Servo brakes

[AnRSguy]

Servo failures have proven to be far more reliable than final drives, spines and several other components on BMW's.

 

That's not exactly a glowing endorsement.

 

Nor is it a really relevant comparison. If we're discussing reliability, servo-assisted brakes ought to be compared against the non-servo system they replace, in which case they come up short.

 

 

The main complaint has been the danger factor should they fail, so comparing them to final drive and spline failures is relavent as those can be just as catastropic. But at least in a servo failure residual braking is still there, not ideal, but it does function, with the other two in the wrong situation you are toast.

[Joe Frickin' Friday]

The main complaint has been the danger factor should they fail, so comparing them to final drive and spline failures is relavent as those can be just as catastropic. But at least in a servo failure residual braking is still there, not ideal, but it does function, with the other two in the wrong situation you are toast.

 

Certainly there have been close calls, but I'm not aware of any crashes resulting from any of the three failures you mention (spline, servo-brake, or FD). Any of these failures can cut short a vacation. But when choosing between two bikes:

 

Bike A: splines + FD + traditional brakes

 

Bike B: same splines + same FD + servo-assisted brakes

 

Bike A is going to be more reliable.

[AnRSguy]

The main complaint has been the danger factor should they fail, so comparing them to final drive and spline failures is relavent as those can be just as catastropic. But at least in a servo failure residual braking is still there, not ideal, but it does function, with the other two in the wrong situation you are toast.

 

Certainly there have been close calls, but I'm not aware of any crashes resulting from any of the three failures you mention (spline, servo-brake, or FD). Any of these failures can cut short a vacation. But when choosing between two bikes:

 

Bike A: splines + FD + traditional brakes

 

Bike B: same splines + same FD + servo-assisted brakes

 

Bike A is going to be more reliable.

 

Considering the very few servo failures reported, it would be a miniscule difference.

[smiller]

Not to defend servo brakes, just to voice my experience: R1150 servo brakes are ridable without the servo, carefully, with strong hand and foot

Yeah, I just meant that one would not be inclined to continue a trip with an 1150 servo brake failure, or at least not a very enjoyable one. And yes, this is not so much a concern on the hexhead bikes. With those the only drawbacks are the complexity, maintenance, and brake feel issues.

[T__]

Just got back from doing some comparison sitting amongst Japan, Inc and a few BMWs and it seems that one member of this household has fallen in love w/an R1150RS.

 

It has the servo brakes but I don't know about them other than they source of nearly as much animosity as paper/plastic, metlzer/dunlop nicky/roger lee...

 

Can someone give me a primer on how the work and the implications for them without a (coffee) bar fight breaking out?

 

 

Matt, the servo assist brakes on the BMW work just like the power brakes in your automobile.. Well actually more like the power brakes in a diesel powered vehicle as the servo assist uses an electric motor/pump rather than engine vacuum for the braking apply assist.. When you apply either the front or rear brake a servo motor comes on & adds braking force in direct proportion to the riders lever/pedal input.. In fact the riders input only applies pressure to a transducer inside the ABS controller & the controller actually applies the motorcycle brakes..

 

Obviously the linked part is about the same as the non power assisted linked braking systems.. The non-linked systems are slightly different with either front or rear rider input force required to get braking on that end.. Even on the linked evo systems you can get front or rear biased braking under light to moderate braking by using the hand lever or rear brake pedal.. Just look at your brake rotor color after moderate braking & if only the front lever is used the front rotors will be dark with the rear rotor being light colored.. If only the rear brake pedal is used the rear rotor will be darker than the front rotors (this only applies to light & moderate braking, heavy braking the system goes to total internal front/rear adaptive bias control)..

 

The servo assist (evo) BMW braking system also comes with an adaptive braking algorithm that learns the tire friction thresholds & automatically adjusts the braking forces to keep the system balanced.. If you put a passenger or extra weight on the rear of the bike the adaptive part of the system quickly figures that out & adjusts the front rear braking bias accordingly..

 

On dry road max G stopping the BMW ABS & non ABS will stop at about the same rate with a very experienced professional rider possibly stopping in slightly less distance (provided he doesn’t overbrake & slip a tire).. On wet road max G stopping the minimum stopping distance usually goes to the ABS system as the rider can apply more braking power without worry of locking a wheel & going down… On a chatter bump road, frost heave road, or gravel road situation the non ABS system will usually out brake the ABS system provided the rider doesn’t lock a wheel long enough to go down..

 

BMW’s thinking ( & rightfully so) on using the servo assist braking system was two fold.. The first was it allowed the rider to get to max brake pressure therefore max braking force sooner than the a conventional non power assisted system.. The second reason was it allowed the ABS computer to do all the braking so the response times on the ABS was quicker than a non assisted system (at the time of the evo system release).. Since the time of the first evo systems the conventional (non power assisted) ABS systems have advanced to the point that their response times are as good if not better than the older evo servo systems..

 

I have been riding a servo assisted BMW for quite a while now & would say I really like it.. The stopping power is just fantastic at high end freeway speeds, the braking force modulation takes some getting used to but once it becomes second nature it is no different than any other braking system.. If I had one complaint about the system it would be the very low speed aggressiveness of the braking system with the front wheel turned at or near the steering lock (until you are used to it it’s easy to stop too quickly at very low speeds & upset the bike’s balance)..

 

It does seem that BMW riders fall into two categories,, those that like the evo servo assist brakes & those that can’t adjust to the system therefore don’t like the system..

