I'm currently on a mini-tour round the Alps. Yesterday morning while coming down a poorly-surfaced road, I discovered I had no rear brake authority at all. No immediate harm done, so once we were off the mountain I headed off to the nearest motorrad dealer (Bayard Moto in Gap), a not unpleasant 50m ride to the west. Given that I arrived at 4.30 on a Friday afternoon, they couldn't have been more helpful - the tech replaced the rear brake fluid, and his explanation was that repeated use of front brake only causes air to build up in the rear brake system. This would make sense in that virtually all of my miles are road miles and given the linked brakes, I rarely use the rear brake lever - but how can this actually happen? ie how can air somehow get sucked into the rear brake system? Bike has done about 14k miles, serviced on schedule with front pads in Feb and brake fluids changed in Nov last year. Anyone ever heard of this?
2016 GSA rear brake failure
- Thread starter jtb
- Start date
Hearing more and more about rear brakes. I have a March 17 LC GSA. I was told it required new rear pads ar 3000 miles and again at 6000. I’ve done another 3000 miles since the annual service and it’s just been checked again. The rear disk is “on its minimum limit” and the rear pads are 60% worn. - there’s also a small hole in the rubber drive gaiter that’s just in front of the rear axle, the centre and side stands have more corrosion than my 100000mile pan European had and there is bubbling in the paint at several points around the engine.
I’m waiting for Bahnstormer to contact me - in fact, I’m about to send them a “WTF is happening?” Email.
Like you, I rarely activate the rear brake.
I’m waiting for Bahnstormer to contact me - in fact, I’m about to send them a “WTF is happening?” Email.
Like you, I rarely activate the rear brake.
No comment on the brake fluid issue but I have had 3 GS LC, 14k miles on each of the first two and 4.5k on the third and I have never had rear brake pads? I ride 90% 2 up and rarely use the rear brake 
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Sent from my iPhone using Tapatalk
Are you sure something didn't get lost in translation?
Most brake problems in the mountains are caused by us trailing the rear brake & overheating the brake fluid/pads/disc, indeed the linking of the system probably doesn't help either. Frankly it's easily done, especially if 2-up with luggage, trying to give the pillion a reasonably comfy ride. Symptoms are the pedal biting point slowly going away, getting ever longer, until nothing happening whatsoever. The simple cure is just to stop & let the whole shooting match cool off. Then, when possible, it's a good idea to change of fluid - effectively what has happened in the OPs case. OK there may have been a little air present, I have seen it before with a brand new bike, but I rather doubt it was the primary cause.
Incidentally, I am often amazed how many BMWs I see, showing clean almost clear brake fluid up front, but turgid brown fluid in the rear reservoir. Always worth checking, although you can never counter the clown that just changes the reservoir fluids with a turkey baster, but that's another story.
Most brake problems in the mountains are caused by us trailing the rear brake & overheating the brake fluid/pads/disc, indeed the linking of the system probably doesn't help either. Frankly it's easily done, especially if 2-up with luggage, trying to give the pillion a reasonably comfy ride. Symptoms are the pedal biting point slowly going away, getting ever longer, until nothing happening whatsoever. The simple cure is just to stop & let the whole shooting match cool off. Then, when possible, it's a good idea to change of fluid - effectively what has happened in the OPs case. OK there may have been a little air present, I have seen it before with a brand new bike, but I rather doubt it was the primary cause.
Incidentally, I am often amazed how many BMWs I see, showing clean almost clear brake fluid up front, but turgid brown fluid in the rear reservoir. Always worth checking, although you can never counter the clown that just changes the reservoir fluids with a turkey baster, but that's another story.
Thanks for this but I am 100% certain that I understood the explanation from the tech. Riding solo, not much luggage, no rear brake trailing going on, and perhaps most relevantly to your hypotheses, this was a very slow trip because of the road surface, immediately after a lunch stop - so the bike was not hot.
Don't forget you trail the rear, effectively, when using the front on these linked systems. Anyway if it aint boiling brake fluid, the air had to find it's way in somehow.
Have you checked carefully the rear brake lines. I have known road debris flung up from the rear tyre make the tiniest pinhole in a brake line, witnessed only by what looked like a small blob of tar on the line. This was sufficient to admit air to the system, but wasn't large enough to allow any significant fluid to escape; well not until I picked at it that is. I could never get the thing to bleed clean & the pedal would drop slowly during a ride, yet would pump back up when used frequently. Otherwise could be the rear master seals, but seems less likely ivo the age/mileage of your bike.
Anyway, just a thought. Take care, maybe get your dealer to double check everything when you get back home.
I’ve got a 2017 Rallye that’s in for its 12k service Tuesday. Rear brake has been an unused appliance for the past 100 miles as to get any pressure I’ve got to get the lever to the 45 degree point. I’m sure Vines will fix it.
fred_jb
Registered user
Mine had a lot of movement from new, maybe not 45 degrees, but I wasn't very happy with it. However, after the 6000 mile service where the brake fluid is changed it was much much better and is now quite acceptable.
That's an interesting thought. I am now back in the UK (flew back tonight) so I can't try this inspection until I go back in a couple of weeks to carry on with the mini tour - but I'll definitely have a good look as suggested. Bike will go back to Chandlers for a proper check over when it comes back to the UK next month.
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It is more of a common problem that you think.
http://advrider.com/index.php?threads/bmw-r1200gs-lc-rear-brake-failures.1264712/
Interesting point from advider below.
