divanmostert
Registered user
Right on itTks, but when you look from the top of the bike, does the pedal stands inside or outside or right on the bash plate?
Anyhow, my pedal goes down to deep !!!
Rear brake...
- Thread starter ide508
- Start date
ide508
Registered user
Thanks for that 
Dean
Registered user
Mines booked in with the main dealer next Saturday will post the resulting solution. A loaner bike is booked if they give me one of thoes girlie F800GS's theres gonna be trouble 
similar problem recently on my 650, the rear brake was useless. Dealer rectified it by bleeding and refilling system and relieving me of £47 as "..it is not a warranty issue". To their credit they admitted they had no diea what had caused the problem and stated "Iif it happens again we shall contact BMW".
Not wishing to wait for the problem to re-occur I enquired with BMW via an e-mail as to what may have caused the issue. I was given a response over the 'phone of it being either too much off road riding aerating the brake fluid (it rarely ventures off road) or causing the brake fluid to boil due to excessive use (again not an option as the rear brake is rarely used and certainly not in anger).
I would be keen to learn of any other theory advanced by BMW representatives as to the possible cause of this problem.
Not wishing to wait for the problem to re-occur I enquired with BMW via an e-mail as to what may have caused the issue. I was given a response over the 'phone of it being either too much off road riding aerating the brake fluid (it rarely ventures off road) or causing the brake fluid to boil due to excessive use (again not an option as the rear brake is rarely used and certainly not in anger).
I would be keen to learn of any other theory advanced by BMW representatives as to the possible cause of this problem.
Greggers
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Here's a thought ....
The black 'thingie' on the top is a concertina type thingie, which is a special kind of thingie...
Remember that brake fluid doesn't like water or moisture? Actually it likes it a lot, brake fluid loves jolly old aitchtoowo so much that it takes every opportunity it can to 'ingest' as much of it as it possibly can.
In serious terms brake fluid is hygroscopic, in other words it will readily absorb water or moisture whenever it can. The problem that this water absorption causes is that the absorbed water has a much lower boiling point than the brake fluid, so as the brake caliper gets hot through friction the heat is transferred to the brake fluid, but the absorbed water in it will boil and produce bubbles of steam. Now, we all know that the hydraulic principle works on the basis that liquids are essentially incompressible, but we all also know that gas or vapour is compressible.... see where this is going? For the master cylinder (the brake lever end) to be able to actuate the slave cylinder (the caliper end) the fluid between the two pistons needs to be incompressible... but if there are bubbles of steam in the fluid, then these will compress very nicely thank you and will effectively accommodate the compressive volume of the master cylinder, vastly reducing the amount of force it can apply to the brake pads...
All understood so far? Good...
So, ignoring any bubbles for the moment, the master cylinder shunts fluid into the slave cylinder which in turn squeezes the pads onto the disc. However, the actual amount of fluid it shunts is really rather small, which is where the reservoir (the clear plastic tank by the brake lever) starts doing its job. As the pads wear down, then the slave cylinder pistons need to move further to accommodate this wear, but this needs more fluid to be introduced into the brake line - this fluid is contained ... yup, in the reservoir. Still with me? Ok, so we can all see that the fluid level in the reservoir goes down with time according to the wear rate of the pads. BUT, if the reservoir was fully sealed, the reduction in level would cause an effective vacuum in the reservoir which would suck the slave cylinder pistons back into the caliper - again reducing brake effort. This is where the black thingie comes into play. It's effectively a flexible seal, a very flexible seal which allows the fluid level in the reservoir to fall. The cap on the reservoir will have a breather to equalise the pressure, acting in exactly the same way as the breather vent on your petrol tank. So the concertina seal is protecting the brake fluid from the atmosphere - which contains a lot of water vapour which the brake fluid would love to absorb ....
The point I'm making is .... I wonder if there's an air-leak in the concertina seal...?
Greg.
The black 'thingie' on the top is a concertina type thingie, which is a special kind of thingie...
Remember that brake fluid doesn't like water or moisture? Actually it likes it a lot, brake fluid loves jolly old aitchtoowo so much that it takes every opportunity it can to 'ingest' as much of it as it possibly can.
In serious terms brake fluid is hygroscopic, in other words it will readily absorb water or moisture whenever it can. The problem that this water absorption causes is that the absorbed water has a much lower boiling point than the brake fluid, so as the brake caliper gets hot through friction the heat is transferred to the brake fluid, but the absorbed water in it will boil and produce bubbles of steam. Now, we all know that the hydraulic principle works on the basis that liquids are essentially incompressible, but we all also know that gas or vapour is compressible.... see where this is going? For the master cylinder (the brake lever end) to be able to actuate the slave cylinder (the caliper end) the fluid between the two pistons needs to be incompressible... but if there are bubbles of steam in the fluid, then these will compress very nicely thank you and will effectively accommodate the compressive volume of the master cylinder, vastly reducing the amount of force it can apply to the brake pads...
