Stoner VS Rossi, the never ending debate

[TwoStroke Institute]

That's a good find motor and I think encapsulates Rossi's position.

[motomania]

Nice find Motor. Definitely a bit different take on all of it, interesting food for thought for sure.

[freighttrain]

that was a pretty interesting read... thanks motor.

never really heard it explained in such a way, but it sure makes sense.. especially comparing the analysis with the photos.
nice one...

[Cappra]

You may like it but I'm calling misleading B.S. (no disrespect for Rolando, sometimes great riders are the worst person to ask for an explanation - you never question a skill, you question knowledge - skill is demonstrated (a doing thing)).

In fact most discussion about lines and style in the general press is misleading if not entirely journalistic posturing and pontificating for profit. There is no magical mythical line or style to make a rider fast, it is the way he thinks his way through the corner. It is how the rider adapts to each corner each lap with subtly varying inputs. If he is adapting he is learning; learning is change, change is learning - no change no learning.

Read, or re-read , this; http://motomatters.com/interview/2012/0 ... a_mot.html and the comments. All the commentary miss the most important insight offered by Casey. Casey is describing how he is thinking and adapting his way through a corner "........but to slide and be fastest is something more complex...", "One of the reasons explaining how he slid the rear was so difficult is because there was not a single method to achieve it, and each corner required a different approach, Stoner explained. "It's more or less impossible [to give one answer], because every situation is different, every corner you must slide through is different to the others," Stoner said. " etc.

If you want insight look here; http://en.wikipedia.org/wiki/Four_stages_of_competence If you really want to get your head in a mess get your head around the fifth stage; "Some refer to reflective ability, or "conscious competence of unconscious competence", as being the fifth stage, while others use the fifth stage to indicate complacency."

I don't want to get too much into a detailed argument with Rolando's theory but it doesn't hold water for me. He says that Stoner can increase both his speed through the corner and hold a tighter line which means Stoner has significantly increased the centrifugal force acting on the bike (compared to Rossi) by increasing the value of two of the forces influencing centrifugal force. That increase is an exponential increase in the centrifugal force. To offset this increased centrifugal force Rolando says that Stoner is using increased surface area (by leaning further off the bike) and increased aerodynamic drag. Although aerodynamic drag is exponential I doubt that the value of that one force will increase proportional to the other two combined forces (speed and radius).

I also doubt that there is any significant difference in the amount of drag created by Stoner and Rossi. From the photo shown it is the positioning of the weight (Stoner low and forward) that is probably more significant. To fully develop the aerodynamic drag argument you would also have to calculate the riders drag using height and width of shoulders etc. I would guess that Rossi's increased surface area, given his height advantage, would offset any increased drag created by the smaller Stoner leaning off fractionally more.

I think referring to parachutes and Spinnakers is colourful but misleading.

The two photos offered are no evidence at all. They are taken at different angles at different stages of the corner. And they are static. The different lines could be the result of different stages of the corner and different choices as much as different styles or different bikes.

[Oscar]

Welcome to the mad mob, Cappra, and a great post!

He says that Stoner can increase both his speed through the corner and hold a tighter line which means Stoner has significantly increased the centrifugal force acting on the bike (compared to Rossi) by increasing the value of two of the forces influencing centrifugal force.

That statement (Ronaldo's, not yours) is actually wrong according to the laws of physics. Centrifugal force

depends on the mass of the object, the speed of rotation, and the distance from the center. The more massive the object, the greater the force; the greater the speed of the object, the greater the force; and the greater the distance from the center, the greater the force.

( http://phun.physics.virginia.edu/topics/centrifugal.html )

If Stoner is in fact placing his body further to the inside of the corner, then the c/g of the assembly (bike+rider) is at a lesser radius than it would be if his body was more centralised and thus the centrifugal force is lesser - not greater. The mass of the assembly remains constant as does the arc, so by reducing the effective radius Stoner can in fact increase the velocity (speed of rotation) of the assembly for the SAME centrifugal force, which has to be resisted by the tyres.

I think referring to parachutes and Spinnakers is colourful but misleading.