 

This being a BMW web site you usually hear the bitching more than the good.. Hardly anyone starts a thread to say they like something, it’s usually a thread to complain about something..

 

My suggestion would be to go hang out at your local BMW dealer on a Saturday morning & take a poll of the riders that come in on servo assisted brake bikes.. It won’t take you long to figure out what the average rider has to say about the servo braking system (both good & bad)..

 

While there have probably been a few evo servo brake controller failures there can’t be very many as I see no recalls on that particular BMW braking system.. ANY time there is more than a few brake related failures it brings on NHTSA intervention quicker than you can blink so there can’t be many..

 

I would suggest if you do buy a servo assist braking system that you shut down the controller then ride the bike to get a feel for the added rider braking input force required to achieve safe stopping power & distance.. Once you get used to it, it is very controllable & not all that bad.. It does help to set the front brake lever position to a longer travel position & it is a must that you use both the front & rear brake pedal/lever to get minimum stopping distance..

 

 

Twisty

[smiller]

It does seem that BMW riders fall into two categories,, those that like the evo servo assist brakes & those that can’t adjust to the system therefore don’t like the system.

Well, actually there are additional categories of thought running through just about every servo brake thread.

[ully211]

Been riding my '02 RT1150 with the Servo brakes for five years now ... and I agree COMPLETELY with Twisty ... THANKS!

[Jim VonBaden]

1, and maintenance is easy as well, plus they have not proven to fail like everyone predicted.

 

BS.

 

They're a mechanical component...they can, and DO fail. We've had several reports of servo pump failures just here on this forum.

 

Frequently? No.

 

But it does happen.

 

And no, it doesn't make the bike impossibly difficult to work on, but it is substantially more time consuming to work on than the Non-servo ABS-II system.

 

Servo brakes would not prevent be from buying a bike that was otherwise "the one" (assuming they were not linked, or partially linked) but given the choice, I'll take the simpler, cheaper, easier to work on system that gives better feel and feedback, doesn't have the wonderful "ice patch" anti-stoppie "feature", and doesn't leave you with a fraction of your normal braking power with no warning in the event that it does fail.

 

BS To what? There are just as many failures of non abs-nonservo brake systems as there are servo-brakes. Just check out ADVRider's issues with the new 07 non-servo-ABS systems. Believe me, I notice every failure, some of which resulted in locked, or no brakes at all. Burst hoses, bad master cylinders, locked up rear brakes, like you said, it is mechanical, and mechanical things break.

 

Or is it you just don't like others to have a different opinion than you?

 

I can do my brake service in just over an hour, less if combined with other services, sure a little longer than non-servo systems, but hardly a difficult job.

 

I actually like the servos because I can single finger near panic stops, not possible with conventional brakes unless you are a gorillia!

 

But hey, you are certainly entitled to your opinion, no matter how wrong it is.

 

Jim

[russell_bynum]

The servo assist (evo) BMW braking system also comes with an adaptive braking algorithm that learns the tire friction thresholds & automatically adjusts the braking forces to keep the system balanced.. If you put a passenger or extra weight on the rear of the bike the adaptive part of the system quickly figures that out & adjusts the front rear braking bias accordingly..

 

Help me understand that statement.

 

My (limited) understand of how ABS works, is the computer is looking at the input from the wheel speed sensors. When one of the wheels accelerates at a rate that is higher than the preset threshold, the computer assumes it is starting to slide, and engages ABS for that wheel.

 

Now...I know there's a bit more "smarts" built into the servo system like the anti-stoppie "feature" (Like there was ever a problem of a bunch of RT riders accidentally doing endos while braking hard.) but the basic way the ABS works is it just looks for that sudden acceleration of a wheel.

 

What am I missing?

 

BMW’s thinking ( & rightfully so) on using the servo assist braking system was two fold.. The first was it allowed the rider to get to max brake pressure therefore max braking force sooner than the a conventional non power assisted system.. The second reason was it allowed the ABS computer to do all the braking so the response times on the ABS was quicker than a non assisted system (at the time of the evo system release).. Since the time of the first evo systems the conventional (non power assisted) ABS systems have advanced to the point that their response times are as good if not better than the older evo servo systems..

 

I disagree with the first reason. With my RT (ABS-II) It was quite easy to apply enough braking force quickly enough to overwhelm the compression damping circuits on the front shock, bottom the front forks, and lock the front tire....using one finger on the non-servo assisted lever. In other words: It was already easy to apply "max" braking force faster than the rest of the system (suspension and chassis) can handle it...so using servos to do that even faster doesn't buy you anything.

 

I agree on the second point...servos allow the computer to totally ignore the rider's inputs (if necessary/desirable) and apply exactly as much pressure to each wheel as it sees fit. There's some benefit to that.

 

It does seem that BMW riders fall into two categories,, those that like the evo servo assist brakes & those that can’t adjust to the system therefore don’t like the system..

 

Wrong.

 

I despise the "fully linked" brakes on the R1150RT. I will not tolerate that system. Period. But...I've got quite a few miles on the '02 and later K1200RS, which has the partially linked servo system. I have no complaints about the day-to-day operation of those brakes. I prefer the feel and feedback of the non-servo systems, I don't see any reason to have the servo system, and I don't like the liabilities that the servo system brings to the equation, but it took me less than 100 miles to adapt to the system so that I could make it do what I wanted it to do. As I said earlier in this thread...if I found "the bike" but it had unlinked or partially linked servo brakes, I'd buy it and it wouldn't impact my day-to-day enjoyment of the bike at all.