For all of you who are having to bleed the rear brakes every few months....have any of you had the rear master cylinder replaced?
There were several threads here where someone mentioned that Brembo rear master cylinders were the culprit, and were periodically letting in a big gulp of air. Something about the wrong seal on the piston, or such.
It was noted too that other bikes using this rear master had the same problems, such as Ducati Multis, Guzzis, Aprillias.
What I can't find is where anyone said BMW recognized it was a bad batch of master cylinders and issued a recall or service bulletin. I think what happened is that dealers just replaced MCs on bikes under warranty if they had to be bled frequently.
So, if you haven't had your MC replaced, I'd go that route first.
http://advrider.com/index.php?threads/bmw-r1200gs-lc-rear-brake-failures.1264712/
Interesting point from advider below.
For all of you who are having to bleed the rear brakes every few months....have any of you had the rear master cylinder replaced?
There were several threads here where someone mentioned that Brembo rear master cylinders were the culprit, and were periodically letting in a big gulp of air. Something about the wrong seal on the piston, or such.
It was noted too that other bikes using this rear master had the same problems, such as Ducati Multis, Guzzis, Aprillias.
What I can't find is where anyone said BMW recognized it was a bad batch of master cylinders and issued a recall or service bulletin. I think what happened is that dealers just replaced MCs on bikes under warranty if they had to be bled frequently.
So, if you haven't had your MC replaced, I'd go that route first.
Thought provoking thread.
I’ve owned a single cam , twin cam and now an LC r1200gsa. All of them have rear brakes that are different to most other bike that I’ve experienced. On those - for example Suzuki gsx1400, the brake pedal is adjustable for height and the feel is near instant - 5mm travel then hard pressure. Stomp firmly with the clutch disengaged and the rear wheel locks every time.
Same thing with my f800gs - abs not withstanding.
None of my r1200gs bikes have had responsive rear brakes and the lack of pedal height adjustment on any of them has led to me hardly ever bothering to use the rear brake while riding on the road.
Most other bikes in my experience have a directly linked push rod that has a threaded end into clevis pin on the lever end and the piston in the master cylinder on the other end. For some reason, r1200gs/a has a set up where the push rod ends in a rounded pin that pushes onto the piston. There is a adjustable gap between the two. The different set up makes me think that the gap is to allow for fluid expansion in the abs unit sitting atop the engine. If one reduces the gap, as I’ve tried, looking to reduce the lever travel before the brake bites, then the brake starts to drag after a while ( when warmed up).
I don’t know the answer to this and simply live with it accepting that the rear brake lever is good for holding the bike while stationary but not much else. The linked brakes set up works well on the road so for me it’s an enigma rather than a major problem.
Alan R
I’ve owned a single cam , twin cam and now an LC r1200gsa. All of them have rear brakes that are different to most other bike that I’ve experienced. On those - for example Suzuki gsx1400, the brake pedal is adjustable for height and the feel is near instant - 5mm travel then hard pressure. Stomp firmly with the clutch disengaged and the rear wheel locks every time.
Same thing with my f800gs - abs not withstanding.
None of my r1200gs bikes have had responsive rear brakes and the lack of pedal height adjustment on any of them has led to me hardly ever bothering to use the rear brake while riding on the road.
Most other bikes in my experience have a directly linked push rod that has a threaded end into clevis pin on the lever end and the piston in the master cylinder on the other end. For some reason, r1200gs/a has a set up where the push rod ends in a rounded pin that pushes onto the piston. There is a adjustable gap between the two. The different set up makes me think that the gap is to allow for fluid expansion in the abs unit sitting atop the engine. If one reduces the gap, as I’ve tried, looking to reduce the lever travel before the brake bites, then the brake starts to drag after a while ( when warmed up).
I don’t know the answer to this and simply live with it accepting that the rear brake lever is good for holding the bike while stationary but not much else. The linked brakes set up works well on the road so for me it’s an enigma rather than a major problem.
Alan R
Victor c
Registered user
I’ve just had a similar experience whilst on tour, only really use the rear brake for slow speed stability assistance.
Steady ride through UK, France and Germany to reach Garmisch, then 2 days later headed into Austria and Italy. Noticed excessive travel in my rear brake pedal when leaving Garmisch, but still had braking effect.
Come to tackle the mighty Stelivio (North to South), only to find the rear brake was almost non existent. Fluid level ok and plenty of meat on the pads. That evening, decided to strap down the pedal and leave it over night, which resulted in a better pedal action, but still not perfect. This remained the same for the rest of the trip.
Fast forward to my return, and cleaning the bike this morning, decided to flush some fresh fluid through the rear brake system (old fashioned way of pumping it through with the pedal). This has returned the pedal travel to as it should be. It is hard to say if much air was in there, but it is definitely a concern.
Will make a determined effort to you the rear brake more now.
Mark
The integral brakes are designed in such a way that when you use the handbrake the rear comes slightly on and stabilizes the bike.
If you go easy on the brakes pretty much all the stopping is performed with the rear brake, thus the heavy wear on rear compared to the front for may of us.
If you go easy on the brakes pretty much all the stopping is performed with the rear brake, thus the heavy wear on rear compared to the front for may of us.
Yep that's all understood - but isn't in any way relevant to the problem of total rear brake failure.
Anyway - small update: BMW GB have acknowledged that this is a known problem, although they are less clear on the root cause. My GSA came back to the UK a week or so ago and is in with the dealers in a week's time for further investigation.
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