Practicing panic stops on the FJR with ABS

[azitlies]

Finally, I am still not confident applying heavy braking while in a turn. My reflex is to stand the bike up first. Having learned as a youngster first hand what happens (and how easier it is to do) when you apply brakes in a heavy lean, it is very hard for me to intentionally do this as an adult. Has anyone the experience of applying heavy braking in a lean and does the ABS really allow you to?

for this part anyways, of your post... at first I felt kind of dumb struck...

but that's because every time I teach an MSF course, we make it perfectly clear, over and over and over and over and over... yer not suppose to brake in a corner...

Let's first make this as clear as possible... of course one can brake in a corner... a big sweeper, yer not leaned over very much... of course you can apply some brakes.

But if yer leaned over somewhere towards the max... about the last thing you want to do is apply brakes. The reason is you may find yourself using more traction then what your tires have available! the result of that is... well, you know.

"does the ABS really allow you to?" Why would the ABS allow you to brake in a corner? ABS works when you are going straight, not when you are going sideways. Going sideways, the wheel is still turning, but sliding sideways. How would ABS help in those circumstances?

IMO anyway, if you misjudged your entry speed or it turns into a decreasing radius turn, stand the bike up and brake, then resume the corner. And work on a better entry speed.

 

[MajBach]

Finally, I am still not confident applying heavy braking while in a turn. My reflex is to stand the bike up first. Having learned as a youngster first hand what happens (and how easier it is to do) when you apply brakes in a heavy lean, it is very hard for me to intentionally do this as an adult. Has anyone the experience of applying heavy braking in a lean and does the ABS really allow you to?

for this part anyways, of your post... at first I felt kind of dumb struck...

but that's because every time I teach an MSF course, we make it perfectly clear, over and over and over and over and over... yer not suppose to brake in a corner...

Let's first make this as clear as possible... of course one can brake in a corner... a big sweeper, yer not leaned over very much... of course you can apply some brakes.

But if yer leaned over somewhere towards the max... about the last thing you want to do is apply brakes. The reason is you may find yourself using more traction then what your tires have available! the result of that is... well, you know.

"does the ABS really allow you to?" Why would the ABS allow you to brake in a corner? ABS works when you are going straight, not when you are going sideways. Going sideways, the wheel is still turning, but sliding sideways. How would ABS help in those circumstances?

IMO anyway, if you misjudged your entry speed or it turns into a decreasing radius turn, stand the bike up and brake, then resume the corner. And work on a better entry speed.

No offence, but I don't believe the answer is as obvious as you imply. The reason why braking in a corner causes the tires to 'lock up' easier is because so much of the force is now lateral instead of longitudinal (which makes the tires rotate). It's just like the the hand brake on a front wheel drive car. Pulling on the brake while driving a straight line and it is difficult to lock up the wheels. Pulling with the same force while turning the car and the rear wheels lock easily. Again, it is due to the fact that there is less force turning the wheel while in the turn and more towards the side of the wheel. For this reason, I would suspect ABS to be very beneficial in a turn and the remark "Why would the ABS allow you to brake in a corner? ABS works when you are going straight, not when you are going sideways" is old school thinking and not at all logical. I have never slid 'sideways' on a street motorcycle while in a turn but I have made plenty of turns. So, ABS will not help you if you are skidding (ie, sliding)90 degrees to the direction the bike is pointed but the moment there is ANY forward travel, the wheel want will turn. Applying the brake counteracts this turning force. Apply too much brake and the wheel locks, the ABS kicks in and stops pressure to the brakes (this is EASILY observed on any all-wheel drive vehicle taking an icy turn too fast with a little brake - the back end locks up instantly and abs kicks in). By that logic, I would expect that ABS would work 'stellarly' while in a turn since it would active much sooner with the same braking lever pressure than not not in a turn. I've just never tried it.

My inquiry was based not upon misjudging a turn but by a recent experience when a deer jumped out in front of me whilst in one. Had there been a car coming the other way, I would not have had the option to straighten up and apply the brakes.

