Disable ABS

[xlxr]

Currently, I am thinking that you cannot disable signal from rear wheel sensor to ECU because that also disconnects speedo and TCS. Assuming front and rear ABS are completely independent, maybe disconnecting the signal from ECU to rear ABS solenoid will work????

[wessie]

With 1,300 miles on my bike, I figured brakes were worn in enough to test rear ABS. On dry pavement at 40 mph I hit the rear brake by itself and measured the stopping distance by referencing cracks in the road and curb. If I just smashed the brake pedal as hard as possible and kept it in ABS mode all the way to full stop, the braking distance was 5 to 10 feet longer than if I tried to hold just enough pressure to NOT initiate ABS mode. The less I let the ABS cycle, the shorter the braking distance. If the ABS cycled only once or twice, the braking distance was still shorter than if I let the ABS cycle continuously. I encourage others to do the same test and post their results. 
Then I unbolted the rear wheel sensor and just zip tied it out of the way. This killed the speed/mph reading on the dash gauge and lighted up the TCS and check engine light, but everything else seemed to work. This completely disabled the rear ABS, and made it much easier to lock up rear tire. I cannot remember for sure, but I think the front ABS still worked, I only tested the front once. Once I bolted the rear wheel sensor back in place, the error lights when out, speedo worked, rear ABS worked, but I have no idea if error codes remained in ECU.
 
I have a service manual and could not find separate fuses for front or rear ABS, but I will need to look in more detail when I have time. It looks like pulling fuses disconnects the entire ABS system. The video at the start of this thread shows how to pull one fuse, so I am not sure why later posts refer to 2 fuses.
 
I still want to disconnect rear ABS, but leave front intact. My main reason is that it is easy to tell if the rear locks up, and I do not need or want rear ABS. With rear ABS disconnected, if ABS kicks in and starts to cycle, I know it is the front brake that needs modulating.
 
 
More experimenting to continue when I have time.
 

 
 
It's all very well doing this on dry roads without the distraction of other road users and pedestrians. Now go and repeat your tests, simulating urban streets in winter where it's raining, you exit a roundabout to find a pedestrian has ignored the red man light, stepped into the road and a truck has just spilled diesel on the road. It's situations like this, that are relatively common for commuters in UK cities, that make ABS a lifesaver for the rider and maybe others. I would also rather the car following had ABS so the driver doesn't lock up and ram me up the arse after I stop.

[eeetea]

Tongue in cheek English humour I'm afraid

Thing is, I'm of English heritage, and I still didn't get it.  I think the paper bag is mine, eh.

Its irony rather than comedy - On one hand I state that everyone agrees that they managed without, then conveniently forget the ones that phucked up at didn't survive, that, had they survived, would have welcomed ABS.
 
"They" also say if thou have to explain it, then it wasn't funny. ...I'll get my coat.
 

[xlxr]

If you want to keep ABS, that is your choice.  I see it as a compromise at best, and definitely not the optimum braking system in all situations.  ABS lengthens braking distance, with the assumption it provides better control.  Did you read the multiple reports from myself and other riders about ABS actually ineffective and dangerous on slippery wash board roads?   I don't consider the ABS system on FJ 09 to be very effective at minimizing breaking distance or very advanced in design to work well in all conditions.
 
If ABS is so great, why do dirt bikers hate it?????? 
 
I am an old dirt biker and it is strange how 35 years of riding/braking skills are now instinct programs burned  into my brain.  Rear ABS screws up those instinctual reactions. Once I get the rear ABS turned off, then I will probably keep front ABS.
 

[jimf]

It's all very well doing this on dry roads without the distraction of other road users and pedestrians. Now go and repeat your tests, simulating urban streets in winter where it's raining, you exit a roundabout to find a pedestrian has ignored the red man light, stepped into the road and a truck has just spilled diesel on the road. It's situations like this, that are relatively common for commuters in UK cities, that make ABS a lifesaver for the rider and maybe others. I would also rather the car following had ABS so the driver doesn't lock up and ram me up the arse after I stop.

Here is the thing: ABS is not magic. It's a recovery system. Those statements that "ABS does worse" ignore the simple fact that if you're braking optimally ABS will not engage. It only does so when you've screwed the pooch and overcome available traction. Moreover, ABS will correct for this faster than you -- or anyone -- can.
 
Human reaction times are rarely much better than 0.3sec at the best of times. With more than one braking channel to contend with, and your attention split between braking and whatever it was that made you have to drop anchor in the first place, it's almost certain to be two or even three times that long. In contrast, even the lousiest ABS systems are significantly faster, and they are that fast every time, no matter what is going on around them or how many wheels they are controlling.
 
To give you a real-world example, the first round of budget ABS systems from GM back in the early 1990s, which were considered laughably bad even at the time, still managed a cycle time of .18sec -- half the time of a human under optimal conditions. Today's systems are at least five times faster than that, typically ten times, and some are more than 20 times faster. I'd have to go dig around to find the FJ's cycle times, but from experience I believe it's cycling no slower than .03sec -- fully an order of magnitude faster than the best you'll be able to manage manually, and likely 20-30x faster in an emergency situation.
 
What's more, it's that fast on both channels simultaneously. You aren't; while your digits can manage to react in a few tenths of a second, your ankle has nowhere near that dexterity. On top of that, human dexterity and reaction times drop off a cliff as soon as attention is split. Reaction times don't halve when you've got two things to contend with, they fall off 80+%. (There is of course a range, but very very few people do much better than that, and only with a lot of training so it becomes reflexive.)
 
This explains why it is, as you point out, extemely difficult to beat ABS systems under non-ideal situations, especially with multiple distractions. Humans are just not very good at that.
 
I'm pretty darn good at modulating the front brake optimally, the result of many hours of mountain bike riding and near-daily emergency braking practice on the bike (a habit I developed after screwing up a few times avoiding morons. The rear, though? Nope. In emergency situations I lock the rear 100% of the time. Pre-ABS the best technique for me was to ignore the rear entirely so the bike would remain stable, and put all of my attention on modulating the front. It made a big real-world difference.
 
Granted, there are people who can do that pretty darn well; you can watch them in slow-mo on every MotoGP broadcast, for instance. But even they are doing it under tightly controlled circumstances, and they screw it up quite a lot as soon as you put moisture on the track -- never mind automobiles.
 
Also granted, the situation on dirt is very different. ABS systems tend to be awful in dirt (and even worse in snow!), where lockups can build a wedge of material ahead of the tire and improve brake performance dramatically. The best ABS systems can adapt to conditions and do very well anyway, but simple systems like in the FJ are quite bad at it. (Then again, so is its suspension, and look at all that vulnerable stuff on the bottom that you can easily destroy with rocks. It's not intended as a dirtbike, no matter that some of us will use it that way anyway.)
 
On the other hand, there is a good reason why a lot of bikes that are intended to be used a lot in dirt offer a mixed-mode ABS where the front wheel uses ABS and the rear does not. Front wheel slides cause crashes frequently and ABS can reduce that likelihood. On the dirt, then, the question is a value judgement between improved braking on the front versus the increased likelihood of crashing. On a lightweight dirtbike the answer may very well be "no ABS." On a $20,000 R1200GS, however....

[xlxr]

Your reaction time analogy is so flawed in logic it is completely meaningless. Rider reaction time is exactly the same with or without ABS. In both cases, nothing happens until you get your foot on the brake. With ABS, the brakes are OFF 25% of the time (I have no idea what the actual number is.) Even if I have to let off the brake pedal 2 or 3 times in a single stop to let the bike straighten out without rear ABS, the time the brakes are on is still way longer than if the ABS is cycling on and off 15 or 20 times. So it really doesn't matter what the road surface is like, ABS extends braking distance.
 
On a motorcycle, the front provides 80% of the braking power. Since I cannot easily tell if front or rear ABS is kicking off, I don't know how much to modulate the front brake, adding even longer braking distance.

[duhs10]

The reaction time is in reference to a human's ability to make adjustments once the tire has lost traction not the initial reaction to hit the brakes.
 
I think that we are missing the point of ABS... it's there as a safety net, not to activate purposelfully. If the rider brakes optimally, the ABS will never kick in thus the bike will stop in the shortest distance possible. If a rider grabs the brakes so much that the brakes are in full ABS mode, then yes the bike will take longer to stop than if the bike was braked optimally without activating ABS. ABS is not there to be activated for the full duration of braking, although it can function that way if the rider input causes it, it is there so that when a rider is braking optimally and then you hit some crosswalk paint or oil on the road, you will not lose control and the bike has the ability to return to optimal braking. 99% of the time if a bike loses traction at the front wheel, the bike is going down.
 
I agree that ABS is not as important for the rear as it is for the front. However, I think that an ABS equipped bike will stop shorter and safer than a non ABS bike simply because it allows the rider to brake optimally only activating once the rider has exceeded available traction.

[jimf]

Your reaction time analogy is so flawed in logic it is completely meaningless. Rider reaction time is exactly the same with or without ABS.

 
Err, you have misinterpreted what I was trying to get at. I was comparing the time to correct a skid caused by overbraking between human and ABS, not time to initiate braking in the first place. The latter is a very interesting topic these days, though, which I'll get to a bit later.
 
The best way to utilize an ABS system is to keep just under the point where it engages; this is very, very close to the optimal braking force relative to available traction. If you can do that consistently, regardless of conditions or distractions, then ABS won't be especially helpful. Unfortunately, in the real world, nobody is that good all the time and very few are that good in anything but ideal conditions.
 

With ABS, the brakes are OFF 25% of the time (I have no idea what the actual number is.) Even if I have to let off the brake pedal 2 or 3 times in a single stop to let the bike straighten out without rear ABS, the time the brakes are on is still way longer than if the ABS is cycling on and off 15 or 20 times. So it really doesn't matter what the road surface is like, ABS extends braking distance.

 
You have made a very large omission in this analysis: You assume that "brakes on" is the same in both cases, and it isn't.
 
Once you're skidding you lose a huge fraction of available braking force; it's the difference between sliding and static friction, and the difference is huge. So, all that time you're taking to reduce pressure and recover from the skid is spent with the brakes operating at a small fraction -- typically well under half -- of the available braking force if you weren't skidding.
 
By cycling rapidly the ABS is going in and out of the skid point, spending some of its time not skidding, whereas you spend none of your time not skidding. An ABS system would have to have the brakes completely disengaged more than half of the time to do worse than you are, and that just isn't what happens.
 
Let's take some example numbers to illustrate. We know that sliding friction is less than half of static; let's just say it's (a very generous) 50%. If ABS were spending half of its time without the brakes applied then it couldn't do any better than 25% of optimum (half of the time braking at half of available force). If it were spending all of its time sliding, it would do no better than 50%, the difference between sliding and static friction.
 
In the real world, however, ABS systems typically brake at 90% of optimum or better. (Many magazines supply both figures for motorcycles so you can see that this is true.) That would simply not be possible unless the ABS system were spending the majority of its time not only not skidding, but also running very close to the optimum braking force.
 
ABS systems do not work by watching for a skid and just fully releasing the brakes for awhile. They watch for a skid, reduce braking until the skid stops, and then reapply until the skid starts again. The faster you can run that cycle, and the less you have to reduce pressure to get the wheel rolling again, the closer to the best possible braking you'll get -- crossing over and under the skid point, but never by very far.
 
Anyway, the thing to remember is the flip-side of the "they operate 10% worse than optimal" number: Even if you have completely screwed up your braking, an ABS system will allow you to get 90% of the performance out of the brakes anyway. If you do not have ABS that number drops below 50%, and only that good if you keep the bike upright and don't just let go of the brakes in a panic when the front starts sliding, which is one of the two things almost everyone does the first few times they're confronted with a front-wheel skid (the other is that they crash, or in the common vernacular, "lay it down").
 
Which brings me to another point, one of the ease of determining maximum braking force.
 
Without ABS the right way to brake is to ease the brakes on, initiating weight transfer and gradually increasing braking force until the wheel is just starting to cry a little. Alas, that is a pretty damn hard thing to do when you're staring at the front quarter panel of the asshat who just turned left in front of you. It is common -- very, very common -- to jam on the brakes and just plain fall down, even when there would have been plenty of space to stop. This is the whole point of the MSF emergency braking drill, to teach you how to brake hard and fast, but not too fast.
 
ABS, however, gives you another option, and one that works very well even in the most panic-strewn situation: Grab all the brakes you can, engaging the ABS, and then reduce brake force until it stops cycling. The ABS will immediately be giving you 90% of optimum, and once you drop below the cycle point you will be at or very, very near the optimum. Most importantly this works well given the reflexive reaction is to grab too much brake anyway, with your mind taking a second or so to catch up and remind you that modulation would be a good idea.
 
Also, very few people are any good at modulating the rear brake. I mentioned before that I locked mine 100% of the time in panic situations, causing loss of stability and risk of highside. Recognizing that I was unable to properly modulate the rear I trained myself not to use the rear at all in such situations, and the end result was far more control when things went pear-shaped.
 
ABS changes the equation on that, too; it's entirely reasonable to smash down on the rear because the ABS system will control the skid for you. No loss of control, and again you get about 90% of maximum available braking force. That's a whole lot better than the 0% I was getting with my "no rear brakes" technique, right? Now, that's not actually a big improvement in the real world because even a cruiser only gets a maximum of 25% of braking from the rear; most bikes get perhaps 10%, and sportbikes more like 5%. Even so, that paltry 4% could be the difference between stopping in time and an ambulance ride. I'll take it, TYVM.
 

On a motorcycle, the front provides 80% of the braking power. Since I cannot easily tell if front or rear ABS is kicking off, I don't know how much to modulate the front brake, adding even longer braking distance.

 
The 80% number is a rule of thumb across most vehicles, but as I just mentioned the number can be much higher for some motorcycle types -- it depends a lot on where the center of gravity is. The higher and more forward it is, the more you get from the front.
 
Regarding "can't easily tell if front or rear ABS is kicking off," that is something you can learn to differentiate with a little practice. It's not hard at all to tell the difference between pulsing in your fingertips and pulsing in your boot once you get to the point where your brain is interpreting rather than panicking.
 
With or without ABS the best way to get good at this stuff is to practice, practice, practice. I do so almost every ride, rain or shine. I'm not ashamed to say that I was completely terrible at it when I first started riding, so much so that I would routinely get waaaay close to hitting someone who pulled out in front of me even though I should have been able to come to a complete stop before I was halfway there -- this despite MSF training. With regular practice I got much, much better.
 
The FJ is the first bike I've ever owned with ABS, and I'm also not ashamed to say that when I first started practicing with it I also had a hard time determining which end was pulsing. The more times I activated ABS the better I got at being able to figure that out. Also, the better I got at being able to determine the line at which ABS would engage. Pre-ABS that was kind of scary to push the brakes to the max since a locked front can easily put you on the floor and cost hundreds or even thousands to repair the bike.
 
The technique I worked out is very simple: Give the rear a nice big push and let the ABS system sort that out, ignoring whatever I'm feeling in my boot. At the same time, try my best to ease the brakes on to get the weight transfer going, but if ABS starts cycling I'll feel it in my fingers and reduce pressure a little bit until cycling stops. Because I do this again and again using the same strip of tarmac and braking/stop points, I have been able to objectively determine that this technique has allowed me to become far more consistent at it than I ever was without ABS.
 
Time for a sidebar I mentioned before, on the difference between human and computer initiating braking. About five years ago now the insurance figures started to come in on the first Volvo model that included an automatic braking system. The numbers were startling: The automatic braking system reduced the overall accident rate by more than 80% versus Volvos that did not have that feature.
 
Going back to the early 1990s, the theory was that pushing ABS as a standard safety feature was going to reduce accident rates a lot. As the numbers came back from accident statistics it turned out that they had no effect at all. The theory most commonly espoused as to why this was the case was "risk compensation," the idea that having additional safety features makes you feel that you can expose yourself to greater risk because you are "protected." While it's likely that this is the case for the more extreme amongst us, speaking with a number of "normal" people I found that few people had any idea what ABS did, and many didn't even know their car had the feature at all.
 
I drew a different conclusion: I believed that the problem wasn't that the car's braking system was not performing as well as it could, but rather that most drivers involved in accidents weren't applying their brakes anywhere near soon enough. By the time they realized they ought to be braking hard the braking system was not going to be adequate no matter what, so ABS or no ABS didn't matter.
 
Those Volvo statistics vindicate my point of view. When the computer figures out that you're in trouble and initiates emergency braking for you, accident rates drop by a huge percentage. Moreover, those ABS systems proved more than adequate to get the vehicle stopped a gigantic fraction of the time. Braking early is way more important than getting that last 10 or 20% out of your braking system. The lesson for us motorcyclists? Look as far ahead as you can to see the danger points. The faster you see them the faster you're on your brakes and the more likely you don't hit something.

[eeetea]

The point for me at least is, Emergency breaking is extremely rare I can't even remember the last time I hit the breaks hard...yes... once in Wales 3 years ago.
 
But I have, several times a year, every year and even a few times on the same journey wanted to purposely lock the wheel (only for a split second to cut in) to get through top dressing and debris to hit the tarmac underneath. ABS stops me having that option and consequently stops me stopping.
 
All the research arguments for ABS is based on tarmac, and assumes for public highways that are not loose. Unfortunately the truth is, it often is, back country roads, wah out after heavy rains, top dressing with an inch of loose chippings are all real frequently encountered realities.
 
 

[xlxr]

JEEESSSS, I just want to find out how to disconnect rear ABS. I do not like it, and I do not want it. I never ride in the rain or dirt, so I am not concerned about those conditions. Using back brake only, on dry paved road, in a straight line, I can stop shorter without ABS. I'm waiting to hear from some one who has done the same test.

[xlxr]

I read up on ABS in Yamaha service manual. There does not appear to be any way to disconnect rear ABS only from electrical circuit. Apparently, the ECU does store error codes caused by disconnecting the rear wheel sensor and some special gizmo from Yamaha is needed to clear error codes.

[xlxr]

OOOPPPSS, I suddenly realized a basic flaw in my own reasoning. In hard straight line braking on dry pavement with the front brake, the bike pitches forward so much that there is almost no weight on the rear wheel. Therefor, the extended braking distance caused by rear ABS probably gets close to insignificant because the rear tire can't do much braking anyway. So, like the previous posters said, time for more practice.

[jrkman]

I feel like people are comparing stopping distance with abs engaged, to stopping distance with perfect brake control. The real test is stopping distance when abs engages and then comparing that with stopping distance for the "same" brake pressure with no abs. This would mean skidding. See what one is shorter and safer.

[eeetea]

Or where you need to lock to cut through surface debris which is shorter.
 
I agree panic braking, for all but highly tuned motoGP riders and their ilk, ABS will win.
 
But I haven't had to panic brake in donkeys years..once..but need to lock many times a year to cut through surface dressing clippings and the like.

[xlxr]

In my simple test, ABS on rear only increased stopping distance by 5 to 10 feet from 40 mph on dry paved road in a straight line.  Pretty much proves  under those conditions, ABS on rear takes longer to stop.   I will also submit, if you cannot control rear wheel skid without ABS, your riding skills are not adequate and you need ABS.
 
No more theory and assumptions.  I want to hear from guys who have actually tried my test, to see if they get the same results.