All understood so far? Good...
So, ignoring any bubbles for the moment, the master cylinder shunts fluid into the slave cylinder which in turn squeezes the pads onto the disc. However, the actual amount of fluid it shunts is really rather small, which is where the reservoir (the clear plastic tank by the brake lever) starts doing its job. As the pads wear down, then the slave cylinder pistons need to move further to accommodate this wear, but this needs more fluid to be introduced into the brake line - this fluid is contained ... yup, in the reservoir. Still with me? Ok, so we can all see that the fluid level in the reservoir goes down with time according to the wear rate of the pads. BUT, if the reservoir was fully sealed, the reduction in level would cause an effective vacuum in the reservoir which would suck the slave cylinder pistons back into the caliper - again reducing brake effort. This is where the black thingie comes into play. It's effectively a flexible seal, a very flexible seal which allows the fluid level in the reservoir to fall. The cap on the reservoir will have a breather to equalise the pressure, acting in exactly the same way as the breather vent on your petrol tank. So the concertina seal is protecting the brake fluid from the atmosphere - which contains a lot of water vapour which the brake fluid would love to absorb ....
The point I'm making is .... I wonder if there's an air-leak in the concertina seal...?
Greg.
Dean
Registered user
I had a similar problem when mine had about 2000 miles on it.The dealer flushed it through and bled it,no further problem.The dealer said some bikes do this and others don`tbut he didn`t know why.
Mines booked in with the main dealer next Saturday will post the resulting solution. A loaner bike is booked if they give me one of thoes girlie F800GS's theres gonna be trouble
Bike went in to main dealers today,
loan bike taken, fantastic bike I think it will be my next Bike ...one Day
Torque about a good ride, standard seat, screen and exhaust all good
a 60 plate with less than a 1000 miles on it it just felt right
Oh what fun 
anyhow my brake problem was solved as above a flush out of the old fluid and then replaced with new
the brake pedal is spot on. (to be honest i had got used to riding it and did not realise how bad it was) now its right where it should be.Main dealer said moniter it for a week or two any problems they will have it straight back, but all apears and should be ok so looks like it was the cure.
the charge for this work material and labour = Free of charge.
the charge for the loan bike = Free of Charge.
My main dealer I owe a big thank you
so thank you Cannon BMW in braintree, Essex
loyal customer Pete O Static
Registered user
Rear Brake Issue
Greetings from Canada.
I have had my 800GS now for just over two years. Very early on, I too noticed that my rear brake pedal seemed to be out of adjustment because I felt there was too much travel before the actual braking started. I made a small adjustment by adjusting the plunger / actuator at the back of the pedal. All seemed great until about 15kms down the road, the brake seized on and over heated my rotor.
Took it to the dealer with my tail between my legs and they "fixed" it all up. The brake seized again on the way home. Dealer fixed it again but with an excessive amount of freeplay back in the pedal.
After all this, I tolerated the extra travel in the brake pedal with the adjuster backed off enough to ensure that I did not get another recurrence. However,
due to other various unrelated servicing issues, I stopped taking my bike back to the dealer from which it was purchased and instead, took it to another dealer in our area for servicing. He found a host of issues that had not been addressed properly in the past. When I got the bike back, it was absolutely beautiful. It has never run so well. I also noticed right away that the excessive play in my rear brake pedal was gone! It was adjusted exactly how I wanted it and no rear brake seizure issues! A few weeks later, I asked the technician what he had done and he explained to me that regular brake fluid flushing ( annually ) was imperative with this bike ( particularly if you ride off road ) and that the ABS pump system requires a special BMW tool ( which not all BMW dealers have apparently ) to to the job properly. He suspected that the brake service had not been done properly in the past. He asked me whether or not I had ever felt what could be best described as " Hydraulic Feedback" or a very short burst of pulsations felt in the front brake lever with initial brake application. I explained that yes, I had indeed experienced that very very infrequently, maybe three times total and that I had informed my dealer of it. He explained that the issues were related and it would no longer happen and so far, it has not! Due to professional courtesy, he didn't come right out and say that the last dealer had totally botched the brake servicing but it was easy to read between the lines and see that he was not at all impressed with whomever had been servicing my bike in the past.