 

While there have probably been a few evo servo brake controller failures there can’t be very many as I see no recalls on that particular BMW braking system.. ANY time there is more than a few brake related failures it brings on NHTSA intervention quicker than you can blink so there can’t be many..

 

There haven't been any spline or final drive recalls either.

 

As I said...servo failure is not common, but it DOES happen. It isn't something I'd ride around in mortal fear that it was going to happen at any minute, but the systems do occasionally fail. And when they do, you are left with puny brakes and a VERY expensive repair bill. (By comparison...if the ABS pump on my ABS-II bike dies. my brakes still work just fine...I just lose ABS functionality.)

[Ken H.]

But when choosing between two bikes:

 

Bike A: splines + FD + traditional brakes

 

Bike B: same splines + same FD + servo-assisted brakes

 

Bike A is going to be more reliable.

Are you saying that just because of concept: More complicated = less reliable, or specific to the track history of the BMW servo brakes?

 

If the former I'm not necessary sure there is a proved correlation. Many products today are more complicated than they were 20 years ago, yet are more reliable.

[russell_bynum]

But when choosing between two bikes:

 

Bike A: splines + FD + traditional brakes

 

Bike B: same splines + same FD + servo-assisted brakes

 

Bike A is going to be more reliable.

Are you saying that just because of concept: More complicated = less reliable, or specific to the track history of the BMW servo brakes?

 

If the former I'm not necessary sure there is a proved correlation. Many products today are more complicated than they were 20 years ago, yet are more reliable.

 

The Mean Time Before Failure of a system that does not exist, is infinite.

[Joe Frickin' Friday]

But when choosing between two bikes:

 

Bike A: splines + FD + traditional brakes

 

Bike B: same splines + same FD + servo-assisted brakes

 

Bike A is going to be more reliable.

Are you saying that just because of concept: More complicated = less reliable...

 

yes. If you have two identical systems, and you add components to one of them, you've necessarily decreased its reliability. In this case, you've got two identical bikes, except one of them also has servo-assist: that servo-assisted model will be less reliable than the non-servo-assisted model.

 

If the former I'm not necessary sure there is a proved correlation. Many products today are more complicated than they were 20 years ago, yet are more reliable.

 

A product from 20 years ago has almost nothing in common with a recent-vintage product. Take a 1987 Honda Accord, and compare it to a 2007 Accord, and in addition to making it more complex, they've re-engineered everything. It's not at all the same as comparing a 2001 R1100RT to a 2002 R1150RT.

[Dave_zoom_zoom]

Jim

 

I think Russell means you make the Best Sense !!!!!

(I could be wrong)

 

Dave

[RPG]

check out http://www.largiader.com/abs/abs2.html

 

for complete info on how ABS II works.

 

My opinion: wouldn't have another bike without it.

 

RPG

[MadDuck]

I come down on the simple fact that BMW completely redesigns the ABS system on average every three years. If any of these systems were as good as they are claimed to be that cycle time would be more like ten years. My guess is that there are many more problems with each of the systems than we on this board know about. My next BMW will be without expensive to repair/maintain options. I'm thinking R1200R with windshield and bags and no other options. Sort of the Harley of BMW's.

[T__]

The servo assist (evo) BMW braking system also comes with an adaptive braking algorithm that learns the tire friction thresholds & automatically adjusts the braking forces to keep the system balanced.. If you put a passenger or extra weight on the rear of the bike the adaptive part of the system quickly figures that out & adjusts the front rear braking bias accordingly..

 

Help me understand that statement.

 

My (limited) understand of how ABS works, is the computer is looking at the input from the wheel speed sensors. When one of the wheels accelerates at a rate that is higher than the preset threshold, the computer assumes it is starting to slide, and engages ABS for that wheel.

 

Now...I know there's a bit more "smarts" built into the servo system like the anti-stoppie "feature" (Like there was ever a problem of a bunch of RT riders accidentally doing endos while braking hard.) but the basic way the ABS works is it just looks for that sudden acceleration of a wheel.

 

What am I missing?

 

BMW’s thinking ( & rightfully so) on using the servo assist braking system was two fold.. The first was it allowed the rider to get to max brake pressure therefore max braking force sooner than the a conventional non power assisted system.. The second reason was it allowed the ABS computer to do all the braking so the response times on the ABS was quicker than a non assisted system (at the time of the evo system release).. Since the time of the first evo systems the conventional (non power assisted) ABS systems have advanced to the point that their response times are as good if not better than the older evo servo systems..

 

I disagree with the first reason. With my RT (ABS-II) It was quite easy to apply enough braking force quickly enough to overwhelm the compression damping circuits on the front shock, bottom the front forks, and lock the front tire....using one finger on the non-servo assisted lever. In other words: It was already easy to apply "max" braking force faster than the rest of the system (suspension and chassis) can handle it...so using servos to do that even faster doesn't buy you anything.

 

I agree on the second point...servos allow the computer to totally ignore the rider's inputs (if necessary/desirable) and apply exactly as much pressure to each wheel as it sees fit. There's some benefit to that.

 

It does seem that BMW riders fall into two categories,, those that like the evo servo assist brakes & those that can’t adjust to the system therefore don’t like the system..

 

Wrong.

