Limit cornering on bikes

[Erunanethiel]

Anyone that rides a bike knows you have to push is to stay in a corner. There is no curve where it’s balanced. If you straighten the steering, the bike will erect itself again, due to the gyroscopic effect of the wheels. With clever frame geometry this push is very light, but you keep a pressure on the inside clip-on the whole way trough a long corner.

There is so much more to motorbike dynamics then a centrifugal force and gravity. Rear tyre width, cords, engine configuration, frame flex, on/off throttle etc etc all play a big part. That’s why you need more then one bike...

I don´t think thats right. A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.

Thats why carbon wheels and counter rotating cranks are so good, they make the bike easier to flick from side to side.

In a steady state limit cornering cornering situation, a bike shouldn't be able to stand back up because it has to countersteer into the turn, momentarily carving a tighter line than before. But if it is at the edge of traction, it can't.

but maybe when you do the opposite of counter steering to stand the bike up you increase the front contact patch but also increase the diameter of the front wheel causing you to turn less?

Increase the wheel's diameter?

[Andres125sx]

Anyone that rides a bike knows you have to push is to stay in a corner. There is no curve where it’s balanced. If you straighten the steering, the bike will erect itself again, due to the gyroscopic effect of the wheels. With clever frame geometry this push is very light, but you keep a pressure on the inside clip-on the whole way trough a long corner.

There is so much more to motorbike dynamics then a centrifugal force and gravity. Rear tyre width, cords, engine configuration, frame flex, on/off throttle etc etc all play a big part. That’s why you need more then one bike...

I don´t think thats right. A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.

Yes, that is exactly what gyroscopic effect means, the wheels try to keep straight up by theirselves, if you lean the bike you need to keep some force (your weight outside the contact patch to cause a turn/momentum wich counteract the gyroscopic effect) to keep the bike leaned.



Once you reduce your conteracting force moving your body closer to the contact patch, you´re reducing the turn/momentum and breaking the balance, so the bike start to straight up by itself


The effect is extremelly noticeable, I come from MX where the effect does not exist or is not noticeable because of the reduced speed, and first time I leaned a street bike on a fast corner I got really scared when the bike didn´t want to be leaned and I almost went off road


I think the problem with the OP is he´s taking a rider-bike on a corner as a natural balance, and it is, but he´s missing a rider can apply new forces wich will break the balance at will, just a gesture to lean the bike a bit more or less is breaking the balance

[Phil]

( ) Nevermind, wrong topic.

[Erunanethiel]

Anyone that rides a bike knows you have to push is to stay in a corner. There is no curve where it’s balanced. If you straighten the steering, the bike will erect itself again, due to the gyroscopic effect of the wheels. With clever frame geometry this push is very light, but you keep a pressure on the inside clip-on the whole way trough a long corner.

There is so much more to motorbike dynamics then a centrifugal force and gravity. Rear tyre width, cords, engine configuration, frame flex, on/off throttle etc etc all play a big part. That’s why you need more then one bike...

I don´t think thats right. A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.

Yes, that is exactly what gyroscopic effect means, the wheels try to keep straight up by theirselves, if you lean the bike you need to keep some force (your weight outside the contact patch to cause a turn/momentum wich counteract the gyroscopic effect) to keep the bike leaned.

https://www.youtube.com/watch?v=8H98BgRzpOM

Once you reduce your conteracting force moving your body closer to the contact patch, you´re reducing the turn/momentum and breaking the balance, so the bike start to straight up by itself


The effect is extremelly noticeable, I come from MX where the effect does not exist or is not noticeable because of the reduced speed, and first time I leaned a street bike on a fast corner I got really scared when the bike didn´t want to be leaned and I almost went off road


I think the problem with the OP is he´s taking a rider-bike on a corner as a natural balance, and it is, but he´s missing a rider can apply new forces wich will break the balance at will, just a gesture to lean the bike a bit more or less is breaking the balance

Any move you do that has a result of bringing the system's center of mass up or out will either increase the centripetal force requirement from the tire just to hold on (which it can't) or decrease normal force on the tire (which will make you crash)

[Jolle]

I don´t think thats right. A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.

