Hi all. Forgive the long post.

First, a short intro. I don't even own a bike at the moment, and haven't for a number of years. Never been on the track on a bike, though I did drive race cars some years ago (just time trials, which I won several times). So I do have some experience of the track and traveling at speed, and am not a total ignoramus when it comes to things like vehicle dynamics. I'm an avid race fan... F1 first, followed by MotoGP, WRC and ALMS... I'm NOT a NASCAR guy.

Real men turn right, too.

Besides being a race fan, I'm also very interested in the physics of it all.

Which brings me to this discussion, which will hopefully prove enlightening to both me and to those with more experience.

I'm interested in how racers move their bodies relative to the bike. As a newb, when watching bike racing this is the most striking thing.... how the racers slide their butts off the machine and drop a knee to literally contact the pavement.

I think I understand the physics of this. It gets your CG lower and lets you pull more lateral G before the tires give up.

However, the details of how it works on a practical level interest me and I want to check what I think I'm seeing against the knowledge of those who have actually been there and done that.

Right now I'm watching the 250 MotoGP race in France and I see the riders getting their bodies well off-center from the bikes when cornering, but it's NOT just moving the butt.

The most obvious thing to the casual observer is the knee drag and the butt hanging off the bike, but I'm seeing something beyond that, and I think it's much more important... the movement of the head relative to the centerline of the bike. The head, and indeed the entire upper torso, moves MUCH more than the butt.

A typical turn shows me the head moving something like 8 to 10 inches off center (right edge of the windscreen adjacent to the left edge of the helmet visor) while the butt is only about half a cheek off center (maybe 5 inches?).

I further observe that the riders seem to be leading with their inside shoulder, kind of like a slalom ski racer.

Looking at videos of ordinary riders on YouTube, what I often see is them getting this backwards...they hang their butts, but keep their upper bodies over the bike centerline, as if they're trying to emulate the pose without understanding why you need to hang off the bike in the first place.

I speculate that it has to do with mass. In a former life I was a whitewater kayaker, and I learned how massive your head is...to roll a kayak upright you need to snap your head downwards because it weighs about as much as a bowling ball.

So... extending this idea, it makes a lot of sense to me that the whole butt-hang, knee-drag thing is the END of the process, not the beginning, and not the actual goal. It's all about your head, first and foremost. Move your head, shoulders and chest into the turn and the rest should follow.

In other words, when diving into a turn, you move your head and upper chest into the turn (forward and laterally) first , and when you reach the limit of how far you can take that extension, then you move your whole body laterally, hanging your butt off the bike. (Actually it's probably not as sequential as that, but the description does illustrate the process.)

This is just a thought experiment. I'm trying to gauge if my gut instinct is correct.

Am I in the ballpark? I welcome discussion.

From my understanding the motogp bikes have so much grip that simply counter steering will not lean the bike at those speeds, they have to actually muscle the bike down by using their knees on the tank. That being said the knee dragging acts as a contact point so they can reference their lean angle and to keep the most amount of tire contact to increase traction.

Now I have never raced motorcycles before so my knowledge is limited and from no experience other than riding some fast paces in the mountains. Im sure some of the track guys can help you out a bit better.

Thanks, but what I'm really interested in here is the shift of mass... the idea that moving your (heavy) head and (heavy) upper torso relative to the bike's centerline is much more important than merely getting your butt off center.

Since I don't actually know first-hand if this is a valid concept, I seek further discussion on the topic.

Yea the track guru's will probably chime in sooner or later...until then more comments from the peanut gallery:

-You should pick up some of the existing literature on this subject matter. I myself have gone through Nick Ienatsch's Sport Riding Techniques...full of big pictures of riders mid-turn.

-Each pro rider will typically have his or her own variation on the technique. Different strokes for different folks as it were. Some people will drag their knees, other will drag their knees and elbows.

-What is consistent however, is where their eyes are looking and their head position. Any racer worth his/her salt will have his/her head contorted into a position where they're looking through the turn, as far out as possible.

-In terms of the phsyics: http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_dynamics

That oughta keep you busy for a while :D

-What is consistent however, is where their eyes are looking and their head position. Any racer worth his/her salt will have his/her head contorted into a position where they're looking through the turn, as far out as possible.