 

I despise the "fully linked" brakes on the R1150RT. I will not tolerate that system. Period. But...I've got quite a few miles on the '02 and later K1200RS, which has the partially linked servo system. I have no complaints about the day-to-day operation of those brakes. I prefer the feel and feedback of the non-servo systems, I don't see any reason to have the servo system, and I don't like the liabilities that the servo system brings to the equation, but it took me less than 100 miles to adapt to the system so that I could make it do what I wanted it to do. As I said earlier in this thread...if I found "the bike" but it had unlinked or partially linked servo brakes, I'd buy it and it wouldn't impact my day-to-day enjoyment of the bike at all.

 

While there have probably been a few evo servo brake controller failures there can’t be very many as I see no recalls on that particular BMW braking system.. ANY time there is more than a few brake related failures it brings on NHTSA intervention quicker than you can blink so there can’t be many..

 

There haven't been any spline or final drive recalls either.

 

As I said...servo failure is not common, but it DOES happen. It isn't something I'd ride around in mortal fear that it was going to happen at any minute, but the systems do occasionally fail. And when they do, you are left with puny brakes and a VERY expensive repair bill. (By comparison...if the ABS pump on my ABS-II bike dies. my brakes still work just fine...I just lose ABS functionality.)

 

Russell, the BMW evo ABS braking system uses adaptive braking.. That is basically electronic fuzzy logic force distribution.. The electronic processor in the ABS controller monitors brake pressure vs wheel speeds/ wheel decel speeds,, & also monitors brake input pressure in the rear braking circuit vs rear wheel circuit pressure then adjusts the rear wheel braking pressure accordingly.. The FAG Kugelfischer actual algorithms are proprietary so I don’t have access to the details of the adaptive programming.. Based on other similar type systems my guess would be it uses a fixed mapping for basic braking force distribution then modifies it from that as the rear wheel decel rates fall above or below basic values dictated by the input pressure & brake circuit pressures.. The detached servo function will allow the system to add or remove wheel circuit braking pressure as needed to keep the decel rates even front to rear..

The BMW evo braking system has a suggested release response time of 80 milliseconds with a response time as low as 50 milliseconds under certain conditions (you can’t even come close there doing it yourself).. The system can also vary the response frequency from around .6Hz to as slow as 5 Hz on really slick or gravel roads.. With a non servo system you can’t get close to the pressure build times on the evo braking system either as it not only uses motor/pump pressure assist but also uses a very short lever stroke so you get a very fast pressure build for a very short stroke & it can move massive amounts of fluid very quickly..

 

Twisty

[ghaverkamp]

*sigh*

 

EVO brakes are not Integral ABS and have nothing to do with servos.

[russell_bynum]

Russell, the BMW evo ABS braking system uses adaptive braking.. That is basically electronic fuzzy logic force distribution.. The electronic processor in the ABS controller monitors brake pressure vs wheel speeds/ wheel decel speeds,, & also monitors brake input pressure in the rear braking circuit vs rear wheel circuit pressure then adjusts the rear wheel braking pressure accordingly.. The FAG Kugelfischer actual algorithms are proprietary so I don’t have access to the details of the adaptive programming.. Based on other similar type systems my guess would be it uses a fixed mapping for basic braking force distribution then modifies it from that as the rear wheel decel rates fall above or below basic values dictated by the input pressure & brake circuit pressures.. The detached servo function will allow the system to add or remove wheel circuit braking pressure as needed to keep the decel rates even front to rear..

 

 

Why would the relative decel rates of each wheel be relevant? What do you gain by doing that vs. watching each wheel for acceleration that's outside of the specified range, and reacting to that?

 

 

 

The BMW evo braking system has a suggested release response time of 80 milliseconds with a response time as low as 50 milliseconds under certain conditions (you can’t even come close there doing it yourself).. The system can also vary the response frequency from around .6Hz to as slow as 5 Hz on really slick or gravel roads.. With a non servo system you can’t get close to the pressure build times on the evo braking system either as it not only uses motor/pump pressure assist but also uses a very short lever stroke so you get a very fast pressure build for a very short stroke & it can move massive amounts of fluid very quickly..

 

I have no doubt that the servos can get pressure to the system faster than I can. And I have no doubt that it can deliver more pressure than I can.

 

My point was...I'm already capable of providing too much, too fast...so something that can provide even more even faster is of no benefit whatsoever.

[T__]

Why would the relative decel rates of each wheel be relevant? What do you gain by doing that vs. watching each wheel for acceleration that's outside of the specified range, and reacting to that? {/quote]

 

 

Russell, the system could care less about wheel acceleration, it looks for wheel deceleration..

 

Maybe you don’t care about relative wheel decel rates but I sure do.. If the rear wheel is deceling faster than the front it means it is slipping more than the front so the system transfers more braking force to the front wheel.. You do the same thing when you use both the front & rear brake on a conventional system.. How do you suppose a LINKED system knows how much front & rear brake to use under what conditions? In a conventional linked system it doesn’t so you get what you get.. In an adaptive system it learns as it stops so basically learns just like a rider would.. What do you do with the rear brake as the stopping force & bike weight is transferred to the front? Start letting the rear pressure up right.. Well a smart linked system does the same thing..

 

 

My point was...I'm already capable of providing too much, too fast...so something that can provide even more even faster is of no benefit whatsoever.

 

You are probably capable of providing too much but I doubt too fast.. We’re not always talking max pressure or max possible, just time-to-pressure.. The evo system will beat you to 50 pounds, will beat you to 100 pounds, will beat you to 1000 pounds.. I know it’s probably only a couple of hundredths of a second but that is stopping distance gained..

 

Twisty

[Tapatio]

Nerd Alert!

