r850r front brake problem

[motormount]

Good evening,

I exchanged my TTR600E for an R850R.

The bike had been stationary in a closed space for about 15 years.
We did a basic service — oil, filters, etc. — replaced the fuel lines, put on new tires, and I took it out for a ride, but the front wheel was almost stuck.
I replaced the brake pads, and the situation improved significantly, but not completely — I thought maybe the pads hadn’t seated properly.
I took it out again, and after about a kilometer, the brake hoses burst.
I replaced the hoses and noticed a small improvement in the front wheel again, but it still wasn't moving freely.
(I was checking the movement of the front wheel with the bike stopped and on the center stand — while riding, I didn’t notice any issue.)
After two days, brake fluid started leaking from underneath the brake fluid reservoir.
I replaced the reservoir piston, and now the brake lever feels much better, but the front wheel is still “sticking.”
It has improved a bit more, but it still sticks.
When the bike is on the center stand, I have to use some force to rotate the front wheel.
Also, once I stop rotating it, it stays in place — it doesn’t spin even half a centimeter on it's own.

I really love the easy handling of the bike, when you move, even in medium city traffic, you can't feel it's weight, and i also cannot feel the brake problem, but i know it's there, and i can't trust it to go for an open road ride.

All 4 front pads seems like to be in constant ''touch'' with the disc when you look at them, but the bike moves '' normal ''.

I can pm, mail, or upload photos of the pads and the braking disk, with the bike stopped if you like.

Any ideas?

What should i look for?

Thanks in advance!

 

[Neil W]

Put it on the centre stand and unbolt the calipers and hang them out of the way , if the wheel spins freely with the calipers out of the way it is the calipers causing your issue .
Bought a low mileage r1150gs a few years ago and the lever had a dead feel and needed a hard pull to apply the brakes and then they did very little to stop the bike but caused the wheel to be difficult to turn by hand .
Did the fluid change and replaced the brake lines with Goodridge but it needed the calipers rebuilding using new seals and piston before the issue was addressed (the pistons were all partially seized in the caliper bores)

 

[Nick Marshall]

Just typed something very similar. Now deleted.

 

[Steptoe]

Which brake hoses burst ?
Did you replace all the front hoses ?

 

[motormount]

Put it on the centre stand and unbolt the calipers and hang them out of the way , if the wheel spins freely with the calipers out of the way it is the calipers causing your issue .
Bought a low mileage r1150gs a few years ago and the lever had a dead feel and needed a hard pull to apply the brakes and then they did very little to stop the bike but caused the wheel to be difficult to turn by hand .
Did the fluid change and replaced the brake lines with Goodridge but it needed the calipers rebuilding using new seals and piston before the issue was addressed (the pistons were all partially seized in the caliper bores)

Thanks Neil, i'll give it a try!

 

[motormount]

Which brake hoses burst ?
Did you replace all the front hoses ?

Yes the front ones!

 

[Steptoe]

Yes the front ones!

Upper and lower, all the flexible hoses ?

Have you retracted the caliper pistons making sure they aren’t sticking

 

[Riceburner]

Guaranteed sticking calipers. As said, strip clean and rebuild.

 

[motormount]

Upper and lower, all the flexible hoses ?

Have you retracted the caliper pistons making sure they aren’t sticking

upper and lower, all the way from the brake fluid reservoir to the calipers.

Must say though, piston calipers weren't sticking at all.
- checked when i change the hoses, not after replacing the brake fluid reservoir piston -

 

[motormount]

Good morning everyone and have a great week!


We removed the calipers again, cleaned them, but the wheel still sticks.


The pistons don’t fully retract, and the wheel turns with difficulty.


We tested the calipers one by one — the right caliper sticks more than the left one.


I found an old right caliper, cleaned it, and the situation improved slightly. I'm waiting this week for a friend who has a pair of calipers we know are working properly, and then I’ll find out whether it’s indeed a caliper issue (as I hope), or something else.


If I test those and it's not the calipers, what else could it be?


I thought about the ABS unit.


I’m considering sending the brake lines directly to the calipers, bypassing the ABS unit.


I believe many people have removed ABS, especially on the later models with servo brakes, but as far as I know, models like mine didn’t have issues with ABS — so I’d like to keep it.


Also, I did a deliberate hard brake once, and the ABS worked fine.


What do you think about that?


Then I thought about the brake reservoir.


I replaced the piston, but when you press the lever, brake fluid spurts out forcefully from the small return hole.


Does that indicate poor bleeding?


Lastly — and less likely — I noticed that the left brake disc has quite a bit of play in its floating bushings.


As I said earlier, testing the calipers one at a time showed the right one has the more serious issue — I’m just mentioning this in case it sparks any ideas.


One last thing: as I mentioned before, I changed the brake lines.


The OEM setup had a bridge/connection from the right disc to the left.


Now I’m sending a separate brake line to each caliper directly.


Could that cause any issues?


Thanks in advance for your time!

