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Why Do Motorcyclists Drag Their Knee?


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#1 razorBlades

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Posted 08 February 2011 - 08:43 PM

Why Do Motorcyclists Drag Their Knee?


When watching motorcycle racing on TV you may have  noticed the riders dragging their knees on the racetrack whilst  cornering. The reasons for this are fairly complex and are explained in  this article.    Motorcycle racers drag their knee for a number of different reasons the  combined effect of which results in considerably faster cornering speeds  by increasing the natural limits of the motorcycle and tyres. From the  beginning of motorcycle racing in the early 1900's through to around  1970 every rider raced with their knees tucked in firmly to either side  of the petrol tank. In the early 70's Jarno Saarinen - previously a  motorcycle ice racer - moved into the world of Motorcycle Grand Prix and  brought with him an innovative style of racing which became know as the  "hang-off" style. Through the early 1970's several of the best racers  of the era including Kenny Roberts, Barry Sheene and Paul Smart  developed this riding style - in the highest level of motorcycle racing -  which has became common-place today.

This riding technique makes use of 3/4 inch thick blocks of plastic or  leather - known as knee sliders - which are connected by Velcro to the  upper shin area of the motorcyclist's leathers. Although all sports bike  leathers are equipped with the Velcro which can have knee sliders  attached, it is advised not to use this technique on a public road as it  would be constitute a serious driving offence.

The main reason motorcycle racers drag their knees whilst cornering is  to achieve a greater cornering speed; this is achieved due to the  following factors.

Shifting the Centre of Gravity
To achieve the correct seating position the motorcycle rider slides  their body off the seat in the direction of the inside of the corner by  hooking the underside of their other knee on the edge of the seat. This  riding position shifts the combined centre of gravity of the motorbike  and rider in the direction of the inside of the corner, enabling an  increased cornering speed compared with the speed which could be  achieved with the same angle of lean with the rider sitting upright.

More Speed for No Extra Lean
Another of the factors which results in increased cornering speed is due  to there being a limit of just how low the motorcycle can lean due to  the limitations of grip of the motorcycle tyre, and as there is a direct  correlation between corner speed and the lean angle this ensures a  limit with regard to the cornering speed. Whilst riding through the  corner with a knee in contact with the racetrack, the motorcycle rider  can accelerate gently while supporting some of the weight of the  motorcycle preventing the angle of lean from exceeding the tyres limit.  This results in even greater cornering speed and increased in-corner  acceleration and exit speeds. This technique is used mainly on longer  sweeping corners where the knee is in contact with the tarmac for a  fairly long length of time.

Motorcycle Enthusiasts
The reason above applies to riders of a high level in competitive  motorcycle racing. Other motorcyclists of a lower level may have other  reasons for using the knee-down cornering technique during track day  events - when the race track is available for members of the public to  ride on. Some motorcyclists drag their knee to gauge the angle of lean  to make sure that they are cornering within their abilities or within  the limits of the Motorcycle Tyres and the bike itself.

By using the "hang-off" seating position the perception of speed is  increased as the rider's viewpoint is significantly closer to the  surface of the racetrack. This together with the fact that riding  through a corner with the bike leant over (somewhere near its limits)  with the knee-slider in contact with the tarmac is an exhilarating  experience.

Taking It to Extremes
Some highly talented Moto GP (Modern day Motorcycle Grand Prix) riders  such as Ruben Xaus and Randy de Puniet have taken dragging their knee  one step further by also dragging their elbow at the same time. There is  little evidence that this results in an increase in cornering speed  although it indubitably thrills the crowd.

So for high level motorcycle racers the advantages of this technique are  an in increase in cornering and corner exit speeds; whilst motorcycle  riders on track-days gain less of an advantage in increased speed but do  achieve a more enjoyable and thrilling track-day experience.


source:: Why Do Motorcyclists Drag Their Knee?

Edited by razorBlades, 17 February 2011 - 12:26 AM.

The only time you'll see me down on one knee, is on my bike!

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#2 Ricci

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Posted 08 February 2011 - 10:49 PM

Real question that we should ask :
Why do manufacturers drag their feet (when it comes to supplying a an eager market with moderate-fast medium capacity bikes that don't cost an arm and a leg ) ?

Now have reached an age where parents chant that mantra about settling down , it looks like the future is ;)

Ok I'm done sobbing here, :cheer2:

The theory is known, any idea if there are solid numbers ? Like how much of a speed difference it makes for same bike-rider-track-tyre ?

Now to ask : why does Rossi stick his leg out (foot well off the peg)whilst braking prior to corner entry ? :cheer2:

#3 motionfreak

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Posted 08 February 2011 - 10:53 PM

good info razor !! thanks

Just wanted to add that this technique is very useful in day to day riding on Indian Roads(? :cheer2: ). When approching a corner with not so high speed, say 70-80Kmph, and there is no need to lean a lot, one can just put the knee away from tank and the air drag as well as the bit of shift of gravity created by the leg give much better control. Don't shift your weight, just use the knee.

hope I'm right

#4 satyenpoojary

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Posted 09 February 2011 - 12:12 AM

^thats what weight sensitive beffy riders do too :cheer2:
Not sure if its right thing to do or not!

