Limit cornering on bikes

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Jolle
Jolle
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Location: Dordrecht

Re: Limit cornering on bikes

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McMrocks wrote:
Wed Mar 18, 2020 9:36 am
Edit: "Countact patch" well spelled

https://www.directupload.net

When cornering you should have four forces acting on the bike: Gravitational force and Centrifugal force. Both act at the centre of gravity (Cg). And the forces acting on the tire (vertical and horizontal).

The gravitational force (Fy) wants to pull the bike down. While the centrifugal force (Fx) wants to straighten the bike up.

When cornering steady, the torques of those forces (rotating around the contact patch of the tire) are equal.

You have two options to stop the cornering(without changing the loads on the tyre):
Increase ly to increase the lever of the centrifugal force(Fx) --> i.e. move your upper body upwards
Decrease ly to decrease the lever of the gravitational force (Fy) ---> reduce your hanging off
Well, if you move your body around of the bike, normally the bike just moves in the opposite direction and for the forces the result is zero.

what does change is the curve of the tires because of the width and profile of the tires, making the corner sharper if you move your body (and lean the bike more) out, and shallower if you move your body in. Normally you only use this technique when you go dead slow. It's the easiest and best wel to make a u-turn, just lean the bike down as flat as you dare.

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Andres125sx
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Joined: Tue Aug 13, 2013 9:15 am
Location: Madrid, Spain

Re: Limit cornering on bikes

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J.A.W. wrote:
Tue Mar 17, 2020 11:37 pm
If you check the 'save' vid, in slo-mo Andres, you can clearly see just where
the rider backs off the throttle, then winds it back on, to straighten up,
(as a needful inertia-control input function).

There are many complicated inter-related dynamics involved in cornering a
one-track vehicle, & any scenario may develop unexpectedly - yet must be
managed accordingly - via skilled responses involving proper inputs,
applied in a timely fashion, if a crash is to be avoided, no?
Sorry to say this JAW, but I was assuming you know how to ride a bike, but you´ve just proved the opposite!

Backing off the throttle is very different to cut-off, when a powerslide goes too far you obviously need to back off the throttle as that´s the cause of the slide, but if you cut-off the throttle completely the crash is guaranteed at 100%, and it will be an ugly crash btw
J.A.W. wrote:
Mon Mar 16, 2020 5:24 am
one being the low 'engine braking' inertia of the 2T machine, when he cuts the throttle to stop
the powerslide
Talking about engine braking inertia of the 2T machine to stop a powerslide you´re proving you have no idea about controlling motorcycles, not even a vague idea! :o .

To control a powerslide wich went too far you have to stop accelerating hard, but you cannot stop accelerating completely, or the wheel will bite the tarmac (I think in english this is how you say it) suddenly and you will crash. It doesn´t matter if big or low engine braking, if while powersliding you go from accelerating phase to decelerating, you´re done, period, no matter how small is the deceleration. Anyone with a bit of experience in motorcycling knows this, what is shocking is realicing you have no idea about controlling a bike at all, but even so you´re so vocal in this and other similar threads #-o

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Andres125sx
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Joined: Tue Aug 13, 2013 9:15 am
Location: Madrid, Spain

Re: Limit cornering on bikes

Post

McMrocks wrote:
Wed Mar 18, 2020 9:36 am
Edit: "Countact patch" well spelled

https://www.directupload.net

When cornering you should have four forces acting on the bike: Gravitational force and Centrifugal force. Both act at the centre of gravity (Cg). And the forces acting on the tire (vertical and horizontal).

The gravitational force (Fy) wants to pull the bike down. While the centrifugal force (Fx) wants to straighten the bike up.

When cornering steady, the torques of those forces (rotating around the contact patch of the tire) are equal.

You have two options to stop the cornering(without changing the loads on the tyre):
Increase ly to increase the lever of the centrifugal force(Fx) --> i.e. move your upper body upwards
Decrease ly to decrease the lever of the gravitational force (Fy) ---> reduce your hanging off
There´s something else to consider. People with no experience in real world usually take it as if wheels goes on rails, until you go beyond the limit and then they slide, but that´s not true.

When you´re close to the limit, wheels are actually sliding a bit... or a lot. If you straighten up the bike for that you need to move your body down so the resultant is equal, but moving the bike up you´re increasing the contact patch of the wheel. This reduces the slide, and with less slide centrifugal force goes up, straightening the bike up by itself.

A good example of this are highside crashes wich are the extreme scenario of this phenomenom, but the same. Only difference is the rear wheel did slide way too much so when grip is recovered centrifugal force goes up too much too sharply, causing the highside


Jolle
Jolle
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Joined: Wed Jan 29, 2014 9:58 pm
Location: Dordrecht

Re: Limit cornering on bikes

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Even in a non-sliding corner, when you close the throttle, the bike will come back up and you'll be heading for an ugly crash on the outside of the corner.

For a powerful Motogp (especially ones with a dirt track background) slide, many riders (before the days of traction control) use the rear brake to control the precise amount of torque going trough the rear tire. This is why some of these former dirt trackers preferred a larger rear brake so they could manage it better. Just look at the (pre-traction control) Honda's of Hayden and Pedrosa.