 

[wfooshee]

On a complete side note, motorcycles don't stay upright by gyroscopic force from rotating wheels. They stay up by steering in the direction they're about to fall, and putting the wheels back under the center of gravity. Leaning to turn is nothing more than almost falling, but keeping the bike headed into the fall. To stop the turn, you steer TOWARDS the lean (by pressing the upper handlebar) it to bring the wheels back under the bike and stop falling that direction.

So if you lock a wheel, the bike will fall (DAMHIK,) but it's not because it lost a gyroscope. It's because you can't steer locked wheels, so you can't control where the center of gravity ends up. When it's off to one side, the bike goes bonk to that side.

And to the OP, there was a bike called the FJ prior to the FJR, so the stuff about older FJs was not a joke, it was useful information about a different motorcycle model.

Completely disagree with this statement. Rigidity in space from gyroscopic force does keep a bike doing what it is presently doing. This is why a bike wants to stand up in a turn if you take pressure off the bars: i.e., the plane of rotation of the tires are carving an arc through the turn (in other words, an acceleration) and gyroscopic precession (the law that a force applied to a spinning object is manifested 90 degrees in the direction of rotation from the point where the force was applied)lifts the bike back up. This is the opposite effect but same principle as how counter steering works. In your theory, a bike would fall over if in fact it was on a tread mill traveling the opposite direction to the bike's wheels (say 150 mph) and there was no relative movement to the ground. In reality, the bike would stand since the wheels moving at 150 mph would provided enough rigidity.

To continue the complete hijack, two really big issues with your thinking here: gyroscopic precession affecting the bike, and the 150-mph treadmill being motionless.

The "return-to-center" action of removing pressure from the bar while turning comes from the combination of rake and trail, not from gyroscopic precession. Find one of those BMX bikes that can spin the front wheel 360 degrees and see how it handles. Move the axle behind the steering axis and just see what happens.

If gyroscopic precession affected a bike's handling, then single-sided swingarms would never work. All the bike's weight is carried on one side of your "gyroscope" and it would spend all its time trying to turn.

Next time it's raining while you're out with your buds, watch the tire tracks in the water on the road. You'll find that they oscillate back and forth over the actual direction of travel, an indication of steering input being used to center the wheel track under the bike. A "gyroscopically" locked biked would be rock steady in direction.

And your "motionless" bike on a 150-mph treadmill is not motionless at all, it's "moving" at 150 mph relative to the surface it's riding on, and is perfectly able to steer into the lean to return the wheels under the center of gravity. Who cares if it's motionless to the ground? It's not riding on the ground!

To test your gyroscopic stability, take your bike to a dyno shop and refuse to let them tie it down, just strap it to something behind so it can't pull off the dyno wheel. Run it up to speed and see how long it stays up by itself.

All of that said, I think I mostly agree with you on your ABS argument. Keep in mind, however, that ABS keeping the wheel rolling does not remove the change in balance that results from the braking application. You still get weight transfer to the front, so even if the wheel doesn't lock you could still overwhelm the available traction if you're already turning pretty hard. Also keep in mind that ABS does not increase braking ability. It merely keeps the wheel from locking, which allows you to keep steering, which in turn allows you to keep the wheels under the center of gravity. If you're stopping hard enough to be in ABS, then you're stopping longer than best-possible threshold braking. You have to be, because ABS works by releasing the brakes!

 

[MajBach]

On a complete side note, motorcycles don't stay upright by gyroscopic force from rotating wheels. They stay up by steering in the direction they're about to fall, and putting the wheels back under the center of gravity. Leaning to turn is nothing more than almost falling, but keeping the bike headed into the fall. To stop the turn, you steer TOWARDS the lean (by pressing the upper handlebar) it to bring the wheels back under the bike and stop falling that direction.

So if you lock a wheel, the bike will fall (DAMHIK,) but it's not because it lost a gyroscope. It's because you can't steer locked wheels, so you can't control where the center of gravity ends up. When it's off to one side, the bike goes bonk to that side.

And to the OP, there was a bike called the FJ prior to the FJR, so the stuff about older FJs was not a joke, it was useful information about a different motorcycle model.

