (which is pretty much what the author of this blog is alluding to.) In addition to allowing harder braking, it is also a safety measure, because it allows the rider to cross the limit (within reason) of what the tires will hold going into the corner. Once the limit is mildly passed, the leg can be used to bring the bike back from the brink by further extending it, or moving it towards the front or back wheel to help balance the load on the tires.
A similar use of the leg off is when riding a deeply rutted track in motocross. Often the bike chooses to go where it likes when at speed, and a kick of the leg off to the side of the bike can bring it in line with a rut that otherwise would end up as a nasty cross-rutted disaster if the bike was corrected by steering input alone (ie: trying to counter steer to align with a deep rut and entering the rut with the wheel cocked and your body not centered over the bike.)
I have used the leg off technique my entire two-wheeled career and it has saved my butt many times. It is as natural as taking your feet off the pegs during a vicious tankslapper. It also is slightly related to the natural tendency for riders to spread their legs during a “flying W” (being pitched or bucked over the front of the handlebars,) because by varying the extension of your legs, you can offset side forces that otherwise may diminish your ability to brace against the handlebars.
I believe Rossi is playing dumb and dodging the answer, or possibly he feels he cannot adequately explain himself in English, so he doesn’t bother to really answer when question about the leg dangle.
CW Technical Editor Kevin Cameron asked Valentino Rossi about the “leg dangle” at Mazda Raceway Laguna Seca this past July. Here is Rossi’s response:
“I put one foot out when I brake very hard. I feel it is possible to brake deeper. But I don’t know if this is true. The first time, I didn’t decide, ‘Now I take my boot off the footpeg to brake harder.’ It came naturally to me. Now, I see also a lot of different riders doing the same thing.”
Additional excerpts from the Rossi interview can be found here: http://www.cycleworld.com/article.asp?section_id=43&article_id=1627
I’ve got to agree with Pervy 100%. I’ve employed the leg out in a few instances, just out of instinct and necessity. If the entry speed is preceved too high the braking goes harder and deeper into the turn, the leg goes out to help appose the forces and make the turn in.
I’ve ridden motocross for over 40yrs, and motards and sportbikes for 10 yrs. I disagree with Keith not giving the 30 lbs leg any credit. In the dirt there is a huge difference between hanging the foot by the engine case or by the front axle. The weigh transfer to the front tire is real.
I am no professional instructor, but when I’ve pushed too hard and stuck the leg out because every sense in my mind and body tells it to and it results in living another day, I’m a believer.
Those guys are driving so hard into the turn they hang the leg in a controlled manner. Unlike my personal panic situation, however the results are the same.