 

Everyone stop typing and start riding.

[russell_bynum]

Russell, the system could care less about wheel acceleration, it looks for wheel deceleration..

 

Deceleration is acceleration in a negative direction. Sorry...I was using acceleration to describe "rate of change".

 

Maybe you don’t care about relative wheel decel rates but I sure do.. If the rear wheel is deceling faster than the front it means it is slipping more than the front so the system transfers more braking force to the front wheel.. You do the same thing when you use both the front & rear brake on a conventional system.. How do you suppose a LINKED system knows how much front & rear brake to use under what conditions? In a conventional linked system it doesn’t so you get what you get.. In an adaptive system it learns as it stops so basically learns just like a rider would.. What do you do with the rear brake as the stopping force & bike weight is transferred to the front? Start letting the rear pressure up right.. Well a smart linked system does the same thing..

 

OK, I'm following you there. I was operating under the (apparently mistaken??) understanding that the system was just watching each wheel for a sudden change in the rate of acceleration (deceleration in this case) and reacting to that.

 

I have in my head that the rapid change in accleration is called the "Jerk Factor"...but maybe I'm suffering from termporary insanity on this one.

 

 

My point was...I'm already capable of providing too much, too fast...so something that can provide even more even faster is of no benefit whatsoever.

 

You are probably capable of providing too much but I doubt too fast..

 

It's easy to demonstrate...zip-tie on the fork tube to mark it's position...get the bike up to speed jam on brakes really fast.

 

The forks bottom and the front locks (or ABS engages).

 

Now...I don't have a force gauge on my brakes to measure the difference, but I'm pretty sure that when I bring the brakes up to pressure more gradually (over the course of about 1 second), I can apply much greater pressure.

 

This agrees with the "best practices" for braking that I've read from pretty much every expert. Let's say the system (and by "system"...I mean the whole tire/suspension/chassis/road combination) can withstand a maximum of 500lbs of brake pressure at 50mph. If you just jam on the brakes, you slam the weight forward too quickly...it overwhelms the suspension, and the tire locks. You have to bring the sytem up to that maximum pressure smoothly to allow the weight to transfer forward and the suspension to do it's thing. The bike is not in a configuration to accept "maximum" brake pressure under normal situations as you're just riding down the road. An example of how the "Maximum" changes is how you have to ease the pressure on the rear brake as the weight transfers forward.

 

 

We’re not always talking max pressure or max possible, just time-to-pressure.. The evo system will beat you to 50 pounds, will beat you to 100 pounds, will beat you to 1000 pounds..

 

I totally agree that the system can beat me to pretty much any pressure.

 

I'm saying that's not a good thing.

 

If anything...the "ideal" system would see me suddenly jam on the brakes, ignore that, and gradually ramp the pressure up on it's own.

[Huzband]

I have it on good authority that Matt hasn't looked at this thread since Sunday.

 

He was looking for facts, not opinion.

 

Now that I've said that, ya'll feel free to fight amongst yourselves.

 

[tallman]

Who's Matt?

And why is he looking for thread?

Did he brake something?

[Huzband]

Who's Matt?

 

Why, he's the guy on your door step.

[Jim VonBaden]

Jim

 

I think Russell means you make the Best Sense !!!!!

(I could be wrong)

 

Dave

 

If that is the case my reading comprehension sucks, though Russell's response to Twisty1 seems to refute it.

 

Thanks!

 

Jim

[Joe Frickin' Friday]

Maybe you don’t care about relative wheel decel rates but I sure do.. If the rear wheel is deceling faster than the front it means it is slipping more than the front so the system transfers more braking force to the front wheel.. You do the same thing when you use both the front & rear brake on a conventional system.. How do you suppose a LINKED system knows how much front & rear brake to use under what conditions? In a conventional linked system it doesn’t so you get what you get.. In an adaptive system it learns as it stops so basically learns just like a rider would.. What do you do with the rear brake as the stopping force & bike weight is transferred to the front? Start letting the rear pressure up right.. Well a smart linked system does the same thing..

 

OK, I'm following you there. I was operating under the (apparently mistaken??) understanding that the system was just watching each wheel for a sudden change in the rate of acceleration (deceleration in this case) and reacting to that.

 

I have in my head that the rapid change in accleration is called the "Jerk Factor"...but maybe I'm suffering from termporary insanity on this one.

 

Wikipedia mentions the computer comparing any given wheel's speed with the speeds of the other wheels, but then again, that's Wikipedia.

 

Bill, the Bosch Automotive Handbook is in agreement with Russell, and it's how I thought ABS worked. Admittedly mine is getting old now (3rd edition, they're up to 6 now), but the basic ABS explanation they provide is that the computer is watching for a sudden increase in wheel accel(uh, deceleration): when the wheel goes beyond the static traction limit and begins to skid, the available traction force decreases, and the excess brake torque results in extremely rapid wheel deceleraation. The computer is watching for that transition-edge between "normal" and "ridiculous" deceleration (a spike in the "jerk" function), and that's when the ABS kicks in. No need to monitor another wheel for comparison purposes.

 

In fact, if all four wheels on the car (or both wheels on the bike) are experiencing ABS activity, then no single wheel can be counted on to give a reliable reference measure of true vehicle speed: there can be no comparison. Each wheel must be able to manage its ABS activity independently.

