Servo Failures: DRIVERS' PERCEPTION OF SECONDARY BRAKING SYSTEMS

[mikeh501]

The only thing I would say is that if this unsubstantiated bollocks about brake failure catches on to the wider public and it hurts my residual, I for one will be well pi$$ed

All the poster keeps on about is servo this and ABS that. No facts. No mass of owners reporting brake failure. This is all just conjecture. I have trouble thinking what the agenda is here. It just feel like spam to me, no substance to any of it.

The brakes on my 04 servo'd ABS adventure are excellent, thats it. Maybe they are more complicated than normal brakes, but they sure as hell stop better than my Aprilia which had gold series brembos when two up and luggage.

 

[(RIP) Dennis]

The brakes on my 04 servo'd ABS adventure are excellent

Yes, they certainly stop the bike, but what they lack is feel. To an inexperinced rider, use of the front brake at fairly slow speed can be positively dangerous.......and they are not any better or quicker at stopping the bike on my servo/abs 03 ADV than on my non servo, abs 00 GS - just more complicated - more expensive - more to go wrong.

 

[Steptoe]

The only thing I would say is that if this unsubstantiated bollocks about brake failure catches on to the wider public and it hurts my residual, I for one will be well pi$$ed

.

not as pissed as you would be if your brakes went U/S -


They are having problems with the ELECTRIC servo . As some motoring journalist have commented on .

The fact that you and lots of others haven't, doesn't mean there isn't a problem .

If/ when the problems are found/cured, the residuals on your bike will be better than a non-servo

 

[JohnnyBoxer]

Maybe the extra pressure from the servos is required due to the ABS?

I honestly don't know - as you say there are plenty of non servo bikes out there with perfectly adequate brakes.

BMW GS and GSA Bikes up to MY 2003 didn't have servo to operate their ABS.........so....... er...........no a Servo is not needed to operate ABS

 

[JohnnyBoxer]

Yes, they certainly stop the bike, but what they lack is feel. To an inexperinced rider, use of the front brake at fairly slow speed can be positively dangerous.......and they are not any better or quicker at stopping the bike on my servo/abs 03 ADV than on my non servo, abs 00 GS - just more complicated - more expensive - more to go wrong.

Well said Dennis, my thoughts exactly ..............my 1997 R1100GS with ABS (but no servo) had perfectly adequate brakes and the improvements on my 2002 GS1150 non Servo ABS Evo brakes were stunning.

However the brakes on my 2004 1150GS with Servo ABS...... stop no quicker ......
BUT they lack feel and feedback compared to the 2002 GS brakes and all this has been caused by introducing a servo.

 

[Arthurwg]

When I experienced "brake failure" at 85mph on th highway there was virtually no residual braking available. The cause of the failure was determined to be a loose ground wire at the battery. I wonder if this example produced less residual braking than other brake failures?

 

[laughingBob]

Understood Bob. The point I struggle with is illustrated by your post:

The servo on a bike where it's fitted only makes braking easier, it doesn't increase braking efficiency, so as long as you squeeze the brake lever enough you'll stop as quickly as you would if the servo were working.

So why make a servo in the first place? If there had been a stream of posts complaining that the brakes on oilheads had been crap, the stopping distances too long, the effort required at the lever excessive etc, I could understand the need to fix it. The fact is, my Adv has the most efficient brakes I've used on a BMW - loads of feel, easy pull on the lever plus enough power to lock either wheel - why change that for something that is no more efficient?

Maybe I'm chasing my tail on this one, but I really can't see this as a great leap forward - just complexity for its own sake...

Mike

Well if the ABS isn't the reason for the servo I don't know why it has one but, it does. It certainly seems like an overly complicated system but I haven't had any problems with mine and to be honest as long as I know I can stop within the same distance, whether it's working or not, in an emergency I'm not too bothered. There seem to be very few reported faults with them in any case.

 

[Arthurwg]

My brake failure was DOCUMENTED when the bike's computer was downloaded. It showed multiple brake failure codes, so many in fact that the cause couldn't be diagnosed from that information. Someone at BMW headquarters here in the states suggested that the service tech check the ground wire to the battery. That was it, apparently. The point is, a loose ground wire shouldn't result in death. I consider this to be a serious design fault. Thankfully there was very little trafic on the road at the time and no need to stop quickly. I consider myself lucky to be alive.

 

[JohnnyBoxer]

My brake failure was DOCUMENTED when the bike's computer was downloaded. It showed multiple brake failure codes, so many in fact that the cause couldn't be diagnosed from that information. Someone at BMW headquarters here in the states suggested that the service tech check the ground wire to the battery. That was it, apparently. The point is, a loose ground wire shouldn't result in death. I consider this to be a serious design fault. Thankfully there was very little trafic on the road at the time and no need to stop quickly. I consider myself lucky to be alive.

LISTEN TO THIS MAN !!!!!!!!!!!!!!!

This is his true experience.............it is NOT hearsay..............his ELECTRIC Servo failed due a loose earthing wire connection and there was no residual braking power @ 85mph............!!!!!!!!!!

Why are the doubters.......... saying there are no recorded cases and it's all conjecture and hearsay.................
This is one and I personally know of at least one other locally and he's a Board member too.

 

[[email protected]]

LISTEN TO THIS MAN !!!!!!!!!!!!!!!

This is his true experience.............it is NOT hearsay..............his ELECTRIC Servo failed due a loose earthing wire connection and there was no residual braking power @ 85mph............!!!!!!!!!!

Why are the doubters.......... saying there are no recorded cases and it's all conjecture and hearsay.................
This is one and I personally know of at least one other locally and he's a Board member too.

hello together!

this here is the documentation of a servo brake failure in Germany on 6th of august in the year 2004 on a BMW R1150GS Adventure 03 (# WB10441A74ZH59720).