Yes, that is exactly what gyroscopic effect means, the wheels try to keep straight up by theirselves, if you lean the bike you need to keep some force (your weight outside the contact patch to cause a turn/momentum wich counteract the gyroscopic effect) to keep the bike leaned.

https://www.youtube.com/watch?v=8H98BgRzpOM

Once you reduce your conteracting force moving your body closer to the contact patch, you´re reducing the turn/momentum and breaking the balance, so the bike start to straight up by itself


The effect is extremelly noticeable, I come from MX where the effect does not exist or is not noticeable because of the reduced speed, and first time I leaned a street bike on a fast corner I got really scared when the bike didn´t want to be leaned and I almost went off road


I think the problem with the OP is he´s taking a rider-bike on a corner as a natural balance, and it is, but he´s missing a rider can apply new forces wich will break the balance at will, just a gesture to lean the bike a bit more or less is breaking the balance

Any move you do that has a result of bringing the system's center of mass up or out will either increase the centripetal force requirement from the tire just to hold on (which it can't) or decrease normal force on the tire (which will make you crash)

You are reasoning from the assumption that you need any kind of force to get a motorcycle from a it's curve while the opposite is the case. You need to apply constant input/force to have it leaned over into a corner. If you take away that force, it will bring itself up and go straight, without any extra stress on the tires. Even with carbon wheels and small engine displacement (or with a longitudinal crankshaft). A backwards rotating crank is not for having less gyroscopic effect by the way, it contribute a very small bit to keep the front on the road when accelerating.

[Andres125sx]

Any move you do that has a result of bringing the system's center of mass up or out will either increase the centripetal force requirement from the tire just to hold on (which it can't) or decrease normal force on the tire (which will make you crash)

I´m probably misunderstanding what you´re trying to say, as what I get is you´re saying any move of the rider can only have two consequences, one wich is not possible, and the second wich is crashing, so I must be missing something because that has no sense to me.


You can change bike lean angle without crashing nor modifying curve radius, rider can lean as much as the bike (old style), more than the bike hanging from it (normal technique currently), or less than the bike (MX while trying to cause an oversteer). You can change your lean angle and bike lean´s angle (inversely) at any corner at any time. It is possible, and you won´t crash. Well at least I don´t, can´t guarantee you won´t tough

[Tommy Cookers]

......A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.
Thats why carbon wheels and counter rotating cranks are so good, they make the bike easier to flick from side to side.

a spinning wheel does automatically 'want to stand up' ....

ie a rotating wheel that is yawing develops a .....
roll moment proportionate to the yaw rate and directionally away from the roll displacement (lean) associated with the yaw

(and a yawing moment proportionate to the roll rate and directionally away from the roll displacement associated with yaw)

[SectorOne]

Yes, that is exactly what gyroscopic effect means, the wheels try to keep straight up by theirselves, if you lean the bike you need to keep some force (your weight outside the contact patch to cause a turn/momentum wich counteract the gyroscopic effect) to keep the bike leaned.

https://www.youtube.com/watch?v=8H98BgRzpOM

Notice he moves the wheel straight up. It does not go up by itself.
The faster it spins the harder it is to move the angle but he could easily take the wheel standing up, move it to a horizontal position and it would happily spin that way. It would not stand up by itself.

a spinning wheel does automatically 'want to stand up' ....

Stand up relative to what? Center of the earth?
In space which way does the wheel consider up?

Increase the wheel's diameter?

Yea tire isnt flat, diameter of the wheel changes depending on lean angle.

and first time I leaned a street bike on a fast corner I got really scared when the bike didn´t want to be leaned and I almost went off road

Because you did not countersteer, the way you steer a motorcycle at speed.

Countersteering starts coming into effect at around 30km/h.

[Andres125sx]

Yes, that is exactly what gyroscopic effect means, the wheels try to keep straight up by theirselves, if you lean the bike you need to keep some force (your weight outside the contact patch to cause a turn/momentum wich counteract the gyroscopic effect) to keep the bike leaned.

https://www.youtube.com/watch?v=8H98BgRzpOM

Notice he moves the wheel straight up. It does not go up by itself.
The faster it spins the harder it is to move the angle but he could easily take the wheel standing up, move it to a horizontal position and it would happily spin that way.

Obviously, otherwise leaning/cornering would not be possible. But now imagine, instead of a 2kg bicycle wheel spinning at 100rpm, a 6kg motorcycle wheel spinning at 2000rpm... or even better, imagine two of them at the same time. Instead of causing a gyroscopic effect strong enough to keep a bicycle wheel straight up by itself, the effect is strong enough to keep a 200kg bike straight by itself

It would not stand up by itself.

Sorry but this is not correct. I guess you never watched a crash on motoGP (or any other category), where the rider fall down and the bike stand up by itself without rider, going straight into the barriers... I´ve been searching some video to show you but didn´t find any, too many bike crashes to find one of these

Stand up relative to what? Center of the earth?
In space which way does the wheel consider up?