Completely disagree with this statement. Rigidity in space from gyroscopic force does keep a bike doing what it is presently doing. This is why a bike wants to stand up in a turn if you take pressure off the bars: i.e., the plane of rotation of the tires are carving an arc through the turn (in other words, an acceleration) and gyroscopic precession (the law that a force applied to a spinning object is manifested 90 degrees in the direction of rotation from the point where the force was applied)lifts the bike back up. This is the opposite effect but same principle as how counter steering works. In your theory, a bike would fall over if in fact it was on a tread mill traveling the opposite direction to the bike's wheels (say 150 mph) and there was no relative movement to the ground. In reality, the bike would stand since the wheels moving at 150 mph would provided enough rigidity.

To continue the complete hijack, two really big issues with your thinking here: gyroscopic precession affecting the bike, and the 150-mph treadmill being motionless.

The "return-to-center" action of removing pressure from the bar while turning comes from the combination of rake and trail, not from gyroscopic precession. Find one of those BMX bikes that can spin the front wheel 360 degrees and see how it handles. Move the axle behind the steering axis and just see what happens.

If gyroscopic precession affected a bike's handling, then single-sided swingarms would never work. All the bike's weight is carried on one side of your "gyroscope" and it would spend all its time trying to turn.

Next time it's raining while you're out with your buds, watch the tire tracks in the water on the road. You'll find that they oscillate back and forth over the actual direction of travel, an indication of steering input being used to center the wheel track under the bike. A "gyroscopically" locked biked would be rock steady in direction.

And your "motionless" bike on a 150-mph treadmill is not motionless at all, it's "moving" at 150 mph relative to the surface it's riding on, and is perfectly able to steer into the lean to return the wheels under the center of gravity. Who cares if it's motionless to the ground? It's not riding on the ground!

To test your gyroscopic stability, take your bike to a dyno shop and refuse to let them tie it down, just strap it to something behind so it can't pull off the dyno wheel. Run it up to speed and see how long it stays up by itself.

All of that said, I think I mostly agree with you on your ABS argument. Keep in mind, however, that ABS keeping the wheel rolling does not remove the change in balance that results from the braking application. You still get weight transfer to the front, so even if the wheel doesn't lock you could still overwhelm the available traction if you're already turning pretty hard. Also keep in mind that ABS does not increase braking ability. It merely keeps the wheel from locking, which allows you to keep steering, which in turn allows you to keep the wheels under the center of gravity. If you're stopping hard enough to be in ABS, then you're stopping longer than best-possible threshold braking. You have to be, because ABS works by releasing the brakes!

Some good points. I will need to digest (and open up some old mechanical engineering textbooks - I actually kept them).

Note: I am not saying I agree with you...yet.

 

[azitlies]

Question: How would an ABS sensor know when to kick in the ABS if the tire is still turning?

Answer: It doesn't.

Point: When one is going around a corner, say at the max lean angle (using all available traction) the tires are still turning. If you try to slow down now using the brakes it will result trying to use more traction then whats available, thus a sideways, or lateral skid (the tires slide out from under you - AKA Low Side). ABS is not going to sense this.

No offense, but this isn't "old school", it's a simple obvious fact, to most people anyway.

 

[ionbeam]

Question: How would an ABS sensor know when to kick in the ABS if the tire is still turning?

Answer: It doesn't...

More info on ABS 'kick in'.

 

[wfooshee]

Question: How would an ABS sensor know when to kick in the ABS if the tire is still turning?

Answer: It doesn't.

Point: When one is going around a corner, say at the max lean angle (using all available traction) the tires are still turning. If you try to slow down now using the brakes it will result trying to use more traction then whats available, thus a sideways, or lateral skid (the tires slide out from under you - AKA Low Side). ABS is not going to sense this.

No offense, but this isn't "old school", it's a simple obvious fact, to most people anyway.

True, but not many of us are constantly on that max available traction point. Even when we think we are.

But anybody that watches motorcycle racing has seen what you're describing. Bike diving into the turn tipped in, still got some brakes, then BAM!!! He's on his side. No smoke, no skid, no locked wheel, the rider just went outside the traction circle.

 

[azitlies]

True, but not many of us are constantly on that max available traction point. Even when we think we are.