Absolutely right. The aerodynamics involved is far more complex than just the position of the body. There is a fair argument to suggest that a lower and more inwards position of the rider's body actually allows the outwards-acting force of lift from the fairing to increase, since there is less of an interruption to the airflow on the outwards side of the fairing. The air acting on the outside of the fairing is already traveling faster than that on the inside (because it is describing a larger arc). By positioning the rider's body further away from the outside, the rider cleans up the airflow on the outside fairing thus allowing more lift to be generated. That may or may not be adequately compensated for by the added drag of an asymmetrical frontal area relative to the contact patch but there is a definite swings and roundabouts between the two effects and you can't simply look at the rider body position in isolation of the sum of all effects on the assembly. It is interesting to note in this respect that Ducati pretty rapidly abandoned the winglets, which cleaned up the airflow over the fairing as a by-product of adding to the cooling airflow but due to the added lift on the outside of the fairing were considered to have added to the understeer problem! ( I have my doubts that they really did make much difference, I think the understeer was endemic anyway - it certainly appears to be).

[sir_nj]

Cappra, as I understand it you are saying that Casey loads the front more by shifting his weight forward and this has sod all influence on the aerodynamics? If so then I would have to fully support that.

Oscar and Cappra, I'm not sure why body position would have much of an influence on the overall centrifugal force of combined bike and rider since isn't the radius of their combined turn many many metres not cm which is all any rider is able to vary their body position by? Or have I missed the point (wouldn't surprise me ) and you are actually discussing lean angles?

[Rusty Bucket USA]

Interesting related read:

http://www.gpone.com/index.php/en/20120 ... otoGP.html

It will take me a while to digest Cappra's and Oscar's comments, but FWIW, I think they're right. The more I think about this opinion, the more I think it is only 50% true, at best.

[Oscar]

Cappra, as I understand it you are saying that Casey loads the front more by shifting his weight forward and this has sod all influence on the aerodynamics? If so then I would have to fully support that.

Oscar and Cappra, I'm not sure why body position would have much of an influence on the overall centrifugal force of combined bike and rider since isn't the radius of their combined turn many many metres not cm which is all any rider is able to vary their body position by? Or have I missed the point (wouldn't surprise me ) and you are actually discussing lean angles?

I agree completely, what I was on about is the fact that Ronaldo has got his physics a bit muddled (or the translation doesn't do his thesis justice, which is possible). I think body weight positioning has far more effect and with regard to Stoner, Lucy's observation several years ago still sticks in my mind as the definitive one for Stoner: 'moves around like a hyper-active gibbon'. A revisit of Qatar and Stoner's lines and body position later in the race merits study vs. say, Aragon '11. Aerodynamics is very complex and doesn't lend itself to intuitive superficial examination as all - what 'looks' right often isn't.

[RatsMC]

ON another forum someone posted that article and my response was that I just couldn't but it and that the author seemed to be proposing a lot of concepts that just weren't scientifically or factually sound.

However, he got that article linked on just about every MotoGP forum in the world so I guess he accomplished his goal.

[Hanuman]

Cappra, as I understand it you are saying that Casey loads the front more by shifting his weight forward and this has sod all influence on the aerodynamics? If so then I would have to fully support that.

I agree completely, what I was on about is the fact that Ronaldo has got his physics a bit muddled (or the translation doesn't do his thesis justice, which is possible). I think body weight positioning has far more effect and with regard to Stoner, Lucy's observation several years ago still sticks in my mind as the definitive one for Stoner: 'moves around like a hyper-active gibbon'. A revisit of Qatar and Stoner's lines and body position later in the race merits study vs. say, Aragon '11. Aerodynamics is very complex and doesn't lend itself to intuitive superficial examination as all - what 'looks' right often isn't.

The only way the spinnaker analogy makes any sense is not in relation to the centrifugal force <surely centripetal?> around the centre of rotation of the curve, but in creating yaw on the bike-rider combination itself. Hanging off the side might cause a drag-induced moment in the direction that the rider is hanging-off...But like you, I can't see this as consistent or of greater effect than optimising weight distribution by hanging off like a lesser ape.

[Cappra]

In the twilight of his career and in the shadow of the raising talent around him , it is easy to forget the impact that Rossi has had. I thought the following is a good summary. (It is my brother's comments in a series of family emails (the family that rides together stay together ).

"Rossi's universal appeal obviously stems from his results as well as his personality - but a strong part of the appeal is also his "charm" success. His luck on so many occasions was incredible, as I'm sure we all recall - there is something about this persona that converts mere spectators to be fans. I'm certainly one and it feels great to be at a race where his fans radiate a palpable emotion that you can literally feel.