 

As far as a linked system knowing how much front and rear brake to provide during varying conditions: "linked," "ABS," and "servo-assist" are separate things. There have been linked, non-ABS systems out there on motorcycles before, and in fact this was the norm on cars for decades via a proportioning valve, with the front/rear braking distribution pre-selected at the factory to correspond with 4-wheel lockup using "normal" tires on "normal" pavement. Granted, if you were using sticky tires on "great" pavement your rears would lockup well before the front; conversely, in the snow, your fronts would lock up first.

 

"Adaptive linked braking" just sounds like ordinary linked brakes (utilizing a pre-defined front/rear braking distribution designed to result in simultaneous front/rear lockup using normal tires on normal pavement) with ABS added on.

[RPG]

I come down on the simple fact that BMW completely redesigns the ABS system on average every three years. If any of these systems were as good as they are claimed to be that cycle time would be more like ten years. My guess is that there are many more problems with each of the systems than we on this board know about. My next BMW will be without expensive to repair/maintain options. I'm thinking R1200R with windshield and bags and no other options. Sort of the Harley of BMW's

 

I hear what you're saying but I look at it the other way. I presume the design is sound from the start and changes are made every three years to evolve and improve the system/product, just as BMW has always done over the years. In that regard I am glad they don't wait 10 years.

 

RPG

[T__]

Maybe you don’t care about relative wheel decel rates but I sure do.. If the rear wheel is deceling faster than the front it means it is slipping more than the front so the system transfers more braking force to the front wheel.. You do the same thing when you use both the front & rear brake on a conventional system.. How do you suppose a LINKED system knows how much front & rear brake to use under what conditions? In a conventional linked system it doesn’t so you get what you get.. In an adaptive system it learns as it stops so basically learns just like a rider would.. What do you do with the rear brake as the stopping force & bike weight is transferred to the front? Start letting the rear pressure up right.. Well a smart linked system does the same thing..

 

OK, I'm following you there. I was operating under the (apparently mistaken??) understanding that the system was just watching each wheel for a sudden change in the rate of acceleration (deceleration in this case) and reacting to that.

 

I have in my head that the rapid change in accleration is called the "Jerk Factor"...but maybe I'm suffering from termporary insanity on this one.

 

Wikipedia mentions the computer comparing any given wheel's speed with the speeds of the other wheels, but then again, that's Wikipedia.

 

Bill, the Bosch Automotive Handbook is in agreement with Russell, and it's how I thought ABS worked. Admittedly mine is getting old now (3rd edition, they're up to 6 now), but the basic ABS explanation they provide is that the computer is watching for a sudden increase in wheel accel(uh, deceleration): when the wheel goes beyond the static traction limit and begins to skid, the available traction force decreases, and the excess brake torque results in extremely rapid wheel deceleraation. The computer is watching for that transition-edge between "normal" and "ridiculous" deceleration (a spike in the "jerk" function), and that's when the ABS kicks in. No need to monitor another wheel for comparison purposes.

 

In fact, if all four wheels on the car (or both wheels on the bike) are experiencing ABS activity, then no single wheel can be counted on to give a reliable reference measure of true vehicle speed: there can be no comparison. Each wheel must be able to manage its ABS activity independently.

 

As far as a linked system knowing how much front and rear brake to provide during varying conditions: "linked," "ABS," and "servo-assist" are separate things. There have been linked, non-ABS systems out there on motorcycles before, and in fact this was the norm on cars for decades via a proportioning valve, with the front/rear braking distribution pre-selected at the factory to correspond with 4-wheel lockup using "normal" tires on "normal" pavement. Granted, if you were using sticky tires on "great" pavement your rears would lockup well before the front; conversely, in the snow, your fronts would lock up first.

 

"Adaptive linked braking" just sounds like ordinary linked brakes (utilizing a pre-defined front/rear braking distribution designed to result in simultaneous front/rear lockup using normal tires on normal pavement) with ABS added on.

 

Mitch, it’s not a Bosch ABS unit so anything from them isn’t applicable..

 

The (about all modern) ABS systems don’t look for wheel lock up anymore.. By then it’s too late to release in time on ice or very slippery conditions, or a wheel off the road.. They look for impending lock up.. There are pre programmed decel rates internal to the ABS mapping that looks at current wheel speed, just recent wheel speed, & current wheel decel rate, on automobiles it usually looks at 4 wheel average also.. It knows that a wheel that was spinning at 60 mph a second ago & is now spinning at 20 mph is in impending lock up so releases some braking force on that wheel.. It’s only when the wheel doesn’t respond that it goes into ABS control & fully releases the wheel.. The modern ABS units can also vary the cycle rate of the ABS in relation to the road surface traction available.. On good dry road you want a very fast cyclic rate as the wheel starts it’s spool up instantly.. On ice or gravel you want a slow cyclic rate as the wheel can’t recover it’s traction fast enough to spool up again quickly..

 

I guess I don’t give a hoot if you guys believe me or not but the new generation ABS units are very smart & have both adaptive & learning capabilities.. Most trucks have had adaptive ABS systems for quite a while now as the ABS was used for front rear brake proportioning & they don’t require the system to enter ABS mode to get the proportioning.. If they used ABS brake release for proportioning the stopping distance would go way long..

 

AFAIK, the BMW Integral ABS with evo front brake DOES use a pre-defined brake front/rear bias but that is JUST A STATRING POINT.. It learns from there & adapts to available traction on each end then distributes the braking pressure accordingly.. I don’t have first hand info on the full learning ability of the BMW integral ABS but if like adaptive units I am familiar with it only functions at moderate to heavy braking & uses a fixed speed vs input pressure selected mapping for light & light/moderate braking functions..