But anybody that watches motorcycle racing has seen what you're describing. Bike diving into the turn tipped in, still got some brakes, then BAM!!! He's on his side. No smoke, no skid, no locked wheel, the rider just went outside the traction circle.

Of course. Certainly don't mean to imply "many of us are constantly on that max available traction point".

Only trying to make something obvious, and that is when we're cornering, the traction available is now on the side of the tire. Cornering too hard, or braking too hard when leaned over, or a combination of the two does not cause the tire to "lock up". It causes it to skid sideways, laterally. As you say "go outside the traction circle".

ABS is not going to sense this.

 

[MajBach]

Question: How would an ABS sensor know when to kick in the ABS if the tire is still turning?

Answer: It doesn't.

Point: When one is going around a corner, say at the max lean angle (using all available traction) the tires are still turning. If you try to slow down now using the brakes it will result trying to use more traction then whats available, thus a sideways, or lateral skid (the tires slide out from under you - AKA Low Side). ABS is not going to sense this.

No offense, but this isn't "old school", it's a simple obvious fact, to most people anyway.

No offense but it's neither obvious nor a fact. Enlightened people understand that ABS is not all or nothing and that is is computer controlled, not mechanically as it once was, i.e old school.

 

[MajBach]

True, but not many of us are constantly on that max available traction point. Even when we think we are.

But anybody that watches motorcycle racing has seen what you're describing. Bike diving into the turn tipped in, still got some brakes, then BAM!!! He's on his side. No smoke, no skid, no locked wheel, the rider just went outside the traction circle.

Of course. Certainly don't mean to imply "many of us are constantly on that max available traction point".

Only trying to make something obvious, and that is when we're cornering, the traction available is now on the side of the tire. Cornering too hard, or braking too hard when leaned over, or a combination of the two does not cause the tire to "lock up". It causes it to skid sideways, laterally. As you say "go outside the traction circle".

ABS is not going to sense this.

Bull**** x 2

 

[azitlies]

Enlightened people? lmao, thanks for the laugh

maybe you could enlighten us then? explain how the computer controlled can sense the tire is skidding laterally, even though the tire is still turning, and what does it do about it?

 

[ionbeam]

...explain how the computer controlled can sense the tire is skidding laterally...

Click the link in post #45 and give it a quick scan.

 

[chivvalry]

However, slowing to stop at a stop sign, keeping the REVS up on the motor will create gyroscopic forces that can let you come to a complete stop with both feet on the pegs, wait for a 4-count, then drive off from a complete stop without ever putting down a foot. All that rotational mass in the motor spinning around 3k rpm WILL help hold the bike upright. Of course, a big fat, FLAT rear tire helps.

No sh1t?? That really work or is it that big fat car tire back there that's doing all the balancing for you? Gonna run out right now for lunch and try and balance like a ninja on my gyroscope... :assassin:

Oh, and I have engaged ABS on my bike several times... AND IT FREAKING ROCKS! I have NEVER stopped so fast on a bike before ABS...

 

[azitlies]

...explain how the computer controlled can sense the tire is skidding laterally...

Click the link in post #45 and give it a quick scan.

"When a wheel is braked to the point of slipping (lock-up) the ratio of wheel speed to chassis speed becomes out of balance. A skid or wheel lock-up is when the chassis has enough inertia to overcome the available tire traction when braking."

But the braking isn't causing the tire to "lock-up". The tire is sliding sideways because of lateral force, but the wheel is still turning, not skidding or locking up with forward momentum. The information you cite sounds more specific to cars?

Wheel speed isn't changing when the bike is sliding sideways (on the sides of the tires) is it? The wheel is still turning. The wheel will continue to turn, even after lateral traction is lost, and we all know what happens next.

 

[RadioHowie]

Wheel speed isn't changing when the bike is sliding sideways (on the sides of the tires) is it? The wheel is still turning. The wheel will continue to turn, even after lateral traction is lost, and we all know what happens next.

The ABS "kicks in" when the speed of one wheel is different than the speed of the other wheel while the brakes are applied.

So assuming one wheel is sliding sideways, it's turning slower than the wheel that isn't sliding, so the ABS WOULD activate on the sliding wheel.