Please keep in mind the essence of the Article in DIE WELT: There have been a detection of 21 irregular function. Furthermore there where hundred of cases of (the computer) logging some incident which went undetected by the rider or, where noted by the rider but 'Not' logged by the computer. This is what BMW admits.

Around this forum, around UKGS and especially in Germany at the Beemer-boards there are lots of first hand reports about servo brake failures. Furthermore there are reports about the 'ice patch effect' and weird phenomenons, especially with the servo brakes on big BMW LT motorbikes.

I do personally know riders with brake problems.

OH

 

[[email protected]]

OT: Complaints in the states

Off Topic: Complaints about ABS-Design (no servo failure):

 

[Dave Barrett]

OH,

Where did the above info come from? Whoever wrote them certainly has never heard of the TREAD Act!

 

[Engineer]

If I am correct in the assumption that it is possible to have ABS without servo assistance, then why do BMW add servo assistance? I can see no benefit at all, it is just something else to go wrong - or have I missed something?

I have been searching the Internet for reliable technical information on how the various ABS/SERVO systems work but cannot find and really good technical info on any of the manufacturers websites.

Will

 

[Dave Barrett]

To try and answer the above:

Yes, it is possible to have ABS with Servo assistance. From a technical viewpoint the two systems are independent of one another - the ABS to stop the wheels locking (as we all know), whilst the servo provides brake assistance, meaning less physical effort is required to apply a specific brake force.

Why to BMW add the servo? Good question, since to date they are the only bike manufacturer with this system (However, ALL car manufacturers have servo's in the braking system).

My guess is that this will be legislation in the very near future. I don't think that a manufacturer the size of BMW will just decide that it's a good idea and then install it. Today, all manufacturers are looking to save costs, not add them.

As I mentioned above, the servo just increases the amount of braking force applied to the brake pads. In the BMW system, when the brake lever is applied, an electrical servo (pump) is started up, which increases the brake pressure to the calipers in relationship to the hand pressure applied at the lever.

Most car systems are vacuum operated, but they have exactly the same effect, just that you don't hear an electrical pump starting up.

I hope that helps...

 

[(RIP) Dennis]

Dave, whilst I understand the supposed benefits of a Servo. Surely a vacuum operated one as use by the car manufacturers for many,many years, must be more reliable than an electical item as it lacks the number of wear prone moving parts. Is it a weight saving route ?

 

[John Armstrong]

And how is the vacuum generated for a servo? By the intake depression, which is ok on carburettor motors, but becomes more problematical on diesel / injected motors.

On diesel cars that I've had, the servo vacuum has been generated by an engine driven pump, which must be increasing the power losses as it's always running? So, an answer surely is to have the pump running only when needed?

 

[Dave Barrett]

Dennis:

In fact the opposite is true - the electrical version has less moving parts, and should in theory be more reliable (from a durability point of view). It will for sure weigh less as well. Another thing to consider is that the vacuum operated versions need fairly large diaphragms to operate well, which would be rather difficult to hide away on a bike.

John:

On fuel-injected petrol engines, there is still sufficient vacuum behind the throttle butterflies to drive the servo.

As you say, all diesel engines have an engine-driven vacuum pump, normally either on the end of the alternator or alternatively a specific pump. As you correctly state, since they are running all the time, they absorb power (albeit only a little in the scale of things). This could also be judged as another advantage of an electric version, since it starts up only when the brake lever is operated.

 

[Arthurwg]

An electric servo system might be fine, as long as the electricity keeps flowing. But can BMW guarantee that? If not, the system should have an adequate hydraulic back-up. Unfortunately, my R1200GS doesn't have that.

 

[Engineer]

To try and answer the above:

Yes, it is possible to have ABS with Servo assistance. From a technical viewpoint the two systems are independent of one another - the ABS to stop the wheels locking (as we all know), whilst the servo provides brake assistance, meaning less physical effort is required to apply a specific brake force.

Why to BMW add the servo? Good question, since to date they are the only bike manufacturer with this system (However, ALL car manufacturers have servo's in the braking system).

My guess is that this will be legislation in the very near future. I don't think that a manufacturer the size of BMW will just decide that it's a good idea and then install it. Today, all manufacturers are looking to save costs, not add them.

As I mentioned above, the servo just increases the amount of braking force applied to the brake pads. In the BMW system, when the brake lever is applied, an electrical servo (pump) is started up, which increases the brake pressure to the calipers in relationship to the hand pressure applied at the lever.

Most car systems are vacuum operated, but they have exactly the same effect, just that you don't hear an electrical pump starting up.

I hope that helps...

Thanks Dave that is helpful - my feeling is that extra braking force is not required on a motorcyle as modern motorcycle disc brakes can lock the wheels easily anyway, so I don't believe that we need a system that creates an even greater braking force.

I guess that a servo would help if the rider had some sort of manual disability that stopped them from applying the 'normal' level of force to the brake lever, but this is the only situation that I can imagine where a servo would be needed.

Will

 

[bigkuri]

All these world-wide dicussions on servo's - why cannot unhappy owners simply buy some new brakes lines and bypass the whole lot? I know that this would also get rid of ABS, but if some are so concerned about it, then why not?

Could then either remove the ABS/servo unit and lines, or potentially even just disconnect and blank off the input/output lines.

Have looked at this myself in passing interest - and from a thread in AdvRider it should be possible to do. As far as I can tell all the master cylinder pistons are the same, likewise the other "manual" braking components.

The result should be pure simply manual brakes?