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Andy VH
Where is the earth shattering kaboom!?



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   Posted 12/13/2011 8:03 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Have you noticed that all the motorcycle ABS videos show the bike stopping in a straight line? On dry pavement, on wet pavement, with sand on the pavement, all the videos I have ever seen only show the bike stopping in a straight line. Sure, there are lots of videos of bike wihtout ABS, but equipped with outriggers, locking up the tires in a straight line stop and violently flopping to an outrigger to keep the rider from injury. But even in those videos, I bet a few test riders have almost been pitched off the bike when it suddenly flops onto the outrigger support, or when the bike spins in a circle leaning on the outrigger.
 
Yet, videos of cars stopping with ABS brakes, often show the car being steered around an obstacle even when the brakes are simply tromped on full, and the driver can "steer" to some degree to control the car.
 
Difference is, ABS brakes on a bikes are really only effective for upright, straight line stops. I have not yet found any test or study report for ABS stops while swerving/turning on a bike. It comes down to a basic control principle of ABS brakes, for cars, motorcycles, trucks, airplanes. They're all closely similar, as they all depend on the ABS braked wheel actually "slipping/skidding" 10% to 20% slower in rotational speed than the actual vehicle speed. Without that slip/skid factor, effective ABS braking is not achieved. But that also means, the ABS control does not even occur until a wheel has actually started skidding, with the brake applied. So that means traction is already being used, a LOT of traction, just to get the ABS control engaged. Now if you were to combine the traction needed to swerve, lean or turn the bike, and the traction limit is very likely exceeded, WITH ABS or not.
 
It is possible, on dry pavement, to dump a bike just by excessive, aggressive swerving. The traction load is so great just to maintain a swerve, that to expect ABS braking during a swerve will certainly overcome the traction limit. And I doubt ABS will allow enough traction to be regained, in time, to maintain directional control, without some fairly violent chassis/rider reactions. This goes along with the post "Know what your ABS system CANNOT do", to make it clear that ABS on a cycle is not used like ABS on a car. The results in a straight line are good and beneficial. There "may" be slight control/stability benefit to ABS applied during a very slight lean. But I'd bet the results during swerving/leaning/turning could be anything but what most everyone expects ABS on a bike would do for them. Good braking technique, good swerving technique, good control technique ALWAYS has priority over expecting ABS to save your hide.  


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Post Edited (Andy VH) : 12/16/2011 3:59:19 PM GMT

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thesoapster
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   Posted 12/13/2011 9:18 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I like having a good feeling of control with either brake and non-interference. As you said, ABS is definitely designed for the straight up and down panic braker. We've all done it at least once. However there are times when I need to brake (or at least initiate it) in a corner with a decent lean. I guess you'd have to jam into the front brake pretty hard to engage the rear, would you not? That's a pretty big no-no on any bike!
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Andy VH
Where is the earth shattering kaboom!?



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   Posted 12/14/2011 5:25 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Depends on how hard you come into the corner, how much the rear tire is unloaded due to weight transfer, and how sensitive the ABS system is to wheel speed differences (front to rear) while braking. ABS does nothing but monitor wheel speed if the brakes are not applied. A lot of people think ABS works the minute they apply any brake. Not so. The wheel speed differential thresehold has to be achieved before ABS control engages. Its in that time sequence of leaned over, brake applied, and then finally the braked wheel achieves the differential thresehold, that ABS control begins. 

The ABS control is totally independent for the front and rear wheel. You can apply enough front brake force to engage ABS on the front wheel, and it will have NO effect at all on the rear wheel. Again, for ABS control to engage on either wheel, the brake for that wheel must be applied, and the speed differential thresehold has to be met or exceeded. "Linked ABS" systems should not be confused with linked brakes. On linked brake systems a portion of the other brake is applied if only the front or rear brake is applied. A linked ABS system is used to offer traction control, anti-wheelie control and anti-stoppie control, in order to maintain bike stability. Linked ABS does not apply braking, or ABS control, to a wheel on which the brake is not applied. For instance, with Linked-ABS, if your front brake is applied and the wheel skids, and ABS engages on that wheel, it does not apply ABS wheel control to the rear wheel also.

If so inclined, you could apply a lot of rear brake in mid-corner, and get ABS control to engage. BUT! If leaned into a corner a lot of traction is already used up, even for the rear tire. Then if braking is added and the rear wheel begins to lock (while leaned over, which we all know is bad), the rear wheel ABS might engage but the rear of the bike may already have "stepped out" enough for the bike to lowside. Or worse, if ABS does engage and the rear suddenly gains traction, a high side is very possible. Since high sides can happen SO quick, and the action can be so violent, that few riders can regain control from it.