So what I learned was that brake fluid flushes are very important on this bike, more frequent than any other bike I have owned and that if it is not done correctly, some of the old fluid remains in the pump and causes "air" issues.
In Canada, at least where I live, there is apparently a shortage of "qualified" BMW techs. I was amazed to learn that not all of the BMW dealers have BMW master techs on staff. In the Toronto area, we have four BMW dealers with one dealer in particular doing the majority of the motorrad service work. This is where I got everything with my bike "put right".
Not sure if you have the same issue in the UK but it may pay to ask just "who" is working on your bike next time. Since my last brake service, I have put on about 8000 kms with no excessive freeplay on the brake pedal and all is good.
Greetings from Canada.
I have had my 800GS now for just over two years. Very early on, I too noticed that my rear brake pedal seemed to be out of adjustment because I felt there was too much travel before the actual braking started. I made a small adjustment by adjusting the plunger / actuator at the back of the pedal. All seemed great until about 15kms down the road, the brake seized on and over heated my rotor.
Took it to the dealer with my tail between my legs and they "fixed" it all up. The brake seized again on the way home. Dealer fixed it again but with an excessive amount of freeplay back in the pedal.
After all this, I tolerated the extra travel in the brake pedal with the adjuster backed off enough to ensure that I did not get another recurrence. However,
due to other various unrelated servicing issues, I stopped taking my bike back to the dealer from which it was purchased and instead, took it to another dealer in our area for servicing. He found a host of issues that had not been addressed properly in the past. When I got the bike back, it was absolutely beautiful. It has never run so well. I also noticed right away that the excessive play in my rear brake pedal was gone! It was adjusted exactly how I wanted it and no rear brake seizure issues! A few weeks later, I asked the technician what he had done and he explained to me that regular brake fluid flushing ( annually ) was imperative with this bike ( particularly if you ride off road ) and that the ABS pump system requires a special BMW tool ( which not all BMW dealers have apparently ) to to the job properly. He suspected that the brake service had not been done properly in the past. He asked me whether or not I had ever felt what could be best described as " Hydraulic Feedback" or a very short burst of pulsations felt in the front brake lever with initial brake application. I explained that yes, I had indeed experienced that very very infrequently, maybe three times total and that I had informed my dealer of it. He explained that the issues were related and it would no longer happen and so far, it has not! Due to professional courtesy, he didn't come right out and say that the last dealer had totally botched the brake servicing but it was easy to read between the lines and see that he was not at all impressed with whomever had been servicing my bike in the past.
So what I learned was that brake fluid flushes are very important on this bike, more frequent than any other bike I have owned and that if it is not done correctly, some of the old fluid remains in the pump and causes "air" issues.
In Canada, at least where I live, there is apparently a shortage of "qualified" BMW techs. I was amazed to learn that not all of the BMW dealers have BMW master techs on staff. In the Toronto area, we have four BMW dealers with one dealer in particular doing the majority of the motorrad service work. This is where I got everything with my bike "put right".
Not sure if you have the same issue in the UK but it may pay to ask just "who" is working on your bike next time. Since my last brake service, I have put on about 8000 kms with no excessive freeplay on the brake pedal and all is good.
Last edited:
Dean
Registered user
well all what was said is that its all as it should be, they changed the fluid I asked how much I owe them the reply was nothing
But I imagine by other peoples posts above, that this was a large chunk of good will if you see my post 15 above about them also changing rear rotor/brake disc and pads was 20th February this year 2010. (also free of charge). So a good 8 month Gap from the last tinkering with my rear brake.
I think the problem that i had carried for a long period had tried to be adjusted out in the past . but the cure was the fluid change, but I dont think they was oblidged to do a free of charge and I was not expecting it
. As for my warranty it expired at the end of September. But its OK as I have another 
chas820
Registered user
My "repair" was free as well plus a loan bike.Thank you VINES
ide508
Registered user
Hi Bernard, I have the same problemI would say if you look at the bike and the rear brake pedal is at 3 O clock when not used then it feels like 5 or 6 before I get a result.
I have mentioned it to my main Dealer first time the adjusted so fine that the rear slowly seazed up in the dark the rear disc was glowin like a UFO bright orange. the dealer collected my bike and i insisted they change the rear pads and disc FOC which they did and returned the bike.
It has been back for a service since and I mentioned the extra travel and they felt all was OK.
It apears to again have to much un adjustable free play so it will go back to the dealer for them to sort pretty soon. Its like a lot of things when they gradualy get worse you do not seem to notice.