I'll never forget Assen where Rossi slid out on the first lap, restarted and joined last - for every lap after that (the whole race) every spectator in every stand along the straight stood up in a Mexican Wave like motion and cheered as he went past - that's what I mean by palpable................ "

You wouldn't want to rag out, bag out or forget such a rider.

[frankrizzo]

In fact most discussion about lines and style in the general press is misleading if not entirely journalistic posturing and pontificating for profit. There is no magical mythical line or style to make a rider fast, it is the way he thinks his way through the corner.

hi there cappra, you hit the nail on the head with this^^

[TwoStroke Institute]

On about the second paragraph of Keith Code's book "A Twist of the Wrist" it says after entering a corner you only have 1 obligation...... to open the throttle. Also as a good A grade National level rider explained about spinning the rear was , when in the rpm range the rear starts to spin. If you spin at 12,000 and you have to 16,000 until the power drops off you won't spin the tyre much, if you start to spin at 14,500 then you quickly go through to 16,000 without the fear of a massive highside.
I disagree with 'thinking' through a corner a truely great rider 'feels' you do not have the time or attention to think, you control actions should be subconcious, the corner you in you planned for the previous turn, the thinking goes on how you pass other bikes and drop lap times. As Keith Code explains you only have $1 worth of attention to spend at any 1 time, the less you spend on control actions the more attention you have to spend on searching out grip and faster lines, or to plan that last lap pass.

[frankrizzo]

I agree with you, although what you feel governs what you think. And you need to do a lot of thinking off the bike to check your plans and ideas so you can match them up with how it will feel, so i guess we're saying the same thing. I reckon a lot of someones style is the manifestation of stuff that is mostly subconscious.

[JanBros]

Oscar and Cappra, I'm not sure why body position would have much of an influence on the overall centrifugal force of combined bike and rider since isn't the radius of their combined turn many many metres not cm which is all any rider is able to vary their body position by? Or have I missed the point (wouldn't surprise me ) and you are actually discussing lean angles?

if let's say Stoner's body CoG is 10cm lower than Rossi's CoG due to the fact he is hanging more/lower on the bike, the combined CoG rider/bike in Stoner's case will be ca couple of cm's lower than Rossi's.
from the radius point of vieuw that might not matter. but the distance from where the tires touch the ground to the height of the combined CoG is the "torgue arm" at which the centrifugal forces work that want to straighten the bike. The lower you can get the CoG, the lower the force that want's to straighten the bike up will be.

[RatsMC]

I don't think that's true. Centrifugal is an outward pushing force and not a torque force. Overall mass is all that matters, positions of it means nothing when calculating centrifugal force.

I think that where it becomes confusing is that the centrifugal increases as the radius becomes smaller but that is a factor of the change of direction happening faster, not the radius itself.

Of course, I am a garage mechanic not a physicist so I may be wrong.

[JanBros]

I don't think that's true. Centrifugal is an outward pushing force and not a torque force. Overall mass is all that matters, positions of it means nothing when calculating centrifugal force.

I think that where it becomes confusing is that the centrifugal increases as the radius becomes smaller but that is a factor of the change of direction happening faster, not the radius itself.

Of course, I am a garage mechanic not a physicist so I may be wrong.

neither am I

it may be down to my English of course that you don't understand what I mean
What I'm trying to say is : the tires stick to the track, and the centrifugal force is working on the CoG. the CoG can be pushed to the outside in 2 way's :
- the tires loose grip and the bike slides to the outside
-the tires keep their grip and the bike moves to a more upright postion.

in the second case, there is a torgue arm : the vertical from where the tires grip to the CoG. The bigger the arm , the greater the force that will straighten the bike up. by lowering the combined CoG, the arm is shortenned and as a result of that : the force will be lower. After all, that is the reason why we hang on our bikes in corners.

So if Stoner hangs more outside/lower on his bike than Rossi, his combined CoG will be lower and therefore, he can go faster through the corner because he will still have the same force on his tires as Rossi (and as long as the tires grip).


there is a maximum speed for a corner at which a given bike will not flip and tires will grip.
at that point, there is a moment M working on the bike.