The position where the wheel/bike built up the speed, wich normally is straight up

Because you did not countersteer, the way you steer a motorcycle at speed.

Countersteering starts coming into effect at around 30km/h.

Countersteer? What are you talking about? We´re talking about motorcycles.

BTW, in MX we corner way faster than 30km/h, so sorry but you need to find any other reason, I perfectly know how to steer a motorcycle, both in the dirt and on tarmac.

Edit: I did a search about countersteering and learnt what it means in bikes, but still disagree about your statement, the problem was not that, it was the gyroscopic effect. Countersteering helps to make fast direction changes, but you don´t need to countersteer to steer a bike, no matter at what speed, moving your body causes same effect, moving the center of mass out of the bike, causing a lean. Countersteer just make it faster as a slight handlebar movement (to move the bike to one side while your body keeps centered) is faster than moving your body out of the bike to one side while the bike keeps centered. It´s same effect, moving center of mass out of the bike.

Also, countersteer only applies to the start of the lean, once it´s leaned you can´t countersteer anymore, and that was the problem I described, I started to lean and realiced the bike was a lot heavier than usually, same body movement caused a much smaller bike movement, so countersteer would not help in that scenario, it was just a matter of the gyroscopic effect

That´s the reason off-road bikes use 21´ front rims (better for bumps), and road bikes use 19´rims or smaller, to reduce gyroscopic effects and make it easier to lean at speed.

The bike I mentioned wich I struggled to lean at first fast corner (actually the problem was changing direction on a series of consecutive corners) was a dual sport bike (Aprilia Pegaso) oriented to off-road, so it had 21´front wheel and the effect was even more noticeable than normally

[Tommy Cookers]

......A spinning wheel does not automatically want to stand straight up, it just means it wants to stay in its position meaning the faster you spin the wheel the harder it is to influence a direction change.
Thats why carbon wheels and counter rotating cranks are so good, they make the bike easier to flick from side to side.

a spinning wheel does automatically 'want to stand up' ....

ie a rotating wheel that is yawing develops a .....
roll moment proportionate to the yaw rate and directionally away from the roll displacement (lean) associated with the yaw

(and a yawing moment proportionate to the roll rate and directionally away from the roll displacement associated with yaw)

SectorOne

don't you recognise that want to stand up and 'want to stand up' have different meanings ?
had I wanted to write that a spinning wheel does automatically want to stand up I would have written it so

please feel free to read my second paragraph
the grammatical marker ie is denoting that the second paragraph is the justification (of the first statement)

[SectorOne]

Obviously, otherwise leaning/cornering would not be possible. But now imagine, instead of a 2kg bicycle wheel spinning at 100rpm, a 6kg motorcycle wheel spinning at 2000rpm... or even better, imagine two of them at the same time. Instead of causing a gyroscopic effect strong enough to keep a bicycle wheel straight up by itself, the effect is strong enough to keep a 200kg bike straight by itself

the reason the bike keeps going straight is not really because of any gyroscopic forces, its due to the angle of the front forks.
It essentially auto-corrects itself.

When a bicycle is just free rolling it want to tip over but it cant because everytime the front end tips one way it has the opposite effect of countersteering which causes the bike to stand itself up.

Sorry but this is not correct. I guess you never watched a crash on motoGP (or any other category), where the rider fall down and the bike stand up by itself without rider, going straight into the barriers... I´ve been searching some video to show you but didn´t find any, too many bike crashes to find one of these

It is correct and your own video even proves it. He has to manually pull the wheel straight up for it to maintain that position. The wheel DOES NOT move straight up by itself.

A horizontal wheel that is spinning will stay spinning horizontally without any outside force acting on it.

The reason the bike in those videos you are referring to steers by itself is again due to the angle of the front fork causing the bike to auto-correct itself. You can even do this experiment with a bicycle. Just toss it down the road and you´ll see.

The position where the wheel/bike built up the speed, wich normally is straight up

Exactly. So by now we can comfortably say a wheel does not automatically point up just because it is spinning but rather it will want to spin in whatever angle that it is set in.

Countersteer? What are you talking about? We´re talking about motorcycles.

Yea Countersteer, the first thing you learn when taking your license (at least in my country)

i.e. how to turn with a motorcycle. The fact that you did not even know about this until now but have been out riding on the streets means you are one extremely lucky individual to be alive.


Heres another guy that has no idea how to steer a motorcycle. Not sure hes even alive today.



edit: another star.

-

So to recap. A wheel that is spinning really fast will be very hard to change the angle of and it will not, i repeat will not go back to a straight up position if you were to tilt the spinning wheel say 90 degrees.