Except for the greatest motorcycle racer of our time, and perhaps any time. Rossi often just looks down at the inside of the turn rather than looking ahead much at all. When asked about it, he says that he knows where the turn goes. :idunno: It's not like taking riding tips from people at that level apply in any way to mere mortals anyway...

2015 2016
2017

Except for the greatest motorcycle racer of our time, and perhaps any time. Rossi often just looks down at the inside of the turn rather than looking ahead much at all. When asked about it, he says that he knows where the turn goes. :idunno: It's not like taking riding tips from people at that level apply in any way to mere mortals anyway...

2015 2016
2017

Rossi's an anomaly.....getting riding advice from him would be akin to getting weight lifting advice from Schwarzenegger and wondering why you don't end up huge :p

The more weight that is inside the centerline of the bike in a turn, the less lean angle is necessary for that particular speed. Whether that weight is torso, butt, head, or huge brass cojones, weight is weight. :) There are a couple reasons why less lean angle is sought:

- sometimes you truly need more lean angle to keep the hard parts of the motorcycle from actually contacting the pavement.
- if not at absolute max lean, less lean angle allows the suspension to work better. Bike suspension works best when straight up and down; when leaned over much of the duties of the suspension are handled by the tires and frame flex alone.
- at less lean angle, the bike can be brought up out of the lean faster, which allows the rider to accelerate faster as the rear tire gets better grip sooner as it rolls out of the lean

As you've seen, riders have a number of different techniques to get some weight inside of the bike, yet still be comfortable handling the controls of the motorcycle. If they can't properly control the brake and throttle while contorted in a certain position, it's all for nought anyway. Some of the fastest riders on the planet ride in "unconventional" ways, yet still are faster than most of their peers. Troy Bayliss rides crossed-up (which generally means that his shoulders are closer to the center of the bike when he's leaning than his hips). He definitely doesn't lead with his head, and he's still got a couple WSBK championships to his name. Neil Hodgson's the same way.

Rossi's an anomaly.....getting riding advice from him would be akin to getting weight lifting advice from Schwarzenegger and wondering why you don't end up huge :p

Yeah, I wouldn't look at how he rides to mimic....
Reminds me of when I learned to skateboard when I was 10YO. I learned a jacked up version of "goofy foot," which prevented me from gaining much skill... I could never unlearn it, but I sure tried.

Back to bikes... Thankfully I took the MSF class when I had only 500 mi. under my belt. It was soon enough that I was able to unlearn bad habits I was picking up. But if I had many more miles, I suspect they would be harder to unlearn.

I suggest learn the conventional way, and when you have that down, THEN maybe personalize is a bit if it helps you. I'm no expert, but I would say the same thing if we were talking about a golf swing (although LESS of an expert there!).

Agreed. I just wouldn't stress about BP for new riders, or even not-so-new riders. As long as you're not doing anything really goofy (leaning your body opposite the turn; pushing the bike down in turns), it won't keep you from keeping a very quick street pace without even approaching the bike's limits. IMO there are a million other things to work on before worrying about BP, like line selection, appropriate steering inputs, braking, and just general comfort with speed on the bike. At some point if people start to run into limits (clearance problems, traction problems, etc.), then starting to work on BP isn't a half-bad idea. Getting to the track certainly accelerates the process of finding those limits; trying to bump up against them for the first time on the street can occasionally end painfully.

Have you seen this vid on body positioning? :p
http://www.ninjette.org/forums/showthread.php?t=19533

My point... learn to ride the bike first. :D

Worry about maximizing body control over the bike after you've mastered the basics.

the biggest reason that you hang your body off into a turn is to change the bikes center of gravity (as you pointed out). this allows you to carry more corner speed with the bike more upright. the more upright the bike is the more traction you have and the more you can accelerate. sitting upright will only get you so far through a corner before you run out of tire or start dragging pegs, so you gotta hang off when you start reaching that point in order to carry more speed. of course once you get good enough you find yourself hanging off and still out of tire/clearance, and trying to find more ways to get your bike through the turns faster.