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#5 pulsurge

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Posted 09 February 2011 - 11:26 AM

Lovely post there RB! But I hate the auto-journos dragging their knees on our punny bikes....don't I know its just for show off :cheer2:
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#6 ch.madhur

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Posted 09 February 2011 - 05:42 PM

Ricci said:


Now to ask : why does Rossi stick his leg out (foot well off the peg)whilst braking prior to corner entry ? ;)


Same Ques is running in my hand while reading the article



Quote

From the  beginning of motorcycle racing in the early 1900's through to around  1970 every rider raced with their knees tucked in firmly to either side  of the petrol tank. In the early 70's Jarno Saarinen - previously a  motorcycle ice racer - moved into the world of Motorcycle Grand Prix and  brought with him an innovative style of racing which became know as the  "hang-off" style. Through the early 1970's several of the best racers  of the era including Kenny Roberts, Barry Sheene and Paul Smart  developed this riding style - in the highest level of motorcycle racing -  which has became common-place today.


Wow, Jarno Saarinen.....hats off to you:hail:



Quote

Taking It to Extremes
Some highly talented Moto GP (Modern day Motorcycle Grand Prix) riders  such as Ruben Xaus and Randy de Puniet have taken dragging their knee  one step further by also dragging their elbow at the same time. There is  little evidence that this results in an increase in cornering speed  although it indubitably thrills the crowd.

Never seen (or Notice actually)
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#7 razorBlades

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Posted 09 February 2011 - 06:55 PM

Ricci said:

The theory is known, any idea if there are solid numbers ? Like how much of a speed difference it makes for same bike-rider-track-tyre ?

It makes a huge difference.. when the bike is leaned more you cannot throttle up.. but when you hang off the bike, the bike does not lean much when compared to the previous and you can throttle up in the mid corner, while the CG remains the sane!

Ricci said:

Now to ask : why does Rossi stick his leg out (foot well off the peg)whilst braking prior to corner entry ? ;)

As far as I have read around, its nothing to do with cornering.. its all about covering the area which cant be used by the attacker to overtake! :P

P.S: Everyone has their own theory. Only the doctor can answer!

pulsurge said:

Lovely post there RB! But I hate the auto-journos dragging their knees on our punny bikes....don't I know its just for show off :D

lol.. but like i said before, maybe to keep the bike as straight as possible in a corner to throttle up before the exit or he has some really bad tyres :P

motionfreak said:

good info razor !! thanks

Just wanted to add that this technique is very useful in day to day riding on Indian Roads(? :P ). When approching a corner with not so high speed, say 70-80Kmph, and there is no need to lean a lot, one can just put the knee away from tank and the air drag as well as the bit of shift of gravity created by the leg give much better control. Don't shift your weight, just use the knee.

hope I'm right

thanks man. Its all about your comfort zone. I have seen people in our group who (i envied) can corner like crazy with their legs tucked in.


ch.madhur said:

Never seen (or Notice actually)

here you go :)

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Edited by razorBlades, 09 February 2011 - 06:58 PM.

The only time you'll see me down on one knee, is on my bike!

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#8 ch.madhur

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Posted 09 February 2011 - 09:11 PM

razorBlades said:

here you go ;)

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ohh man:eek:, how much down they are in those corners, really exciting.

After knee, then elbow, looks like they will start touching there shoulders also:rolleyes:.
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#9 sheelpriye

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Posted 09 February 2011 - 11:37 PM

Thanks for putting up My Spies pic.

Here I go about posting the pic of a rider who is 'unmatched' as far as lean angles go.

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#10 sheelpriye

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Posted 10 February 2011 - 11:45 AM

Thanks for Spie's pic Gopi ;)

Putting the pic of one whose cornering I am fan of and always in awe of his lean angles. He corners his a$$ off :P

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#11 razorBlades

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Posted 11 February 2011 - 12:39 PM

sheelpriye said:

Thanks for Spie's pic Gopi :)

Putting the pic of one whose cornering I am fan of and always in awe of his lean angles. He corners his a$$ off :D

i am a fan of spies aswell.. no wonder why they call him "THE ELBOWZ" :D

i loved his interview, the one between the two texans, he saying every track is in the shape of an animal :P

and check this out

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Edited by razorBlades, 11 February 2011 - 12:46 PM.

The only time you'll see me down on one knee, is on my bike!

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#12 satyenpoojary

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Posted 11 February 2011 - 01:14 PM

Who is that on the super moto bike!

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#13 razorBlades

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Posted 11 February 2011 - 02:24 PM

satyenpoojary said:

Who is that on the super moto bike!

no idea man.. found the pic in google and tried to find him but :P
The only time you'll see me down on one knee, is on my bike!

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#14 DineshSamtani

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Posted 11 February 2011 - 05:29 PM

Super Article bro....now lets see all this in action, some live demos plz Gopi....

Ricci said:

Real question that we should ask :
Now to ask : why does Rossi stick his leg out (foot well off the peg)whilst braking prior to corner entry ? :P

I think it is to cover the attack space and on some lines to distract the opponent if he is not used to seeing the leg stuck out  :):p
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#15 nin

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Posted 14 February 2011 - 02:31 AM

[/QUOTE]

holy mm....:frusty:




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