[SectorOne]

don't you recognise that want to stand up and 'want to stand up' have different meanings ?

To make the conversation easier i suggest we don´t use two identical sentences mean completely different things.

[TimW]

In a steady state limit cornering cornering situation, a bike shouldn't be able to stand back up because it has to countersteer into the turn, momentarily carving a tighter line than before. But if it is at the edge of traction, it can't.

This has been bugging since I realized this. Because you know, as most of us here thinks feeling you are right at the edge of traction in a corner is almost better than sex.

But also those MotoGP riders don't seem like they are holding back espically during qualifying.

I would like to know you guy's thoughts.

You do not need to countersteer, you can simply shift your centre of mass with body position. E.g. moving your outer leg(knee) up. This will of course move the rest of your body/ bike down a bit, but since your leg is closer to the pivot point(tire) it has a smaller lever and the overall centre of mass will go up/ out.

Balance on your left leg, arms to your sides. Now move your right leg out and you will topple over to the right. Moving the right leg out will even give a reaction force on your left leg to the left(into the turn)

[Andres125sx]

Obviously, otherwise leaning/cornering would not be possible. But now imagine, instead of a 2kg bicycle wheel spinning at 100rpm, a 6kg motorcycle wheel spinning at 2000rpm... or even better, imagine two of them at the same time. Instead of causing a gyroscopic effect strong enough to keep a bicycle wheel straight up by itself, the effect is strong enough to keep a 200kg bike straight by itself

the reason the bike keeps going straight is not really because of any gyroscopic forces, its due to the angle of the front forks.
It essentially auto-corrects itself.

Also, but they´re different effects. You´re talking about steer stability, wich is different to lean/angle stability. Both are necessary for a bike to continue rolling even without a rider onboard. Without the lean/angle stability the bike would crash to any side even if the steer is straight due to the forks angle (advance? it´s the translation from spanish, but not sure if that´s correct in english). Actually in those crashes I was talking about, the bike is leaned when the rider crash, and the bike straight up itself. Obviously the steer has no impact here, a straight steer is necessary for that to happen, but not enough

Sorry but this is not correct. I guess you never watched a crash on motoGP (or any other category), where the rider fall down and the bike stand up by itself without rider, going straight into the barriers... I´ve been searching some video to show you but didn´t find any, too many bike crashes to find one of these

It is correct and your own video even proves it. He has to manually pull the wheel straight up for it to maintain that position. The wheel DOES NOT move straight up by itself.

A horizontal wheel that is spinning will stay spinning horizontally without any outside force acting on it.

Agree, same as a vertical wheel that is spinning will stay spinning vertically without any outside force acting on it, wich is exactly the case we´re talking about with a motorcycle staying vertical by itself and needed some extra force to lean it into a corner

Countersteer? What are you talking about? We´re talking about motorcycles.

Yea Countersteer, the first thing you learn when taking your license (at least in my country)

Not here, at least in 1997 wich is when I got my motorcycle driving license

i.e. how to turn with a motorcycle. The fact that you did not even know about this until now but have been out riding on the streets means you are one extremely lucky individual to be alive.

You´re confusing theory and practice

If I don´t know the physics behind a riding technique that´s far from meaning I don´t master the technique. I´ve been riding motorcycles for many many years, I´ve even participated in a lot of motocross races for many years too, and I was not bad at all, so I´d say I know how to ride a bike mate, even if I can´t explain some technique or I have not heard the name of some technique. Specially in a language wich is not my native, and sincerely, in spanish I´ve never heard something similar to the translation of countersteer for bikes, and I´ve watched dozens of videos about riding techniques along the years...

So to recap. A wheel that is spinning really fast will be very hard to change the angle of and it will not, i repeat will not go back to a straight up position if you were to tilt the spinning wheel say 90 degrees.

90 degrees is unreal. What about 40 degrees? Fair question, you´ve agreed tilting the bike will be more difficult due to the gyroscopic effect wich is obvious for anyone who has ever riden a bike. But you continue denying it will straight up itself. I have always assumed it will, but you´re managing to make me doubt, not seriously but it´s a start

[Jolle]

Counter-steer is when you push the right handle bar away from you to go left. This makes the bike tip over, the steering then wants to push itself further into the bend en you apply pressure on the inside handle bar to keep a steady corner.

Basically, you turn the wrong way for a moment to lean the bike over. This is the best and only way to take a corner for us mortals on a street bike. Good chance you're doing this automatically without realizing.

When a bend is tightening, you push the inside handlebar away from you and when the corner is ending, you stop applying pressure on the handlebars and the bike will erect itself again, etc etc etc.