M 's formula is M=F x D where F = the force working in the CoG and D is the distance from contacht patch to the CoD.

since M is fix at that perticular moment, if you lower D (by hangin more/lower on the bike) F can be raised by going faster.

[Oscar]

So if Stoner hangs more outside/lower on his bike than Rossi, his combined CoG will be lower and therefore, he can go faster through the corner because he will still have the same force on his tires as Rossi (and as long as the tires grip).

Nope, that isn't quite right.

The line of force resisting centrifugal force must pass through the CoG to the median of the contact patch for the assembly to be in a balanced situation - it doesn't matter how FAR above the contact patch it is. Even if the bike was two metres high, the lean angle for a given speed/radius situation would be the same; any less lean and it tips outwards, any greater and it falls inwards. However, if Stoner gets his effective body mass further inwards, then he moves the total CoG of the assembly inwards and the bike itself can be at effectively a slightly less angle of lean, putting him on a slightly fatter contact patch than the edge of the tyre and providing more area for grip i.e. reaction of the centrifugal force. For the same arc, Stoner can travel slightly faster at the same angle of lean of the bike because the whole assembly is effectively at a slightly greater effective lean angle. It's worth looking at this: http://www.tonyfoale.com/Articles/Balance/BALANCE.htm

However, even that is complicated by the way Stoner tends to slide the bike, which puts the CoG travelling around a slightly larger arc and also provides more reactive force due to the inwards-facing thrust from the rear tyre - it gets hairy about here and Tony Foale's article on tyre force is the best expression I know of it: http://www.tonyfoale.com/Articles/Tyres/TYRES.htm

[lebowski]

"it gets hairy about here and Tony Foale's article on tyre force is the best expression I know of it:"

!!!!!!!

Oscar, it got hairy for me a loooooong way back. ( that's not meant to sound rude by the way)

Interesting discussion but beyond me I'm afraid!

[Cappra]

My comments are limited to debunking Rolando's theory trying to explain the difference in riding performance by attributing to a difference in riding 'style'.

If you disagree with me and think ........

On about the second paragraph of Keith Code's book "A Twist of the Wrist" it says after entering a corner you only have 1 obligation...... to open the throttle.

.......explains the difference in riding performance then we'll just have to disagree. I think both riders understand and meet the "obligation" of getting the throttle open early and hard coming off a corner.

And yet there is still a difference in riding performance between the two. Everything else being the same, I guess that means Stoner must be doing something over and above Rossi, or he's doing the same things better or to a higher degree of excellence.

I disagree with 'thinking' through a corner a truely great rider 'feels' you do not have the time or attention to think, you control actions should be subconcious, ........

I think if you read the prescribed text homework regarding the Stages of Learning you'll realise we are talking about the same thing. We learn both mental and physical skills, and both can be consciously competent and develop into unconsciously competent (and there are degrees and shades in between).

When I say that Casey is 'thinking' his way through the corner I'm saying he in unconsciously competently receiving mental and physical input/data, processing that data into unconsciously competent physical skills. And I think the difference is measured in poofteenths and it is the combination of mental and physical skill advantage.

As Keith Code explains you only have $1 worth of attention to spend at any 1 time, the less you spend on control actions the more attention you have to spend on searching out grip and faster lines, or to plan that last lap pass.

Code is talking about unconsciously competent mental skills - the same thing.

[TwoStroke Institute]

Keith talks about how to ride a bike fast aroud a track.With a forward by Wayne Rainey saying this fellow knows what he's talking about is a good place to start.
The obligation to get on the throttle is nothing to do with coming hard off a corner, it is that when your on the throttle(or brake) you have control. The earlier you are on the throttle the earlier your in control. The bit in between brake and throttle is where you have no control.

[Rusty Bucket USA]

Keith talks about how to ride a bike fast aroud a track...
The obligation to get on the throttle is nothing to do with coming hard off a corner, it is that when your on the throttle(or brake) you have control. The earlier you are on the throttle the earlier your in control. The bit in between brake and throttle is where you have no control.

That is in the context of establishing weight distribution (and by extension, CoG). Not that it takes away from anything you're saying, his point there is about the differing sizes of front and rear tires, and how load is naturally shifted to the rear when accelerating.

And, speaking of that...

The line of force resisting centrifugal force must pass through the CoG to the median of the contact patch for the assembly to be in a balanced situation - it doesn't matter how FAR above the contact patch it is. Even if the bike was two metres high, the lean angle for a given speed/radius situation would be the same; any less lean and it tips outwards, any greater and it falls inwards...