J.A.W.
J.A.W.
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Re: Limit cornering on bikes

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Andres125sx wrote:
Wed Mar 18, 2020 11:33 am
J.A.W. wrote:
Tue Mar 17, 2020 11:37 pm
If you check the 'save' vid, in slo-mo Andres, you can clearly see just where
the rider backs off the throttle, then winds it back on, to straighten up,
(as a needful inertia-control input function).

There are many complicated inter-related dynamics involved in cornering a
one-track vehicle, & any scenario may develop unexpectedly - yet must be
managed accordingly - via skilled responses involving proper inputs,
applied in a timely fashion, if a crash is to be avoided, no?
Sorry to say this JAW, but I was assuming you know how to ride a bike, but you´ve just proved the opposite!

Backing off the throttle is very different to cut-off, when a powerslide goes too far you obviously need to back off the throttle as that´s the cause of the slide, but if you cut-off the throttle completely the crash is guaranteed at 100%, and it will be an ugly crash btw
J.A.W. wrote:
Mon Mar 16, 2020 5:24 am
one being the low 'engine braking' inertia of the 2T machine, when he cuts the throttle to stop
the powerslide
Talking about engine braking inertia of the 2T machine to stop a powerslide you´re proving you have no idea about controlling motorcycles, not even a vague idea! :o .

To control a powerslide wich went too far you have to stop accelerating hard, but you cannot stop accelerating completely, or the wheel will bite the tarmac (I think in english this is how you say it) suddenly and you will crash. It doesn´t matter if big or low engine braking, if while powersliding you go from accelerating phase to decelerating, you´re done, period, no matter how small is the deceleration. Anyone with a bit of experience in motorcycling knows this, what is shocking is realicing you have no idea about controlling a bike at all, but even so you´re so vocal in this and other similar threads #-o

On the contrary Andres, since if you actually watch the vid, you can see for yourself, what the
rider is doing with the movements of his throttle hand, yet plainly, he does not crash, which
shows he understands the dynamics situation full-well, & furthermore, if you'd had sufficient
hard/fast riding experience with powerful 2T & 4T bikes on a tarmac surface, you'd also have
a more realistic understanding of the engine inertia issue.

4T race bikes had to go to high off-throttle 'idle' engine rpm, then 'slipper' clutches, followed by
a sophisticated electronic control suite - to overcome the 'inertia drive' issue - on a cut throttle..

Back when 500cc 2T bikes were raced, no such electronic assistance was available, & it was
the mark of a championship winning rider that he had fine throttle control coordination skills.
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

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hollus
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Joined: Sun Mar 29, 2009 12:21 am
Location: Copenhagen, Denmark

Re: Limit cornering on bikes

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May I suggest you move it to PM, guys?
¡Puxa Esportin!

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Andres125sx
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Joined: Tue Aug 13, 2013 9:15 am
Location: Madrid, Spain

Re: Limit cornering on bikes

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J.A.W. wrote:
Wed Mar 18, 2020 5:44 pm
if you'd had sufficient hard/fast riding experience with powerful 2T & 4T bikes on a tarmac surface, you'd also have
a more realistic understanding of the engine inertia issue.
I have a perfect understanding of the engine inertia issue, but you´re mixing things wich are not related at all, proving once more you have no idea about motorcycles, but still try to teach those who enjoy way more experience than yourself :wtf: :wtf:

The engine inertia of 4T engines is well known, but as I tried to explain and you ignored, during a powerslide you cannot cut the throttle or you´ll instantly crash, so engine inertia is NOT RELATED with the subject. Engine inertia only applies when throttle is cut-off, a situation wich will never happen during a powerslide, nor during a corner when close to the limit (or you´ll crash again), wich is the question the OP brought up

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Andres125sx
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Joined: Tue Aug 13, 2013 9:15 am
Location: Madrid, Spain

Re: Limit cornering on bikes

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Jolle wrote:
Wed Mar 18, 2020 2:41 pm
Even in a non-sliding corner, when you close the throttle, the bike will come back up and you'll be heading for an ugly crash on the outside of the corner.

For a powerful Motogp (especially ones with a dirt track background) slide, many riders (before the days of traction control) use the rear brake to control the precise amount of torque going trough the rear tire. This is why some of these former dirt trackers preferred a larger rear brake so they could manage it better. Just look at the (pre-traction control) Honda's of Hayden and Pedrosa.
Exactly. Actually in MX that is done also with the front brake, when on a rut obviously :wink: but I did never master that technique, well I never mastered ruts to be sincere :oops:

But the rear brake + throttle technique was very very useful. Can´t explain it but it does provide more grip believe it or not. I think it must be related with the bike height, as using both the throttle and rear brake simultaneously the rear suspension is compressed. That´s my best bet about the phenomenon but I really have no idea about the real explanation

But I can assure it works, I´ve used it a lot. Even on a slippery right hand corner it´s safer using this technique even if you´re forced to keep your leg on the footpeg. That´s how I was conviced about the technique, on a race with a right hand corner with mud, inverted camber and descending a hill. A real hell of a corner I was hating until I dared to try it with throttle and rear brake and... omg what a difference!

Since then I used it a lot. Also tried with the front brake when into a rut but I have always hated ruts and never had the confidence to master that

aral
aral
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Joined: Sat Apr 03, 2010 9:49 pm

Re: Limit cornering on bikes

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As this thread has descended into a personal battle about who is right and who is wrong, it is being locked. If the protagonists want to continue their argument, could they please do so by using the PM facility, as already requested.
Thanks