I use my rear brake quite a bit. so if you get yours figured out post up please
the solution.
personaly I think its a pressure of fluid problem but for what reason
Hi Dean,and everybody...
Well it took a loooong time to answer, got used/lazy to ride with almost no rear brake until the time that I've decide that it's enough
The answer to my problem was a very very easy fix! In fact you all are able to tighten or loosen the rear brake pedal.
You just need to unscrew the bold that is on that vertical "thing" on the left side of the pedal.
A friend of mine working for BMW (car dept) came last night and settle this for me.
Now I have real rear brake again an though I'm not using it too much, it's good to know that it's available when necessary.
Hope my English was good enough for you to understand
By the way, I haven't rode the bike for four months
but she was hooked to a BMW charger.It started very easily and I have nothing to report except that it's like new now
Cheers everybody
ronecc
Registered user
Hello ide508.
I know I am late asking this, and it has nothing to do with your brakes. I have just got an 800GS, and was looking for a bigger screen. Yours looks good, with cut outs for hand guards and the spoiler on the front. Could you tell me what make it is and does it work for your height. I am 6'2".
Thanks
I know I am late asking this, and it has nothing to do with your brakes. I have just got an 800GS, and was looking for a bigger screen. Yours looks good, with cut outs for hand guards and the spoiler on the front. Could you tell me what make it is and does it work for your height. I am 6'2".
Thanks
ide508
Registered user
Hey ronecc
The screen is Touratech high screen with on top of it an MRA spoiler.
It does work great, at least for me, no problems at all with the hand guards...
I'm 1.83m which is for you 6'.1" and I can ride visor up till 80 km/h.
Enjoy you're bike
The screen is Touratech high screen with on top of it an MRA spoiler.
It does work great, at least for me, no problems at all with the hand guards...
I'm 1.83m which is for you 6'.1" and I can ride visor up till 80 km/h.
Enjoy you're bike
skywalker
Guest
They don't look as new, but I think that they are still thick enough.
Don't know if this help?
Cheers
Jesus - looking at the state of that brake caliper I'm surprised you've got a brake at all.
That's never been cleaned in a million years - you just have to look at all the salt corrosion thats evident every where in that picture.
Its attacked the pad material, the caliper itself, the caliper hanger, spokes etc.
Really does make you wonder what the rest of the bike's like.
Have a look a Micky's bike on this site - lives outside ,done over 58k & still looks like new.
A serious overhaul looks like its reqd & a crash course in looking after a bike .
Jesus - looking at the state of that brake caliper I'm surprised you've got a brake at all..
However, he has got a great camera. Nice detailed pic.
skywalker
Guest
Just showing lads the picture at work. Wonder what type of lens he's using.
ide508
Registered user
Trust me, my rear brake is working perfectly now!
Boy, it looks like you have never ride in the rain on a sandy rural environment... that's were I live
Also, it seems that you confuse sand and corrosion
My bike has never been ridden on salted road and there is no corrosion at all, nowhere !Usually it looks like the pictures below, feel free to zoom on the second picture
I have seen Micky's bike and mine is nicer cause grey
Bla bla blaA serious overhaul looks like its reqd & a crash course in looking after a bike .
Aren't you suppose to work "at work" ?
After reading all the posts i would say the rear master cylinder on the early bikes may have suffered with seal issues and let moisture in ?
If changing the fluid fixes it (normally a 2 yr mtx job) either it has a bad seal somewhere or the fluid is shite.
Only problem on mine brake wise was far too much grease on the back of the front pads, it got everywhere.
Hate to admit but that silver one looks nice
If changing the fluid fixes it (normally a 2 yr mtx job) either it has a bad seal somewhere or the fluid is shite
.Only problem on mine brake wise was far too much grease on the back of the front pads, it got everywhere.
Hate to admit but that silver one looks nice
ide508
Registered user
Well, perhaps but I had my problem fixed as I said just by playing a little with the adjustment bold.
No more problems, like new
Cheers
Bernard
No more problems, like new
Cheers
Bernard
skywalker
Guest
Bikes always look clean when you photograph them from that distance !!
How about some close ups like the brake caliper shot ?
The fact remains you came on here to get advice about your back brake problem and didn't like the reply.
Fact remains wether your brake works now or not, is the state your brake caliper is in.
There is no excuse where ever you live to let such a vital component get into that state.
How about some close ups like the brake caliper shot ?
The fact remains you came on here to get advice about your back brake problem and didn't like the reply.
Fact remains wether your brake works now or not, is the state your brake caliper is in.
There is no excuse where ever you live to let such a vital component get into that state.
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