 

If you guys don’t like this system just wait a few years as brake by wire with no hydraulics is in your future.. Now those systems that I have driven so far don’t impress me one bit yet..

 

Twisty

[HexHead]

My next BMW will be without expensive to repair/maintain options.

 

That would be a Ural.

[HexHead]

The servo assist (evo) BMW braking system also comes with an adaptive braking algorithm that learns the tire friction thresholds & automatically adjusts the braking forces to keep the system balanced.. If you put a passenger or extra weight on the rear of the bike the adaptive part of the system quickly figures that out & adjusts the front rear braking bias accordingly..

 

Twisty, Great description of the system. Just one thing to add (or clarify) though. You can override the bias by using the rear brake pedal also. If you apply more pressure than what the system would use just by just pulling the front brake lever, it will add the additional braking power to the rear.

[HexHead]

The servo assist (evo) BMW braking system also comes with an adaptive braking algorithm that learns the tire friction thresholds & automatically adjusts the braking forces to keep the system balanced.. If you put a passenger or extra weight on the rear of the bike the adaptive part of the system quickly figures that out & adjusts the front rear braking bias accordingly..

 

Help me understand that statement.

 

He's correct. When you turn on the bike, the first five times you apply the brakes, the EVO system is measuring the weight load and tire friction and adjusts the front/rear bias accordingly. It continues to update this each time you use the brakes until the next time you start the bike, at which time it starts the process over again.

[Joe Frickin' Friday]

He's correct. When you turn on the bike, the first five times you apply the brakes, the EVO system is measuring the weight load and tire friction and adjusts the front/rear bias accordingly. It continues to update this each time you use the brakes until the next time you start the bike, at which time it starts the process over again.

 

Assuming your first five braking events aren't at the edge of traction, how does the system measure tire friction? Also, how does it measure weight loading on each tire?

[smiller]

He's correct. When you turn on the bike, the first five times you apply the brakes, the EVO system is measuring the weight load and tire friction and adjusts the front/rear bias accordingly. It continues to update this each time you use the brakes until the next time you start the bike, at which time it starts the process over again.

It also knows how you like your eggs.

[T__]

 

Right from BMW Motorrad

 

 

 

ADVANTAGES OF BMW'S NEW INTEGRAL ABS

 

• Reliable anti-lock brake management.

• Faster ABS response.

• Monitoring of the tail and brake lights.

• Dimmed brake light replacing the taillight should the latter fail to operate.

• Up to 20 per cent more brake power and approximately 15 per cent lower handbrake forces for the same brake power thanks to the new EVO front wheel brake.

• Approximately 50 per cent lower brake operating forces thanks to brake servo and the EVO front wheel brake.

• Faster build-up of brake pressure and very good deceleration ensured by the brake power servo and integral brake system.

• Fully or partly integrated system, depending on the type (character) of motorcycle.

• Maximum brake effect on both wheels thanks to the integral brake system, even when pulling only one brake lever.

• More consistent spread of forces on both brakes thanks to the integral brake system.

• Perfect distribution of ideal brake forces on the front and rear wheel ensured by adaptive brake force distribution.

• Adaptive, self-learning brake force distribution ensuring perfect distribution of ideal brake forces on the front and rear wheel.

• Lateral guidance of wheels enhanced to an optimum by adaptive brake force distribution.

• Entire system even more compact and more than 20 per cent lighter.

• Diagnostic unit continually monitors the entire system.

[Bob Palin]

Right from BMW Motorrad Marketing Department

 

ADVANTAGES OF BMW'S NEW INTEGRAL ABS

Fixed

[motoguy128]

There is a possible way it could measure load and braking performance. It could measure the hydralic line pressure in the front and rear brakes and that generated at the hand lever. It then only needs an accelerometer to measure the braking performance. Although until a wheel actually lock-up, it's still only guessing at the ideal F/R bias.

 

However Brake force distribution as on a car is still possible. All this really does is prevent the need to pull harder on the lever as traction is lost, the system will send more pressure to the wheels that still have traction. In an alder ABS system, you would need to push harder to get more force to the other wheels with traction. These system I beleive also need to employ aan accleratmetes since if all 4 wheels are nearly locked, there is no longer any speed reference available. An acclerometer can calculate a virtual speed reference rather than relying on an average speed of all wheels. 1 lateral accelerometer is used at each end of the vehicle for stability control. This would be pretty hard to do correctly on a motorcycle since the dynamics of lean angle and steering input are diffucult to measure and control.

 

 

IN SUMMARY... it's definitely a marketing tool. The claims are pretty broad and don't make a specific claim.

[John in VA]

Right from BMW Motorrad

ADVANTAGES OF BMW'S NEW INTEGRAL ABS

 

• Monitoring of the tail and brake lights.

• Dimmed brake light replacing the taillight should the latter fail to operate.

 

I take it this no longer applies to the CanBus bikes in which the tail and brake lights are one and the same?

[russell_bynum]

Right from BMW Motorrad Marketing Department

 

ADVANTAGES OF BMW'S NEW INTEGRAL ABS

Fixed

 

No kidding.

[IanW]

Right from BMW Motorrad

 

 

 

ADVANTAGES OF BMW'S NEW INTEGRAL ABS

 

• Reliable anti-lock brake management.

• Faster ABS response.

• Monitoring of the tail and brake lights.

• Dimmed brake light replacing the taillight should the latter fail to operate.

• Up to 20 per cent more brake power and approximately 15 per cent lower handbrake forces for the same brake power thanks to the new EVO front wheel brake.