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Post Edited (Andy VH) : 12/14/2011 12:32:39 PM GMT

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GeoffG
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   Posted 12/14/2011 2:33 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy, your scenario about high-siding if ABS were to allow a rear tire that was stepping out to suddenly regain traction, sounds valid to me. Indeed, for that reason alone I'd be leery of ABS on the rear wheel of a bike.

The main difference between bikes and cars, where ABS is concerned, is that a car CAN endure intermittent traction while braking and cornering without falling over.

I don't think it's uncommon for experienced riders to brake while cornering (indeed, "trail braking" is an invaluable track skill). However, you don't want to approach front wheel lockup while doing so--and unless you're at or near lockup, ABS won't be operative. Should you lockup, though (due to a sudden change in traction, say an oil spill), ABS might help...hmmm...I dunno, it'd depend on all kinds of factors.

Personally, my own bike doesn't have ABS, and I'm happy with that. I'm not against ABS, but I wouldn't necessarily use it as criteria for buying a bike.
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thesoapster
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   Posted 12/14/2011 3:48 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
I thought linked systems specifically were designed to add rear brake to heavy handed front braking, though never adding front with rear braking alone.
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Andy VH
Where is the earth shattering kaboom!?



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   Posted 12/14/2011 7:51 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Most linked brake systems, like those on some Guzzis, Gold Wings, BMW K1200LT and some others, are intended to aid braking effort for riders of those bikes who tend to be more rear-brake style riders. In order to insure those big heavy bikes stop straight and quickly enough, if the rear brake alone is applied, a hydraulic splitter/proportioning system applies some of the front brake even if the rider does not. Likewise, if the rider applies only the front brake, the system also applies the rear brake. Again, this is intended mostly to aid braking stability.

Honda's VFR has a system which is a blended integrated/linked/ABS system. The VFR has six piston calipers on the front brakes, and the system actually applies different combinations of caliper pistons, along with the rear brake, or front brake, depending on control logic built into the controller. The early system was complicated and "iffy" on functionality. But the revised system is highly regarded for braking capability and bike stability.

As to the scenarios described for the limits of ABS when leaned, my intent is to make riders aware that ABS on cycles and cars operate on very similar control principles, but ABS on a motorcycle that must lean in turns changes a LOT of what ABS cannot be expected to do. In that respect, ABS use on cycles is VERY different than ABS on cars. ABS equipped test bikes with outriggers exist, but yet I have never seen a video or article about such a bike tested to demonstrate what the results of ABS control on a leaned over motorcycle would be.


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Post Edited (Andy VH) : 12/15/2011 2:57:58 AM GMT

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louemc
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   Posted 12/15/2011 1:25 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy VH said...
Have you noticed that all the motorcycle ABS videos show the bike stopping in a straight line? On dry pavement, on wet pavement, with sand on the pavement, all the videos I have ever seen only show the bike stopping in a straight line. Sure, there are lots of videos of bike wihtout ABS, but equipped with outriggers, locking up the tires in a straight line stop and violently flopping to an outrigger to keep the rider from injury. But even in those videos, I bet a few test riders have almost been pitched off the bike when it suddenly flops onto the outrigger support, or when the bike spins in a circle leaning on the outrigger.
 
Yet, videos of cars stopping with ABS brakes, often show the car being steered around an obstacle even when the brakes are simply tromped on full, and the driver can "steer" to some degree to control the car.
 
Difference is, ABS brakes on a bikes are really only effective for upright, straight line stops. I have not yet found any test or study report for ABS stops while swerving/turning on a bike. It comes down to a basic control principle of ABS brakes, for cars, motorcycles, trucks, airplanes. They're all closely similar, as they all depend on the ABS braked wheel actually "slipping/skidding" 10% to 20% slower in rotational speed than the actual vehicle speed. Without that slip/skid factor, effective ABS braking is not achieved. But that also means, the ABS control does not even occur until a wheel has actually started skidding, with the brake applied. So that means traction is already being used, a LOT of traction, just to get the ABS control engaged. Now if you were to combine the traction needed to swerve, lean or turn the bike, and the traction limit is very likely exceeded, WITH ABS or not.
 
It is possible, on dry pavement, to dump a bike just by excessive, aggressive swerving. The traction load is so great just to maintain a swerve, that to expect ABS braking during a swerve will certainly overcome the traction limit. And I doubt ABS will allow enough traction to be regained, in time, to maintain directional control, without some fairly violent chassis/rider reactions. This goes along with the post "Know wht your ABS system CANNOT do", to make it clear that ABS on a cycle is not used like ABS on a car. The results in a straight line are good and beneficial. There "may" be slight control/stability benefit to ABS applied during a very slight lean. But I'd bet the results during swerving/leaning/turning could be anything but what most everyone expects ABS on a bike would do for them. Good braking technique, good swerving technique, good control technique ALWAYS has priority over expecting ABS to save your hide.  