 

[chivvalry]

However, slowing to stop at a stop sign, keeping the REVS up on the motor will create gyroscopic forces that can let you come to a complete stop with both feet on the pegs, wait for a 4-count, then drive off from a complete stop without ever putting down a foot. All that rotational mass in the motor spinning around 3k rpm WILL help hold the bike upright. Of course, a big fat, FLAT rear tire helps.

No sh1t?? That really work or is it that big fat car tire back there that's doing all the balancing for you? Gonna run out right now for lunch and try and balance like a ninja on my gyroscope... :assassin:

Oh, and I have engaged ABS on my bike several times... AND IT FREAKING ROCKS! I have NEVER stopped so fast on a bike before ABS...

Okay... I felt no difference in balance with revs at idle or revs at 3 or 4k. Except that I felt kinda funny with my engine rev'd up at a stop sign... :glare:

 

[azitlies]

Okay, here's a link that should clear this up:

Honda Engineer

This quote is from 2008, and Honda is developing (has developed?) an ABS system that should help with the scenario we are discussing... it uses gyroscopes to accomplish it.

ABS while cornering - no, it doesn't help, says Honda

For the benefit of all those who were certain it did, and ignored the

point that when tyres let go under cornering, they sideslip (and ABS

doesn't control that)...

 

Article in this week's Motor Cycle News, page 10. Honda is developing

a new ABS system that will work under cornering. It uses gyroscopes.

 

Quote from the paper: "Current ABS systems stop tyres locking up when

a bike is upright, but cannot tell when braking causes the tyre to

slide sideways, as it would if you panic brake while the bike is leant

over."

 

Quote from Kazuhiko Tani, Honda's chief ABS engineer, interviewed by

the paper: "The system... will take the added control we can get in a

straight line and add control under braking while the motorcycle is

cornering. The most difficult part of getting a bike to corner and

brake while maintaining control is making sure the lateral forces and

grip are not overwhelmed by the braking forces."

 

So there you have it. If you want to argue the point futher, take it

up with Tani, but I'll stick with his opinion.

 

[SkooterG]

Nice find azitlies!

 

[MajBach]

Okay, here's a link that should clear this up:

Honda Engineer

This quote is from 2008, and Honda is developing (has developed?) an ABS system that should help with the scenario we are discussing... it uses gyroscopes to accomplish it.

ABS while cornering - no, it doesn't help, says Honda

For the benefit of all those who were certain it did, and ignored the

point that when tyres let go under cornering, they sideslip (and ABS

doesn't control that)...

 

[...]

 

So there you have it. If you want to argue the point futher, take it

up with Tani, but I'll stick with his opinion.

Further down in that same article:

Nobody ever claimed that it would stop a sideways slide. It won't on

a car either. So what?

and

Agreed. Pretty clearly, loss of traction occurs when a wheel

stops rotating and this is what ABS is intended to prevent.

 

Quite possible that the addition of a gyroscopic sensor to

sense lateral forces improves traction while cornering and

braking, but this is a far cry from "ABS doesn't work in a

corner".

 

Sounds more like an appeal to authority than a technical

argument. What I read is that Honda has what they claim

is an improvement to ABS technology.

and

OK. You're simplistic.[old school]

 

Seems as if a more accurate statement would be that

it ***sometimes*** doesn't prevent loss of traction and

that Honda has improved on the design.

 

Beware of absolutes like "doesn't work".

 

What kind of corner ? How far over is the bike leaned ?

 

Anybody care to argue that the article "proves" conventional

ABS never works in a corner ?

All this outdated article (read: post) does is illustrate that this is not the first forum where this debate has occurred. I would further suggest that points quoted in that article have no more merit than the ones here since idea that "Current ABS systems stop tyres locking up when

a bike is upright, but cannot tell when braking causes the tyre to slide sideways" is not shown to be stated by an engineer from Honda, who, might just be tooting his company's own horn anyway.

 

[SkooterG]

Yo Maj - you are quoting comments from the peanut gallery that mean absolutely nothing. And I'm sorry, that article 'illustrates' a lot more than forum debates and the info from a Honda engineer who develops motorcycle ABS systems has a lot of 'merit' for me.