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ABS is buggy


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Last week, I had to make a emergency stop in order to avoid a overexcited dumbass in a Subaru STI that was lane splitting...
While I was about to repass him, he decided to quickly come in my lane...
 
Luckyly, I was already covering the front brake with two fingers, and I started to squeeze the front as hard as I could...
Then, a second later, I started to use the rear brake. I felt the rear wheel lock up, and then, all of a sudden, the ABS released both brakes !!!
 
The front was not skidding at all, only the rear, but I could feel that the ABS momentarely released BOTH brakes, for 1/4 sec or so...
 
Now, How stupid is that. >:D

Because of this glitch, I came inches from touching the rear bumber of the Subaru, and probably totaling the bike... :'(
If the ABS would have not interfere, I probably would not even need to clean my underwears.
 
 
I later practiced emergency braking in a safe place, and, it really does that. ;-|
 
Dumb ABS.
 
So, the safest way to perform an emergency stop is to ONLY use the front brake. :-S
 
Yamaha, Please Fire your brake engineers right now, and get real ones... (maybe from BMW).

 
Meanwhile, have anybody experienced this ?
 
Ride safe.
 
 
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I've locked the rear-up and had the ABS kick-in. Don't recall feeling any modulation on the front brake. You have peaked my curiosity and I will run some emergency braking tests this week.
STUFF EVERYTHING - I'VE ALWAYS GOT MY BIKE!
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While I agree that the ABS interfering with the front is unwelcome, I *think* there is a well-intentioned reason for it. A locked rear tire very easily swings out of line. If the rear ABS is fast enough it shouldn't get too far but as it releases the rear it's possible to get a strong snap as it resumes tracking the front. Think, a taste of a mini high-side. By easing/releasing the front it momentarily negates/reduces the deceleration of the bike and I expect considerably lessons said 'snap'.
 
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Not disagreeing on principal, but then why ABS? Does BMW or Ducati, or HOnda keep the rear locked? Or is their software not so 'slow' that it prevents a lockup in the first place? I'm guessing the real-deal software/sensors are more responsive. This is IMO what happens when you mandate ABS - manufacturers will spend as little as possible to comply and deliver sub-standard results. Lockups in loose surfaces (the big trailies) happens a lot so obviously there is logic in their algorithms to restore rotation. Maybe they just re-cycled the software from a TDM?
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This is the first bike that I have owned with ABS and at times I wish that it could be turned off. I've only had the ABS engage under hard straight line braking and it was quite a surprise. What I would like to understand is how the ABS and traction control systems interact. I don't have any reason to believe that the Yamaha ABS is inferior to others. Having never had ABS, I'm used to leaving the rear wheel locked rather than risk a highside on pavement. If the ABS kicks in and the wheel starts rotating what happens next? Hopefully the back end hasn't swung out and the front and rear wheels are still aligned.
STUFF EVERYTHING - I'VE ALWAYS GOT MY BIKE!
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I've definitely locked the rear without having the front go into ABS cycling, and vice versa, numerous times. I practice panic stops almost every day, often on a steep downhill where it's easy to get the rear light enough to lock and start ABS cycling. The two systems are independent as far as I can tell, although there may be interplay between them if the rear wheel lifted enough, similar to how the traction control system keeps the front wheel down. I haven't tried inducing stoppies to see what the system does. Is it possible the rear wheel lifted?
 
If not, it's quite possible that there was some brief change in traction level, though; a painted line, a manhole cover, an oil spot ... any of those could be enough to kick in the ABS. I have had a couple of crashes over the years from small but yet ultimately significant changes in traction during hard braking where I had to go back and look hard at the road surface before I figured out what went wrong.
 
In any case, if you don't do so already, I strongly recommend regular practice of maximum braking. Pick something on the side of the road, or a mark on the road, on some stretch you ride regularly. Every time you go along that route practice braking later and later and seeing how close you can get to your mark without going over. At some point you will inevitably fire the ABS system and that's a good way to get the feel for how it works.
 
During emergency braking I used to simply ignore the rear brake; I had a lot of trouble modulating the rear while simultaneously modulating the front and it was better not to use the rear than to get it skidding and lose stability. I'm happy as heck to have ABS, I just stomp away and let the electronics help keep the bike stable. Win!
2015 FJ-09 (Mary Kate)
2007 Daytona 675 (Tabitha, ret.)
1998 Vulcan 800 (Ret.)
2001 SV650S (Veronica, Ret.)
2000 Intruder 800 (Ret.)
 
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Yes, I am saying that the front brakes disengages if the rear wheel locks... ??? In emergency situations. That is what I experienced.
 
Jimf, Prior to this event, I also attempted to lock the rear wheel numerous times just for fun :D, and never noticed that the front brake was disengaging.
So you are probably right, it does not happen in "normal" situations. You really have to be close to the limit of adherence on the front brake.
At that time, there was no white lines or anything, but it could still be oil or dirt that triggered the front ABS...
 
To me, the way ABS should work the following way:
- If a difference of speed is found between front and rear wheel, release the slowest brake until speed is the same.  8-|
 
Not both brakes.  (puke)
 
Could it be related to the fact that the brakes are linked, and that when braking really hard, the ABS pressures back oil from the rear to the front brake ? 
I could reproduce the problem in a very grippy parking lot, and there is no way that I could make the front wheel skid on that surface.
The bike would rather start to make a stoppie.
 
...Speaking of stoppies, maybe that I was making a stoppie and that is what triggered the release of the front brake ?
 
BMW brakes are supposed to be superior, because :
Quote from BMW web site
 
BMW Motorrad also sets technological standards with its ABS: the highly sophisticated brake system provides assistance for the rider, ensuring that the motorcycle can be intuitively controlled even when extreme braking maneuvers are performed. This is possible due to the combination of ABS along with the optional package of traction control (DTC) and banking position measurement - something which is unique among all manufacturers.
 
 
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Could it be related to the fact that the brakes are linked, and that when braking really hard, the ABS pressures back oil from the rear to the front brake ?


Pretty sure they aren't linked in any physical way, as in linked brakes.  Engaging the front brake in no way engages the back brake nor the other way around.  I can't comment on if the ABS system is linked.
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The brakes are not linked on the Tracer.
 
The system on the Tracer is a variant of the ADVICS system used on the Super Tenere and FJR1300. On the Super Ten, the brakes are linked whereby the front brake lever actuates one piston in the rear caliper. On the Super Ten, the rear brake pedal only operates a rear brake piston.
 
I have also owned a Super Tenere.
 
In my experience, there has not been any problem with the ABS working unexpectedly on the Super Ten or Tracer. Although, I concede that whilst I have had to use the brakes in emergency situations due to other road users unpredictable behaviour, I have not locked the front brake. As jimf states, locking the rear is easy to do especially going downhill where one is using the front brake as well, the rear ABS will activate and you feel the pulses with your foot. The front wheel does not lock and there is no interference from the ABS.
 
If fred's hypothesis is correct, why have I not felt the front brake being pulsed by the ABS when locking the rear on a steep downhill gradient?
 
 
This signature is left blank as the poster writes enough pretentious bollocks as it is.
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Agree. You can engage the rear ABS without any effect on the front wheel. Probably because they have separate sensors.
and separate hydraulic circuits - there will be 2 separate pistons in the ABS pump - fred seems to be positing the theory that if the piston on the rear ABS circuit is actuated, the piston on the front will also be actuated releasing hydraulic pressure in the two separate brake circuits. I have not experienced this myself and it would not make any sense for this to happen. This is not to say that the control algorithm and or circuitry does not operate this way in some circumstances, but I am hugely skeptical as the technology is well proven in other bikes in the Yamaha range. 
This signature is left blank as the poster writes enough pretentious bollocks as it is.
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  • 1 month later...
If I remember correctly, the owners manual indicates the FJ09 has the rear brake applied when you apply the front brake lever, but then "disengages" the rear/front connection if you use the foot/rear brake during this process.
 
So, on every normal front brake use, it also applies some rear brake as determined by the ABS system. (I can confirm this as I never use the rear brake 99.9% of the time, yet my rear brake rotor is showing signs of use that it never has on any other bike I've owned, including the 2014 FZ09 I had prior to this 2015 FJ09.)
 
I also have noticed a serious difference in the rear brakes on the FZ v/s FJ. The FZ has a solid dirt bike type brake pedal, and it's very tight, very little movement needed to apply the rear brake, and you feel it even if you just bump it slightly.
 
While on the FJ, it's a long stroke, has a rubber insulated pedal, like the shifter side, and you bump it, nothing happens, you have to really want to push it, and have to apply the brake WAY more than the none ABS FZ setup.
 
But, that being said, I've panic stopped a few times on both bikes to just get the feeling for how they work, and have to say the effect of the ABS system applying the rear brake, and controlling/modulation of that rear brake in concert with the front brake that I'm happy to apply and control works best. (This bike stops on dime, sure better pads might make it more aggressive, but if you really apply the brakes, this bike just stops, and now.)
 
I can't modulate the brake as fast as the ABS system does, and I can't monitor the road surface/sensors like it does, so I'm very, very happy to have it helping to keep me in control of the bike, and not laying on the ground, wondering what happened, and why it suddenly slipped or failed. Same goes for the traction control. It's wild to know you can pretty much nail the throttle, and only pull a short wheelie, while the traction control system modulates the gas for you.
 
Turn it over to A mode, and that's not the case, and you can wheelie as much as you want, but I've found I don't have a problem with the "STD" mode in day to day rides to work where you don't really know exactly what the road is like today, since you have not ridden over it yet. (If I'm going to push, I like to ride a road, then come back and ride it more when you affirm it's safe and clean to push it.)
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If I remember correctly, the owners manual indicates the FJ09 has the rear brake applied when you apply the front brake lever, but then "disengages" the rear/front connection if you use the foot/rear brake during this process. 
So, on every normal front brake use, it also applies some rear brake as determined by the ABS system. (I can confirm this as I never use the rear brake 99.9% of the time, yet my rear brake rotor is showing signs of use that it never has on any other bike I've owned, including the 2014 FZ09 I had prior to this 2015 FJ09.)
I think you are mistaken, or are remembering the owner's manual for a different bike. 
Regarding the wear pattern on the rear, maybe you're accidentally depressing the brake and you don't know it (that's easy to do on some bikes or in some boot/peg positions), or you're just seeing wear from the normal rubbing of the pads and rotor even when the brakes aren't applied.
 
There is no linking front to rear on the FJ; if there were it would have to be happening within the ABS control unit, that's the only place where both front and rear hydraulics meet in any way.  But everything I've read claims they're independent, including the testing protocols.
 
Yamaha does not claim that the brakes are linked in the owner's manual; quite the opposite.  On page 4-19 (of the US spec owner's manual):
 
"The Yamaha ABS (Anti-lock Brake System) features a dual electronic control system, which acts on the front and rear brakes independently."
 
(Emphasis mine.)
 
The manual also explicitly states that the front brake lever controls the front caliper, and the rear brake pedal the rear caliper:
 
"To apply the front brake, pull the lever toward the throttle grip."
"To apply the rear brake, press down on the brake pedal."
 
There's no mention of any cross-control.  The FJ*R* does have linked brakes.  So, if you've read that manual, maybe that's what you recall.
 
Anyway, ABS doesn't apply the brakes, it forces them to release in order to stop a skid in progress.
 
There are automotive systems that use modulators to apply brakes for stability management and/or to pass power through a diff to other wheel(s), but the FJ doesn't do that and I've never heard of any other motorcycle doing that either.  Motorcycle traction control works by one or another type of engine modulation -- inhibit or retard spark, cut fuel injection, cut throttle.   Perhaps some day in the future a motorcycle will apply brakes for stability management, but that's such a tough nut to crack technically that I wouldn't expect it any time soon.  The most sophisticated motorcycle systems on the market now, like the one on the KTM Adventure, use sophisticated monitoring to determine level of ABS intervention in a skid, and to make a good guess as to when they should modulate engine power to avoid overpowering available traction.  It's great stuff, but it doesn't ever apply the brakes automatically.
 
 
2015 FJ-09 (Mary Kate)
2007 Daytona 675 (Tabitha, ret.)
1998 Vulcan 800 (Ret.)
2001 SV650S (Veronica, Ret.)
2000 Intruder 800 (Ret.)
 
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