Except that, at the speeds we're talking about, they're not really "balanced". There's considerable slip/drift/slide in nearly every corner, so all the body positioning (and power sliding) is essentially "wedging" the bike against the "balance" lean angle to coax it into going faster. That doesn't take away from your point, either, but I think it's an important detail in realizing why they do what they do.

However, if Stoner gets his effective body mass further inwards, then he moves the total CoG of the assembly inwards and the bike itself can be at effectively a slightly less angle of lean, putting him on a slightly fatter contact patch than the edge of the tyre and providing more area for grip i.e. reaction of the centrifugal force. For the same arc, Stoner can travel slightly faster at the same angle of lean of the bike because the whole assembly is effectively at a slightly greater effective lean angle... However, even that is complicated by the way Stoner tends to slide the bike, which puts the CoG travelling around a slightly larger arc and also provides more reactive force due to the inwards-facing thrust from the rear tyre...

Then, how ironic is it that Stoner appears to be carrying the most lean angle?

The bit about aero drag is true in a general sense, but I believe Rolando has it a little backwards. (Maybe he's been hired for a misinformation campaign! )
The effect of the drag against the rider's body will be applied to the rear wheel (to the extent he's still connected to the bike), which will encourage the bike to "fall" in further. As I keep saying in the "dangling leg" threads, and astutely repeated by Hanuman, there would be a yaw moment when the bike is vertical, but after that, any increased "spinnaker" behavior from the rider would act to increase drag on the rear wheel and shorten its radius around the curve (which the rider would have to mitigate, unless it is a decreasing-radius corner). Any effect on the front wheel would come from direct input by the rider, not aero drag.

Cappra is right: two arbitrarily selected photos do not tell a full story. What kind of lap were each of them on? What was going on in that corner of that lap? More than likely, Rossi was experimenting; at least, in his situation, that's what he should be doing. No one is making the same case about Hayden changing his style, and he'd been on the bike 2 years longer than Rossi.

[ieism]

Can we get back to bickering about who is the better rider now, there is no need for meaningfull discussion here.....

[phil]

Interesting discussion but beyond me I'm afraid!

Me too! lets go for a beer!

Can we get back to bickering about who is the better rider now, there is no need for meaningfull discussion here.....

Neit normal. Neit normal!!

[JanBros]

So if Stoner hangs more outside/lower on his bike than Rossi, his combined CoG will be lower and therefore, he can go faster through the corner because he will still have the same force on his tires as Rossi (and as long as the tires grip).

Nope, that isn't quite right.

The line of force resisting centrifugal force must pass through the CoG to the median of the contact patch for the assembly to be in a balanced situation - it doesn't matter how FAR above the contact patch it is. Even if the bike was two metres high, the lean angle for a given speed/radius situation would be the same; any less .......................

I thinck you are wrong Oscar

have a look at picture nr 3 in your Foale-link

in the picture, the rider sits straight on the bike and so the CoG is in the middle of the bike and the force goes trough the centre of the bike (well, almost because off the tire contact patch). presented by the red lines in my drawing.

now if the biker starts to hang out his body, but keeps the bike at the same angle (because of the increased speed) AND keeps the distance of the CoG to the contact patch the same, you have the blue lines in my drawing.



so yes, the total force that goes through the CoG to the contact patch is exactly the same, but the size of the forces that determine it change ! the centrigugal needs to be bigger . this is correct in my example (just as I said what happens when Stoner brings the combined CoG lower) : he needs to go faster through the corner or he can't keep the bike at the same angle. Let's say Rossi is red and at the bikes maximum angle. Stoner is riding the same, but the next lap, he lowers the combined CoG. He must go faster through the corner to keep the maxumum lean angle ! after all, you can't argue with math :

M1=M2

therefore F1xD1=F2xD2 So if D1 is lowered to D2 because of the movement of the CoG closer to the ground, F2 must raise to keep the bike at the same angle

you are correct that for a specific given speed/radius situation, it doesn't mather where the CoG is on that line, it can be 20m high. but the consequences of it being 20m high and not 1m are : the centrifugal force needs to be a lot bigger (F) , because the distance of it to the CoG is a lot more (D).
after all M1m is a lot less than M20m