 
Totally agree Andy...The way ABS is hyped  (in my way of looking at things), is fraudulently creating a dangerous frame of mind, in bike safety.
 
I can't help but think a roaring majority of buyers...feel a situation is lurking out there, that they won't be able to handle, and the ABS will come through, no matter what or how or  where  the situation comes up.
 
The Hype never mentions something....there is more to braking, than whether or not a tire is skidding...
 
The rider has to know when they can brake...and when they can't...and if braking how much, on what type of surface.  
When the biker knows how to brake...ABS can assist...But when the biker doesn't bother to learn...that biker can very easily put the bike in a situation that can't be fixed.


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Andy VH
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   Posted 12/15/2011 4:42 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
A huge influence on the misperception of ABS is in the name itself "Antilock Braking System". Everyone assumes it is a braking system, or a braking assist system, which it is NOT. Had it been called a "Stability Assist System" from day one with no reference to braking, then perhaps over time the car drivers and bike riders would not first think of ABS as a braking system.

"Stability", whether applied to the dynamics of a car or motorcyle, in essence means the operator is able to maintain control over the vehicle. But especially on a motorcycle, stability also means the bike must first remain upright, or at least in a manner enough for the rider to maintain control. For example: a rider power sliding through a turn, the bike can be leaned over a LOT, and countersteered a LOT, but yet the bike is stable because the rider has control. So the FIRST and PRIMARY function of ABS on cycles is to maintain stability/control, and in so doing the current ABS systems only fulfill this directive when the bike is stopped in a straight line and nearly always fully perpendicular to the road surface.

When we consider traction control systems for high performance riding, its been proven on race tracks that for a bike to really be fast through the turns the rider must be able to spin/slide the rear tire, sometimes with the rear of the bike stepping out. Traction Control, as a stability control, actually limits the rider's ability, if indeed the rider is skilled enough to power slide on dry pavement through turns.

So back to ABS, it is ONLY a stability assist system. In that context, riders really should not expect the ABS system to overcome their mistakes and inabilities relative to maintaining control while leaned into a turn and applying brakes. Because it all comes down to the traction limits. If the rider exceeds the traction limits while leaned/turning, the ABS system very likely cannot always assist the rider to maintain or regain control. Remember, for ABS to even engage, the rider first has to be on the brakes, and the tire has to slightly exceed the traction thresehold, which most all of us know is NOT a good stable condition when leaned over and using traction already.

As an example, I have posted a similar discussion on the BMW owners website. I got a response from a fellow rider saying, "But, if you're not quite to that point (of loosing traction) and slowing down can help, ABS is good and brake locking isn't." His comment is exactly what I mean to clarify. His comment indicates he expects ABS to help him when braking (ABS is good and brake locking isn't), which is NOT the case. ABS does NOTHING until traction is exceeded. Most everyone seems to miss that critical point, traction HAS to be exceeded in order for ABS to engage control. Without breaking traction, ABS is just along for the ride doing nothing.


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Post Edited (Andy VH) : 12/16/2011 4:05:42 PM GMT

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RaptorFA
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   Posted 12/18/2011 7:44 AM (GMT -7)    Quote This PostAlert An Admin About This Post.

I have ABS brakes on my bike, and I love the system, make no mistake. And it has come in very handy in certain situations no doubt. But I certainly have no delusions about how ABS is going to save me in an extreme situation while leaned over or where traction limits have been exceeded to an extreme degree over a non ABS equipped machine. It can help out under certain "non straight up" circumstances but the aid is minimal. In other words having ABS is no substitute for good braking technique. To borrow a phrase, "ABS does not mean automatic braking system"! I am finding that traction is king, and just because I have ABS, this does not mean I have any distinct advantage in the conditions described above. It could help, but good instincts and technique is what is going to save my bacon. Still, I like the system and I'm glad it is there.

  

 


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RaptorFA
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thesoapster
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   Posted 12/18/2011 8:31 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
Because ABS only works when on the brakes, what you're referring to, Andy, is meant to be combatted by TC/throttle control/both. Look at the BMW. You get the whole package together pretty much because of what you said.
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GeoffG
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   Posted 12/19/2011 11:20 AM (GMT -7)    Quote This PostAlert An Admin About This Post.
And, of course, it had to happen. This guy is suing Harley because he locked the rear tire on his bike and crashed (badly injuring his passenger)--apparently it's Harley's fault because he thought the bike had ABS...

www.sacbee.com/2011/12/16/4126504/contentious-motorcycle-accident.html#storylink=omni_popular







On a completely different note--Andy, I disagree that "ABS" is a misnomer. It accurately describes what the system does--it prevents prolonged brake locking (thus, Anti-lock Braking System). And it DOES help people brake more effectively--in cars, on slick surfaces, especially when driven by average people (ie, not rally drivers). Keep in mind that when the system was first introduced, it was in the automobile market, not bikes. (I do agree that perhaps on bikes it might be called something else...but just because people don't understand what it does, doesn't make the system bad--however, I'd hesitate to call it a "stability system," because that'd make people even more likely to think it'd magically keep them upright...)
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Andy VH
Where is the earth shattering kaboom!?



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   Posted 12/19/2011 1:24 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Potatoe, patatoe,.....I understand your rationale, and yes the ABS does exactly what it is called. But consequently everyone only considers it a braking assist system.

Unfortunately in this "It's NOT MY fault!" society, it matters little what you name anything. Nothing is idiot proof, and for every idiot operating something it seems there is legal representation just waiting to tell him he had no fault in doing it wrong.

I reviewed that article about the couple crashing their Harley. Terrible that anyone should crash and suffer traumatic injury. But to read that he crashed the bike when the rear tire locked up speaks volumes to his lack of skill. Yes, at first it seems disturbing that the ABS icon is on all the tachometers of that model, even if the bike did indeed NOT have ABS. But I agree with the later comment that he should be aware of what his bike is fitted with in 12,000 miles and 15 months of ownership! C'mon pal, be honest, you never ever questioned why the ABS light didn't ever come on? More yet, you never tested your bike to see how the brakes worked to find out how you perform? If I were on the jury I have to say I would be siding more with HD than the couple. In my book, no matter how your bike is set up, YOU HAVE TO KNOW IT AND PRACTICE IT. If not, then you simply should not be riding.


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Post Edited (Andy VH) : 12/19/2011 8:34:10 PM GMT

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GeoffG
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   Posted 12/19/2011 9:32 PM (GMT -7)    Quote This PostAlert An Admin About This Post.
Andy VH said...

I reviewed that article about the couple crashing their Harley. Terrible that anyone should crash and suffer traumatic injury. But to read that he crashed the bike when the rear tire locked up speaks volumes to his lack of skill. Yes, at first it seems disturbing that the ABS icon is on all the tachometers of that model, even if the bike did indeed NOT have ABS. But I agree with the later comment that he should be aware of what his bike is fitted with in 12,000 miles and 15 months of ownership! C'mon pal, be honest, you never ever questioned why the ABS light didn't ever come on? More yet, you never tested your bike to see how the brakes worked to find out how you perform? If I were on the jury I have to say I would be siding more with HD than the couple. In my book, no matter how your bike is set up, YOU HAVE TO KNOW IT AND PRACTICE IT. If not, then you simply should not be riding.

Just read that the jury came back FOR Harley--the rider was found to be at fault. I agree, the case was ridiculous on the face of it. As I said in another forum (where I first read of this), increased skill and better situational awareness would likely have prevented this accident more reliably than any ABS system.

A Sacramento Superior Court jury today exonerated Harley-Davidson in a lawsuit filed by a woman who suffered severe brain damage in a 2009 wreck on Highway 99. Plaintiff Judy Wilson had charged in her suit that the motorcycle her husband crashed while she was riding on the back had a defective design because of an icon on its tachometer that made him think the bike had anti-lock brakes when it didn't. Wilson also charged that a salesman for Harley-Davidson of Sacramento told her the motorcycle had an anti-locking braking system. The company argued that the design was not defective and that it's been selling motorcycle with the "ABS" icon for years without incident. The dealership denied that its salesman ever told Wilson the bike had the anti-lock braking system.
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Well Enuff
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   Posted 1/25/2012 2:38 PM (GMT -7)    Quote This PostAlert An Admin About This Post.

About a dozen years ago I read that accidents in ABS equiipped autos happened when the driver stomped on the brakes and was surprised that the steering was so effective. That caused the car to miss the threat on the road and swerve into the ditch.

Pertainting to cycles, I found this discussion at: http://www.iihs.org/research/qanda/antilock.html

Yes. Results from recent studies by the Institute and HLDI compared crash rates for motorcycles equipped with optional ABS against the same models without the option. The rate of fatal crashes per 10,000 registered vehicle years was 37 percent lower for motorcycles equipped with optional ABS than for those same motorcycles without ABS. In crashes of all severities, the frequency at which collision claims were filed was 22 percent lower for the ABS models.10,11 Based on these findings, the Institute in April 2010 petitioned the National Highway Traffic Safety Administration to require manufacturers to equip all new motorcycles with this technology.

-- end of excerpt ---

I fnd it scary the ABS might be required to be installed on all new motorcycles. I haven't followed up on the 2010 proposal, but apparently it did not get too far.

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