theres a lot more going on than that though. among other things, you're also pushing down on the outside peg with your foot to help drive the rear tire into the ground for more traction and some times even driving your inside knee into the pavement in order to pick the bike back up when it starts to slide.

a lot of body position and technique can be learned and observed a lot easier on some smaller bikes since they're so much easier (and safer) to take to their extreme, and the body positions tend to get more exaggerated (or at least look that way). have a look at some of my picts (click the one below) if you wanna see some examples. this pict is a honda xr100 in motard trim... mmmm.... 17" slicks ;)

http://farm2.static.flickr.com/1163/1476993783_4fabb8ce2e.jpg (http://www.flickr.com/photos/jbroom/sets/72157594378204198/)

Thanks Broom. You explained that so a novice such as myself can understand.

Excellent explanation indeed! BP varies from rider to rider and getting it "right" takes some time. I'm no pro, but I've seen some TERRIBLE BP on the track. Over time as you become a better rider and good BP comes naturally, you'll begin to take notice of how poorly some riders position themselves in turns. Granted they make it through the turn, but they do it fighting physics the whole way through.

At the track last year:
http://farm4.static.flickr.com/3226/3023082058_b66dbc623a.jpg
http://farm4.static.flickr.com/3060/3023082130_a15215518b.jpg

Angle from the back setting up for a turn:
http://thebeastisback.com/ninja250/streetsofwillow_41909.jpg

I think this chart is relatively well thought out:

http://www.ninjette.org/forums/picture.php?albumid=10&pictureid=1552

Alex, please enlighten me on something. Several posts back you wrote:

The more weight that is inside the centerline of the bike in a turn, the less lean angle is necessary for that particular speed. Whether that weight is torso, butt, head, or huge brass cojones, weight is weight. :)

I understand the reason why one would get weight off the bike. But in the top-left image in the pic you just posted, it shows the rider with his head way up (head weighs about as much as a bowling ball... considerable mass) and his whole torso shifted over.

They're saying this is what NOT to do, right?

So?.......

Also, check this out:

QCg3BMGe52M

Pic 1 is a completely neutral position. It's not "wrong", but probably not as advantageous as pics 3,4, or 5. Pic 2 demonstrates "wrong".

Pic 1 is a completely neutral position. It's not "wrong", but probably not as advantageous as pics 3,4, or 5. Pic 2 demonstrates "wrong".

You haven't watched much supermoto racing then have you? :D
http://img.photobucket.com/albums/v137/mistabob/YZ-supermoto-extreme-lean.jpg

But yeah your right when it comes to sport bikes.
This style not only offers no advantage on a sport bike I'd imagine,
it would also probably be a bad idea to try it due to them not being able to lean over anywhere near as far as a motard.

that style of riding is best suited for tighter tracks and stuff anyways. most people go back to riding motards like a sportbike on typical sized sportbike tracks.

not sure how riding like that can be fast on pavement at all, but it is... and its pretty fun too :D

;) Motards don't count. But they are a heck of a lot of fun. Though I still never put one as close to the ground as some of those great pics I've seen, including yours right there...

Additional "lean info" from a BMW forum:

www.bmwmoafoundation.org/motosafe/article0811.html

www.bmwmoafoundation.org/motosafe/article0808.html

May I suggest some book study .Kieth code Twist of the wrist volume one and two . since you are interested in the physics of motorcycles . between that and how the mind causes the body to mess up the physics is a very interesting start to learning to ride better.

Agreed. I just wouldn't stress about BP for new riders, or even not-so-new riders. As long as you're not doing anything really goofy (leaning your body opposite the turn; pushing the bike down in turns), it won't keep you from keeping a very quick street pace without even approaching the bike's limits. IMO there are a million other things to work on before worrying about BP, like line selection, appropriate steering inputs, braking, and just general comfort with speed on the bike. At some point if people start to run into limits (clearance problems, traction problems, etc.), then starting to work on BP isn't a half-bad idea. Getting to the track certainly accelerates the process of finding those limits; trying to bump up against them for the first time on the street can occasionally end painfully.

^ I really like that post :)

:yo: