"ABS" has been misnamed from day one

[ANDYVH]

There have been numerous articles on the effectiveness of ABS systems on cycles, to help the rider maintain control when braking in a straight line. But, I have never seen an article or video, relative to the limited capabilities of ABS on a cycle when the bike is leaned into a turn, or when swerving. But, many videos of ABS stops of cars also show the car being "steered" around an obstacle as part of the capabilites of the system. When a bike is leaned into a turn, lots of traction is being used. Current ABS systems only function once a wheel is braked, and that braked wheel must already be slightly past the traction thresehold (about 10% to 20). Most all of us know that combination is NOT good when leaned into a turn. Yet I bet many riders assume the ABS on their cycle will cover their butt if they loose control in a turn while braking, just like with the ABS in their car.

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,. That combination is not a function of "stable" riding for most of us.

[lkchris]

Comparisons to cars are apples/oranges of course and not very relevant.

"Losing control" in a curve with a motorcycle essentially means you've fallen down and it's obvious brakes don't prevent that. But, if you're not quite to that point and slowing down can help, ABS is good and brake locking isn't.

Moving on ... with cars, the ABS functions can be turned around to prevent wheel spin, making limited slip differentials a bit old fashioned for example. And on cars traction control systems tied to the brakes can essentially detect when the car is not tracking straight and can even control trailer sway. Also all obviously not relevant to bikes.

More interesting, perhaps, are the traction control systems--called ASC on BMW motorcycles (automatic stability control)--where the electronic sensors talk to engine control rather than a brake fluid pump and prevent loss of traction due to the engine overpowering the rear tire's ability to cope. This CAN without question help you on a motorcycle in a curve.

[oldnslow]

Am I missing something here?

Antilock Brake System. A system that prevents the brakes from locking up. Doesn't imply stability control to me. :scratch Although, if my front wheel is not skidding in a panic stop, I will have control. :scratch

[rdalland]

from the MOA facebook page...

https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-snc7/377260_2740303477101_1542858299_32765769_122295000 8_n.jpg

[Fourcats]

:laugh THAT is funny!

[ANDYVH]

Mike, to your comment, "Antilock Brake System. A system that prevents the brakes from locking up. Doesn't imply stability control to me." If a braked wheel skids, and the bike looses balance and dumps, that is a loss of stability. If the rider applies too much throttle in a turn, and the rear wheel slides out and the bike dumps, that is a loss of stability. So both ABS and Traction Control are really stability assist systems. A bike is only stable when moving if the rider has control. Or if the bike is stationary and parked on the sidestand or centerstand. So, maybe I need to clarify this a bit further:

Yes, ABS is a system to keep the brake from locking up. BUT, the key factor is that to "initiate" ABS control on a wheel/brake, two things have to happen together:
1. The brake must be applied on that wheel. So the rider must first apply brake pressure. With no brake pressure applied to the wheel, the ABS is doing nothing but monitoring wheel speed.
2. The wheel HAS to slightly break traction, slip, skid, to get ABS control to start. ABS control logic is based on the wheel jexceeding traction by a preset amount before ABS control even starts.

It is that initial "break traction" aspect of ABS control that is the problem for bikes when they are leaned over into a turn. In a straight line, if the tire skids for a fraction of a second, the bike can still be controlled. But in a turn, or leaned over, even that fraction of a second "may" be enough to loose stability. Or perhaps the bike doesn't fall over in that brief moment. But then if it suddenly gains traction when leaned over, the results can be violent enough to throw the rider off the bike. That is why I would like to see tests of an ABS equipped bike (with outriggers), brakes over applied in a curve, to see how the bike and ABS system reacts. I may be wrong about the results, but if so I'd like to see that proven.

Also, every ABS engineer I have talked to all refer to ABS systems as stability control systems and not as braking systems. They assist stability control by using the brakes.

Mike, based on your response I'm curious: do you feel that onn a bike with ABS that you could apply all the brakes you want in a turn while leaned over, and expect the ABS to not let a wheel lock up? Because in that expectation you would assume you'd not loose control?

Ikchris, your comment puzzles me, "But, if you're not quite to that point and slowing down can help, ABS is good and brake locking isn't." Because your comment says what I think a lot of people expect of ABS systems: that being an expectation that ABS helps in all braking conditions. Well, ABS ONLY helps when the braked tire HAS LOST TRACTION. Until that happens, ABS does nothing to help the rider. Until traction is lost on the wheel being braked, it is NO different than on a bike without ABS. That is the problem of perception of what ABS systems do.

Now don't think I am bad-mouthing ABS systems, or that I feel I can out-perform any ABS system because of my "expert skill level" because neither is the case. I have owned an ABS equipped bike for 17 years, and even repaired the ABS system after it failed to make sure it would still help me when needed. But, we have to be aware of what ABS systems can and cannot do.

[RoboRider]

I see your point, but obviously you shouldn't be braking in a corner anyway (other than some trail braking). Most problems in a corner, which is the fear of running wide due to too much entry speed, can be solved by leaning much harder. Very few riders ever lean as much as the bike can lean, thus low-siding. You see it all the time, a better rider could have made the turn. And if you do decide to brake, MSF teaches you to straighten up first. So better training would help.

But, that's not your point. Your point (I think) is that ABS applied in a hard lean corner will still likely result in a crash. I agree. But still, I'll take ABS over no ABS. I have had it kick in on a slick road and other times, and it is very nice to have. But it's not a panacea.

This guy could have benefited from ABS:

http://youtu.be/8PE9cozFuAw

Note how he was not leaned over much at all. In the slow mo, you can see a nice front wheel skid lay down a line of rubber on the road before he goes down. I think ABS would have saved him this crash. Not relevant to this discussion, but that guard rail saved his butt, too, from a long ride down a cliff.

[pffog]

Well not scientific, but in 50k+ miles one of the only times my ABS was not activated on purpose, was leaned WAY over at a track day at Summit Point Shenandoah circuit.

A quick transition from hard left to hard right at the crest of a hill found another rider blowing his line and heading across my path, just a few feet ahead. I stabbed the brakes, and felt the bars go loose for just a split second, before the abs kicked in, and the front tire regained traction, I of course let off too, but the electrons travel through the bikes system faster than they do mine.

Yes sudden regaining traction in a slide can cause a high side, but IMHO ABS cycles fast enough to prevent lateral momentum to build, provided there is enough traction to reconnect.

This is the ONLY time I feel the ABS saved my bacon, and it was on a RACE track. OK purists, have at it. IMHO ABS can save you more that hurt you, any day.

Besides I can get near maximum braking force NOW, not after I gently squeeze the lever to settle the chassis then adjust the lever pressure to provide threshold force, which for 99.999% of humans is IMPOSSIBLE.

People that claim practice is as good as ABS, I say bull. Look at ANY professional racing form, car of bike, and you will see the BEST humans at their trade, that get paid millions to do nothing BUT practice, lock up their brakes by mistake. Yes dumb luck might have saved you once, but luck is hard to consistently repeat.

[RoboRider]

IMHO ABS can save you more that hurt you, any day.

Besides I can get near maximum braking force NOW, not after I gently squeeze the lever to settle the chassis then adjust the lever pressure to provide threshold force, which for 99.999% of humans is IMPOSSIBLE.

People that claim practice is as good as ABS, I say bull. Look at ANY professional racing form, car of bike, and you will see the BEST humans at their trade, that get paid millions to do nothing BUT practice, lock up their brakes by mistake. Yes dumb luck might have saved you once, but luck is hard to consistently repeat.

Those 3 statements: ABS is better than no ABS, ABS is better than the average Joe at maximum braking, and even pros make mistakes.

Those 3 statements really hit home. Sure, I'm all for BETTER ABS, but Andy, is your point ABS is a waste of time or ABS should just be better?

[ANDYVH]

To this question, "but Andy, is your point ABS is a waste of time or ABS should just be better?"

Actually my point is ABS is neither a waste of time (or money), nor should ABS be better. My point has always been to be sure we riders really understand what ABS does, is capable of, and not capable of. I really think a lot of riders have the impression that ABS will always cover thier transgression. Well, ABS "might", but I for one am not willing to depend on it that way. But I would like to see actual test data and video to support my feelings. If I am proved wrong, GREAT! If I am proved right, then no big whoppie on my part, just an understanding would be available to those wanting to know more.

Years ago I had opportunity to work directly with Bosch ABS engineers at their winter test sites in Baudette MN and in Areplog, Sweden (60 miles from the artic circle). I learned an awful lot about ABS control and principles, enough so that Bosch offerred me a job as a heavy truck ABS engineer (just before the truck market went seriously down, good thing I didn't take the offer).

I too am an MSF instructor of 20 years, so the control principles are firmly ingrained in the cranium. I also support always using proper technique rather than depending on some support system to save your butt. Good braking skills and cornering skills have FAR higher priority than any ABS system. I looked at that video of the Duc rider lowsiding into the guard rail. For where his front tire locked (note also that his front tire is turned LEFT right as it starts skidding), and that his bike was largely upright, I agree that ABS "could" have helped him avoid the tire skid and lowside. BUT, with that, even far worse could have happened. Again look close at the video and you'll see his front tire turned left, which may be the result of him locking the front wheel. But I suspect, for all his glorious riding gear and beautiful Duc sportbike, that he had a perceptual problem with quick and accurate leaning/turning capability. Hard to say if he TURNED the handlebar left and then clamped on the brake, or if he clamped on the brake and as a result of it locking he turned left on the handlebar. Regardless really, because had ABS helped him regain traction at that instant, and had he kept the wheel turned left, he would have gone quick HARD right, the result of a hard left countersteer! Right into the guard rail. To correct for his initial mistake, after regaining traction, he would then have to press even HARDER LEFT to maintain control and avoid running wide. My bet, ABS or not, this guy was gonna crash. That he lowsided in this instance, I feel, was the BETTER of having ABS help out his ham-fisted over-braking technique. Of course, that's easy to say from behind my laptop. But that his front wheel is turned the wrong way in an area with NO runoff, he's better off he didn't have ABS in my opinion.

The Duk rider made a decent entry position choice, but then messed up after that. Perhaps freaking out looking at the guard rail and precipice beyond, and then freaked out clamping on the front brake, which he clearly did before attempting quick increased lean-in. For his speed and ground clearance, all he had to do was maintain throttle and press hard on the LEFT handgrip to lean the bike in quickly. He would likely have cleared the turn with NO braking at all. Too bad we don't get to see the broader view of this lowside, to see if oncoming traffic forced his decision. But this particular turn on the MulHolland canyon road gets a LOT of youtube lowside videos. These kinds of youtube videos can be good learning tools, but there is a LOT you have to look at and consider to determine if something like ABS would have saved him. However, again, the perception is that ABS would have saved him, and others might agree thinking it would help them. My gut says in this case it may have been far worse. Far too many variables about ABS control and leaning/turning than we can make here. But always, GOOD BASIC riding skills do make a huge difference all the time.

[RoboRider]

Ah, I see. I think we pretty much agree on this.

The Duc rider really did take a corner that was easily makable, and for some reason reacted poorly and dumped it. His skills do not match up with his leather track suit!

So I agree, TRAINING is #1. Track Day training is to me, a must. If you take corners dragging a knee on the track, you will rarely find you take a corner "too hot" on the street.

ABS is great to have, and might save a dump, but skill is and always should be #1.

[ANDYVH]

In your earlier response, you said you weren't sure if the video was relavent to the discussion. I think it was spot on! This is some canyon racer, on a public highway, in MUCH better riding gear than most of us wear, making a mistake and paying for it. Either his lack of skills, or his poor choice of the skills he had, or that he simply freaked out (my guess) cost him a lot.

But again, IN THIS INSTANCE, I feel ABS "may" have resulted in a worse outcome. Yet, how may people look at that video and respond likewise, "I feel ABS would have saved him from this crash." What if that rider sued Ducati because they didn't offer ABS on that bike? In court, to an unknowing jury and lawyers, he might get a huge settlement. But with some real study of the video (one of the benefits of this video age), a defense lawyer for Ducati would have closed this one down quick.

[RoboRider]

I meant the comment on the guard rail was not relevant!

Why do you think ABS might have made it worse?

[ANDYVH]

I felt that ABS "could" have made this worse for the following reasons, and again this is based on the conditions we see on the video, and on the premise that the rider, cycle and conditions are all the same:
1. Look at the conditions preceding the lowside, the front tire is turned to the left.
2. The bike, once the tire is locked is sliding to the outside of the turn. That's just physics. Once lateral traction is gone, the bike will always slide to the outside of a turn.
3. Even though the wheel is turned left, at the intiation of the skid, the bike is largely upright. But the front wheel is turned pretty significantly left. That means if traction is suddenly gained, everything above the rotational axis of the bike would have wanted to go to the right, toward the guard rail (high side).
4. Very marginal to no run-off room. A narrow shoulder, then guard rail, then Wiley Coyote air time.

Given those conditions, if after initiating the skid, if the front tire would suddenly gain traction I guess some things could happen:
1. The bike will quickly track RIGHT, not left, due to the aggressive countersteer reaction when the front tire gains traction. If the tire were pointed more straight ahead when lockup initiated, then its simply a straight line stop when the ABS engages and the rider "may" be able to quickly press HARD left grip to redirect the bike into the turn.
2. But that is IF the rider is quick, skilled, and practiced at QUICK HARD COUNTERSTEERING. This relates to the very little margin for error with no run-off room. The fact that the rider made the massive error of clamping on the front brake instead of pressing into the turn leads me to think he froze up/freaked out, or simply does not have the skills.
3. So my guess is based on the errors shown, he would not likely have the recovery skills within the very limited space he had to maintain control once traction was gained again.
4. Given the momentum of the bike at that point, and no run-off room, without a HARD LEFT countersteer, the bike would have quickly run right into the guard rail.

That could have pitched the rider over the guard rail instead of low-siding into it. Hmm, now that I think about it, once he lost traction and began to fall, its a good thing he DIDNT let off the brake before the bike went down. If he had, the bike could have highsided him over the guard rail.

[lkchris]

Also, every ABS engineer I have talked to all refer to ABS systems as stability control systems and not as braking systems. They assist stability control by using the brakes.

And that's tangentially true for cars, although not with the earliest ABS systems.

Today, using ABS sensors and more sophisticated pumps and plumbing, an individual brake can be activated to maintain stability. It's not necessarily "pumped" either. The parts in common are the wheel speed sensors; ABS will pump brakes if it determines loss of traction; ECS (electronic stability control) will apply individual brakes to maintain straight-line running (steering angle is checked, too).

It's not really accurate to equate ABS and ESC, but for sure the same wheel speed sensors are utilized and brakes are indeed activated without driver input. There are now systems involving radars that will prevent rear-ending someone and they use servo control of brakes, too, but again these systems are not accurately called ABS either.

And, it's completely irrelevant to motorcycles, where the only goal is to address wheel lockup. BMW ASC addresses wheel spin by cutting engine power, which can certainly be considered a form of stability control, but brakes aren't involved at all.

[ANDYVH]

Correct, my comment about ABS as a stability control applies to stability during braking. My experience with heavy truck traction control systems DID use the brakes to assist traction control like a Posi-Traction system. If a wheel spun up during acceleration, the ABS system applied the brake on the spinning wheel thus sending the torque to the wheel with traction, independent of the driver input.

Early car traction control systems worked on a similar basis. Later iterations developed more to controlling engine power for traction control. Though, in some cases it can be self defeating in deeper snow and sand, because the system does not allow sufficient wheelspin to gain and build any momentum. This I know from first hand experience in winter driving. Many times in heavy snows at slow speeds I am better off to turn the traction control off entirely.

But on a cycle, traction control is done with the engine to limit wheelspin. Which is more logical because there is only one driven wheel.

[barryg]

ABS I allways thought it stood for A Butt Savior. Saved me more than once. :laugh

[Greenwald]

ABS I allways thought it stood for A Butt Savior. Saved me more than once. :laugh

+ 1 !

For the final 5 years that I spent 8 hours a day patrolling on my LEO H-D RoadKing with ABS (non-ABS the first 2 years), I used the system so many times, I lost track. Too easy to get 'lost in the moment' of a pursuit or Code 3 run and get in over your head before you realize it (me bad).

Like you, saved my butt more than once.

But you got to know Andy - when he someday goes to Heaven, CRAY Computers has first dibs on his brain - they will make a super-computer out of it!

He could analyze how a toothpick is formed and make it sound both interesting and still delightfully complex! :bow

[ANDYVH]

Whoa partner! I appreciate the accolades, but I ain't no Einstein by a long shot!!

I'm just wired like your typical engineer type, that likes to think things out to the n'th degree. However, I do have some strongly formed opnions about how cycles function in the realms of physics and logic, and I try to fully understand the dynamics of bikes rather than rely on comments like "ABS will save my butt." Perhaps if I had a cool physics teacher back in high school that rode a cycle and could equate physics to it and me, I woulda aced physics and science easily. Got by ok on a B, but I could have done much better.

[racer7]

The only comparison I'd make between car and bike systems is that the bike systems are primitive and annoying by comparison and linked ABS makes them even more annoying to me, There are some very impressive car electronics out there today- the first time I played with a GTR on track I was amazed at how competent that system was and how little it interferred with seriously hard use. OTOH, I'm not very impressed with electronics as a sub for proper diffs in the more extreme of 4WD situations like deep mud or snow- the Mercedes systems come to mind as a not very good implementation. The current BMW car brake system is pretty decent though a lot of the other electronic stuff like the tranny shift programming and overly intrusive "stability" controls really suck if you actually know how to use a car though they're good for extending tire life.

I still prefer the older style brake systems like that on a K1200RS I ride to the newer one such as on my R1200, for example.

Be interesting to see what happens to bike systems when they start closing the current large gap on cars though I suspect they'll always be 5-10 yrs behind due to economics. Faster cycle times, faster recovery and much better feel are the most badly neded changes, IMO. Some of the problems are caused by the physics of regaining traction on a sliding bike tire- that's a bit of a tough one for the engineers compared to a car

[Greenwald]

Whoa partner! I appreciate the accolades, but I ain't no Einstein by a long shot!!

I'm just wired like your typical engineer type, that likes to think things out to the n'th degree. However, I do have some strongly formed opnions about how cycles function in the realms of physics and logic, and I try fully understand the dynamics of bikes rather than rely on comments like "ABS will save my butt." Perhaps if I had a cool physics teacher back in high school that rode a cycle and could equate physics to it and me, I woulda aced physics and science easily. Got by ok on a B, but I could have done much better.

Reminds me of Einstein's humility, when while being goaded by a reporter as to how it feels to be the world's smartest human, he simply replied "Son, we're all ignorant...............just about different things."

[Motor31]

Equipment can only do so much to make up for the lack of rider skills. If a rider requires the same "stability" from their motorcycle that they get from a cage they do not belong on a motorcycle. Neither vehicle requires the same set of skills from the operator and neither vehicle will respond to inputs in the same manner.

As to the semantics of "anti lock brake system" vs "stability system" it's a bit of a misconception that brakes that do not lock on severe application do NOT provide additional stability over a non ABS equipped vehicle. Hence the term stability assistance still applies.

[barryg]

I apologise for the inapropiate ABS comment. I was just adding a little humour to the serious discussion of the workings of the abs braking system.

[ANDYVH]

Oh, I dunno,....I thought it was totally appropriate. No apology needed.

I'm a Monty Python kind of guy, when the seriousness gets too much, its time for irreverant humor. Humor is good because quite often it exposes the true feelings.

Sure, many may not agree with ABS as a braking or stability system, my intent is to get riders to think beyond either system covering for a rider's mistakes, or worse, a rider's lack of skills. No matter the system or technology, it ALWAYS comes back to the rider. The rider always has to have the skill sets to ride. If a rider does not want to develop those skills, then I have to say that person should not be riding, stick to cars then.

[AKsuited]

Perhaps if I had a cool physics teacher back in high school that rode a cycle and could equate physics to it and me, I woulda aced physics and science easily.

I did have a cool physics teacher in high school, Mr. Walters. I don't think he rode a motorcycle.

But this reminds me of something important I did learn in school, that the static coefficient of friction is usually higher than the sliding coefficient of friction. I still remember the example: push on a heavily loaded cardboard box. You will push harder and harder until it breaks loose and slides. The force required to slide it is less than the force you exerted just before it broke loose. The coefficient of sliding friction is lower.

This is why drag racers lose when they smoke their tires. They can't win a drag race using sliding coefficient of friction because it is lower.

So many people fail to understand that. To stop in the shortest distance, you must use static coefficient of friction, not sliding coefficient. Same thing with measuring skid marks at an accident scene: somewhat informative in the sense that brakes were applied, but is misses the point: the driver would have stopped shorter by not leaving skid marks. And this is where ABS comes in: it keeps you in static coefficient of friction territory and avoids sliding coefficient of friction.

Back to leaned over bikes: you need an ABS system between your ears that knows that motorcycle tires have a limited amount of static friction available and that most of it is used up being leaned over. Jacking your brakes will quickly overwhelm that limit, put you in sliding coefficient of friction territory, and at a minimum have your rear wheel step out or worse case, have you go down hard. Since the forces used to get you around the curve are sideways, the ABS system on the bike can't possibly know about them, and can't help you avoid sliding out.

Harry

[Anyname]

This is why drag racers lose when they smoke their tires. They can't win a drag race using sliding coefficient of friction because it is lower.

Hmmm, most dragsters light them up for quite some distance. It may be that they are just using their tires and the road surface to augment their clutches, but they definitely spin their wheels.

I have had people knowledgeable in physics explain tire to road traction in terms of basic physics, and it always seems to imply that traction is determined by the load on the wheel. Also that the surface area of the tire on the road isn't important. Based on actual observations of vehicles, I have to conclude that the basic physics are only part of the equation, and that rubber compounds, tire construction, tire geometry (tall and narrow vs low and wide), temperature, the road surface (both large and small irregularities), vehicle suspension and a host of other things have a large effect on traction as you experience it on a vehicle.

[ANDYVH]

Yeah, I agree. Tire traction is a black art in itself, many more variables than just tire load and surface are of contact.

I also understand the reply about static and sliding friction, and I think I understand your point. Though I can't quite agree on the aspect of static versus sliding friction. Static friction has much to do with the "breakaway force" to get a stationary body in motion. Consider a heavy metal block on a table top. It takes more force to get it moving, than it does to keep it moving.

Since a motorcycle in motion is the main realm of ABS system, it is more sliding motion even if the tire does stop rotating. The mass of bike and rider in motion, in contact at the road on the tire contact patches, I think is still sliding friction versus static friction. Most ABS systems require a 10% to 20% slip thresehold to be exceeded for ABS control to engage, which is the tire already sliding slightly while the bike is in motion.

Interesting discussion though, far deeper than reviewing what latest piece of shiny chrome bling some riders focus their discussions on. Chrome don't get you home!

[AKsuited]

Since a motorcycle in motion is the main realm of ABS system, it is more sliding motion even if the tire does stop rotating.

As soon as the tire stops rotating, it is all sliding motion, and sliding coefficient of friction. That's basically all an ABS system does: check to see if the wheel is still rotating. If it isn't, then by definition the tire is sliding.

The mass of bike and rider in motion, in contact at the road on the tire contact patches, I think is still sliding friction versus static friction. I have to disagree. As long as the tire is not sliding, it is static coefficient of friction. Most ABS systems require a 10% to 20% slip thresehold to be exceeded for ABS control to engage, which is the tire already sliding slightly while the bike is in motion. I don't know enough about the details of ABS systems other than to point out as above that the whole purpose of ABS is to detect a non-rotating wheel, and cutting off braking force to the wheels when that happens.

Harry

[Rollifahrer]

It seems much of the thread relates to hard braking in corners. I think we'e asking too much of mechanical systems when we expect them to defy certain laws of physics.


In my limited experience, I've discovered that ABS does a good job of preventing wheels from locking up while braking hard IN A STRAIGHT LINE.

In all of my reading and training, most braking should occur before entering a corner, while the bike is vertical and traveling IN A STRAIGHT LINE.

If one misjudges entry speed and needs to apply more brake force prior to the turn in point, ABS intervenes in the event the rider panics and applies to much force to the lever and/or is not skilled at predicting maximum braking without locking up.

Used as intended ABS in fact does prevent wheels from locking, and the OP's claim that a wheel must lock in order to enable ABS functions is not correct. The control unit reads sensor data at a rate of 4 - 8 milliseconds and pulses the valves at 16 times per second. The control unit measures wheel speed and engages when a wheel BEGINS to slow, but before it locks--hence Anti Lock Braking.

The following uses automotive 4-wheel ABS as an example, but the principles apply to all ABS.

Use (Wiki)

There are many different variations and control algorithms for use in an ABS. One of the simpler systems works as follows:[15]
The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 60 mph (96.6 km/h) under ideal conditions, but a wheel that locks up could stop spinning in less than a second.
The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power.
When the ABS system is in operation the driver will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. This pulsing also tells the driver that the ABS has been triggered. Some ABS systems can cycle up to 16 times per second.

[ANDYVH]

Used as intended ABS in fact does prevent wheels from locking, and the OP's claim that a wheel must lock in order to enable ABS functions is not correct.
I am not saying the wheel must "lock", but I am saying the wheel MUST exceed a slower speed preset thresehold before ABS control engages. In many cases, that means the braked tire IS slightly slipping, not locked. BUT! The point is I don't want to rely on a slightly slipping tire which is exceeding traction limits.

The control unit reads sensor data at a rate of 4 - 8 milliseconds and pulses the valves at 16 times per second. The control unit measures wheel speed and engages when a wheel BEGINS to slow, but before it locks--hence Anti Lock Braking.
True, I am not argueing that point. It engages control BEFORE the wheel locks but AFTER the braked wheel IS spinning slower than the other wheel and the actual vehicle speed. It is at THAT point, if leaned over, that I believe ABS stability cannot be fully relied upon. If you are already near the traction limit, then ABS slightly exceeds the traction limit as control is engaged.

I have said it before, and I have not yet read or found anything to disprove it: that ABS systems function on the preset condition of a wheel, with braking applied, slipping at a rotational speed up to 20% less than the actual vehicle speed.

I would really like to find out the actual control parameters typical of motorcycle ABS systems to be disproved on this. But really, my intent on this post is to get riders thinking beyond the realm of "ABS will save my butt if I mess up, even if I do it in a corner." Not true, to me, until proven otherwise.

[BCKRIDER]

1. Isn't the MAIN PROBLEM with both car and bike ABS the fact that so few users "test it" until faced with a real event? When I got my first car with ABS in 1991, I made myself try slamming on the brakes on snowy roads, starting very slowly and always making sure there were no following vehicles. The impulse, ingrained from years of driving cars which lacked this feature, of releasing the brake when you heard and felt the ABS activating was VERY STRONG. I still do this drill every year after the first snowfall - and I know I am negligent for not practicing the same thing in the rain. And maybe also on dry pavement.

I only once got to "practice" steering with the ABS activated - and am still amazed that I remembered this piece of information when I really needed it. But I steered my way around a couple of stalled vehicles while descending a very slippery road. Would have had a fender bender, without question, without ABS.

I wish I had conducted the same tests on my current bike - when the ABS actually worked. Well, I sort of did with the rear brake on gravel. Seems to me the rear brake produced a number of "mini-skids." (BMW ABS-1.) Anyone who has dumped their bike because of locking the front wheel probably tends to be leary of trying "threshold braking" to the point of getting to "where the front end seems rubbery" or whatever other descriptive the pro's use for the point just before a crash. But ABS would be absolutely the best way of safely experiencing maximum braking. At least when the bike is upright.

2. How have BMW bike ABS systems improved since the first one? (I would hope improved reliability, but other than that?)

3. With modern bike ABS systems, is the old idea of "a quick squeeze" rather than a "sudden grab" still appropriate? (Still talking about a straight ahead stop.)

4. "Stopping in a curve," or even braking, still seems to be the topic which generates the least consensus among the "experts." Seems on this thread there is disagreement about whether the newest systems do any good at all, though maybe consensus that you can't hit the brakes when leaned well over on a wet curve with a bunch of gravel and expect all will be well. My approach (which many of you will think ridiculously conservative) is to slow down and gear down before the curve to a speed which allows me to do some engine braking while reaching for the brake lever and righting the bike in a worst case scenario.

Always more to learn.

[ANDYVH]

1. Isn't the MAIN PROBLEM with both car and bike ABS the fact that so few users "test it" until faced with a real event?
EXACTLY! I have always said any rider on any bike HAS to practice basic high effort braking skills, regularly. Same for ABS equipped bikes. Practice stops until you develop a "feel" for what you and the bike can/cannot do.

ABS on gravel is hampered by the "damming" effect of gravel piling up in front of the tire. Then, even though the ABS releases brake pressure, the lag time of the tire plowing through the gravel "dam" does indeed produce mini-skids. If it happens enough, the mini-skids can cause the ABS to go into fault mode and shut off. That's why many off-road ABS systems have an ON/OFF function.
2. How have BMW bike ABS systems improved since the first one? (I would hope improved reliability, but other than that?)
Biggest improvements are reduced weight, smaller components, higher "cycle rates" of braking pulses, and much higher computing capabilities.
3. With modern bike ABS systems, is the old idea of "a quick squeeze" rather than a "sudden grab" still appropriate? (Still talking about a straight ahead stop.)
Proper basic braking technique ALWAYS has priority, so it is better to still use the skills you know, and hopefully practice, that being the quick, progressive, increasing squeeze. If you just "grab" and either never achieve the full braking thresehold, of always exceed it, you'll never develop proper braking "feel" and you'll be over-reliant on ABS saving your butt and not knowing what you did to cause it.
4. "Stopping in a curve," or even braking, still seems to be the topic which generates the least consensus among the "experts." My approach (which many of you will think ridiculously conservative) is to slow down and gear down before the curve to a speed which allows me to do some engine braking while reaching for the brake lever and righting the bike in a worst case scenario.
Actually, I agree with your technique entirely, and use it almost all the time. Using this technique does not also make you a slow pace rider. Smooth, consistent traction and minimal chassis pitching are part of my riding style, and I tend to be somewhat quicker through the turns actually. I also do not depend or expect ABS to do anything for me when I am already leaned into a turn. Again, back to good basics. Scan/search BEFORE the turn, setup BEFORE the turn, slow-in/roll-up (throttle) through the turn, look to the exit. Doing this helps to mininmize reliance on any system other than the best one, between your ears, which is the only true Motorcycle Stability system.

[ANDYVH]

In the past I had discussed ABS systems on cycles with David Hough and Ken Condon. We pretty much all agreed that ABS can really only be relied upon for braking and stability when the bike is vertical or as near vertical as possible.

I recently emailed back and forth with Keith Code on this same subject. After about three rounds of emails I got this back from Keith, "For sure, the best advice for anyone is to get the bike as vertical as possible for any braking maneuver, ABS or not, especially on the road."

[GlobalRider]

ABS-less by choice, even if it were FREE.

[GlobalRider]

In the past I had discussed ABS systems on cycles with David Hough and Ken Condon. We pretty much all agreed that ABS can really only be relied upon for braking and stability when the bike is vertical or as near vertical as possible.

Been posting that on forums well over ten years ago, long before I even heard of those two.

Its basic physics...not rocket science!

[ANDYVH]

True, I agree. It aint rocker science for sure.

But I bet a lot of cycle riders, even those who did well in High School or College physics classes still think ABS will help them when leaned over in a turn.

[GlobalRider]

True, I agree. It aint rocker science for sure.

But I bet a lot of cycle riders, even those who did well in High School or College physics classes still think ABS will help them when leaned over in a turn.

Have them look up "traction circle".

[ANDYVH]

Yeah, I live the "traction circle" as a MSF instructor of 20 years. But actually, living in the traction circle really brings a lot of riding into perspective as far as what you can expect, and what you can do.