• Approximately 50 per cent lower brake operating forces thanks to brake servo and the EVO front wheel brake.

• Faster build-up of brake pressure and very good deceleration ensured by the brake power servo and integral brake system.

• Fully or partly integrated system, depending on the type (character) of motorcycle.

• Maximum brake effect on both wheels thanks to the integral brake system, even when pulling only one brake lever.

• More consistent spread of forces on both brakes thanks to the integral brake system.

• Perfect distribution of ideal brake forces on the front and rear wheel ensured by adaptive brake force distribution.

• Adaptive, self-learning brake force distribution ensuring perfect distribution of ideal brake forces on the front and rear wheel.

• Lateral guidance of wheels enhanced to an optimum by adaptive brake force distribution.

• Entire system even more compact and more than 20 per cent lighter.

• Diagnostic unit continually monitors the entire system.

 

Twisty

This was new in 2002. (hey that rhymes)

Ian

[MadDuck]

Rumour has it that BMW has been foisting off ABS on an unsuspecting public as the only effective way to get police departments to switch from Harleys. Require something called ABS, whether its better or not and you can wedge your toe into the market.

[russell_bynum]

Rumour has it that BMW has been foisting off ABS on an unsuspecting public as the only effective way to get police departments to switch from Harleys. Require something called ABS, whether its better or not and you can wedge your toe into the market.

 

I don't buy that. And if it is true, it isn't working very well because I keep seeing lots of Kawi, Harley, and even a few Honda cop bikes out there.

[Paul Mihalka]

Rumour has it that BMW has been foisting off ABS on an unsuspecting public as the only effective way to get police departments to switch from Harleys. Require something called ABS, whether its better or not and you can wedge your toe into the market.

Nonsense. BMW has ABS on bikes since 1988 without any push for police bikes.

[motorman587]

Is that why Harley is now offering ABS???? They also in 2005 only offered it to the Police, because of BMW's ABS.

[ghaverkamp]

Is that why Harley is now offering ABS???? They also in 2005 only offered it to the Police, because of BMW's ABS.

 

 

Rumor has it that Harley-Davidson has been foisting off ABS on an unsuspecting police force as the only effective way to get police departments to stay with Harleys. Require something called ABS, whether it's better or not and you can keep control of your market.

[motorman587]

Is that why Harley is now offering ABS???? They also in 2005 only offered it to the Police, because of BMW's ABS.

 

 

 

 

 

 

Rumor has it that Harley-Davidson has been foisting off ABS on an unsuspecting police force as the only effective way to get police departments to stay with Harleys. Require something called ABS, whether it's better or not and you can keep control of your market.

 

 

 

I guess that's why it is still an option on police motors for those non-motorcyclist beancounters.

[peterbulgar]

I just returned from a short vacation and only now picked up this thread. I didn't read all the posts so sorry if I repeat what has already been said:

 

ABS was a big factor in my decision to purchase a new '04 R1150RA. The ABS works fine, however IMHO the servo part of the package is annoying and unnecessary. I believe that BMW has dropped the servo system on their new bikes except the LT - if it was good why didn't they keep it? The servo is too sensitive at very low speeds, if the servo unit fails it is very expensive to replace (no repair, only replacement). I have half a million miles on motorcycles, and the only time I've dumped any bike at low speeds has been on my '04 with servo brakes. I have all the fingers on my right hand and do not need or want "one-fingered braking". I purchased the extended warranty so if the servo fails in the next couple of years I'm OK. If you buy the '03 I suggest you look into the extended warranty - and practice changing your braking habits.

Peter '73 R75/5, '04 R1150RA

[MotorinLA]

Is that why Harley is now offering ABS???? They also in 2005 only offered it to the Police, because of BMW's ABS.

 

 

Rumor has it that Harley-Davidson has been foisting off ABS on an unsuspecting police force as the only effective way to get police departments to stay with Harleys. Require something called ABS, whether it's better or not and you can keep control of your market.

 

HD added the ABS during their bid with the CHP, as it was a requirement for new CHP motorcycles. Apparently the first ABS controllers on the HDs had four terminals as they were "borrowed" from a GM car... At least the BMW ABS units were made for a motorcycle.

[motorman587]

Is that why Harley is now offering ABS???? They also in 2005 only offered it to the Police, because of BMW's ABS.

 

 

 

 

 

Rumor has it that Harley-Davidson has been foisting off ABS on an unsuspecting police force as the only effective way to get police departments to stay with Harleys. Require something called ABS, whether it's better or not and you can keep control of your market.

 

HD added the ABS during their bid with the CHP, as it was a requirement for new CHP motorcycles. Apparently the first ABS controllers on the HDs had four terminals as they were "borrowed" from a GM car... At least the BMW ABS units were made for a motorcycle.

 

 

Yup, and I have a picture of it. It was a large box on the right saddle bag. It took up 1/2 of the saddle bag. It was made by Nissin, and was labled LF RF RR LR.

[jaytee]

Wow.

 

Lots of vitriol on this board where these brakes are concerned.

 

I have to say, a lot of you guys sound down right religious in your hatred of a brake system that despite (because of?) its complexity - works.

 

Ok, I grant it might not be how you would have had your ideal brake system designed - so what?

 

They stop the bike just fine. Better than fine.

 

This seems truly a case of shut-up-and-ride.

 

JT

[Bob Palin]

They stop the bike just fine. Better than fine.

If that was true we wouldn't be complaining.