 

[Paul Young]

The brake lines can break down internally, especially if they are the original rubber ones. This creates a one way valve that allows fluid to push the pistons, but not to return. If the brake lines are new or stainless, this is less likely than the usual problem being that the calipers just need a thorough disassembly and service.

 

[OldCroc]

I had a 1150R. Had new tyres put on and then left on a trip. Only realised msny miles later that the front brakes were sticking. Bike only had 5 k miles on it. Tried a few of the usual things to release the brakes then was told by another biker with the same bike to try this. Loosen front wheel, take bike off the stand with loose front wheel. Hold front brake lever and put weight on front wheel through steering. Release brake lever. Re-tighten front wheel with the wheel still on the ground. Do NOT put it back on the stand first.
This is much easier if you have someone to help.
Hey presto - no more sticking brakes. Had the bike for another 30k and used the same procedure every time when changing front tyre. Dont ask me how ….

 

[motormount]

I had a 1150R. Had new tyres put on and then left on a trip. Only realised msny miles later that the front brakes were sticking. Bike only had 5 k miles on it. Tried a few of the usual things to release the brakes then was told by another biker with the same bike to try this. Loosen front wheel, take bike off the stand with loose front wheel. Hold front brake lever and put weight on front wheel through steering. Release brake lever. Re-tighten front wheel with the wheel still on the ground. Do NOT put it back on the stand first.
This is much easier if you have someone to help.
Hey presto - no more sticking brakes. Had the bike for another 30k and used the same procedure every time when changing front tyre. Dont ask me how ….

Ok,
Steering the loose front wheel with weight pushes the calipers piston back to their housing.
Still don't get why should they start functioning in the proper way again, but I"ll give a shot, just in case, if it worked for you, it might work for me too!

 

[motormount]

The brake lines can break down internally, especially if they are the original rubber ones. This creates a one way valve that allows fluid to push the pistons, but not to return. If the brake lines are new or stainless, this is less likely than the usual problem being that the calipers just need a thorough disassembly and service.

Paul thanks for the reply,
I changed the original rubber ones a couple of weeks ago, as they burst on my second ride, the bike was sitting idle for a long time.
Calipers were disassembled and cleaned twice, they looked good, maybe the seals are bad, but i can't "evaluate" them.
Funny thing is that the wheel became stiffer after the last cleaning.
- and when i tried an old caliper it rolled slightly better -

 

[motormount]

Yes the front ones!

Replaced all hoses from brake fluid reservoir to the calipers

 

[motormount]

Upper and lower, all the flexible hoses ?

Have you retracted the caliper pistons making sure they aren’t sticking

I retracted the calipers one by one.
Both are sticking.
The right one more than the left.
But like wrote before, dissasemping them for cleaning and aplying lubricant to the pistons,
did not notice anything "weird"
I' m waiting now for a friend to lend me a spare couple to try.
I believe it's a caliper problem, but i'd like to be sure before i order new calipers.
- or caliper seals -

 

[Paul Young]

I retracted the calipers one by one.
Both are sticking.
The right one more than the left.
But like wrote before, dissasemping them for cleaning and aplying lubricant to the pistons,
did not notice anything "weird"
I' m waiting now for a friend to lend me a spare couple to try.
I believe it's a caliper problem, but i'd like to be sure before i order new calipers.
- or caliper seals -

When you say they were dismantled, did you fully remove the pistons, polish the bores and replace the seals..? I have a friend who did mine (ex mechanic and bored retired person who wanted to do it as therapy) and he even separated the calipers to check and replace the seals between them. They came back to me like brand new calipers but had been dragging enough beforehand to warp a set of wavy discs. Seals swell and RTF or debris gets stuck in difficult to clean places.

 

[motormount]

When you say they were dismantled, did you fully remove the pistons, polish the bores and replace the seals..? I have a friend who did mine (ex mechanic and bored retired person who wanted to do it as therapy) and he even separated the calipers to check and replace the seals between them. They came back to me like brand new calipers but had been dragging enough beforehand to warp a set of wavy discs. Seals swell and RTF or debris gets stuck in difficult to clean places.

pistons were removed, polished and lubricated.

Did not change seals.


Till next Saturday, i will try a set of calipers, which i know they work properly, so i will know by then if it's a caliper issue.
- which i hope -

Where did you get the seals from by the way?

Are they original parts, or i can find similar ones from another vendor, without the BMW price tag?

 

[motormount]

Good morning all.


Tried the used friend's calipers, seen a lot of improvement, but still the wheel stacks a little.

i think it must be the disks, yet i'm tired of all the caliper removing, i'll ride it it as it is for the summer and i will see it again by winter.

 

[motormount]

update:
After a couple of days riding, the front wheel started ''stacking'' again, you could feel it when trying to turn it on the center stand, couldn't notice it while riding, or maneuvering the bike.
And a couple of days later i felt the brake lever getting softer, but i still could brake.
I thought it was my idea, and i tried to adjust the lever, but there was no change in the lever ''resistance'' either way i turned the adjustment lever disk.
Next morning i noticed the lever softening, i went to start the bike and i had no front brakes at all....
- Can't understand how i got home the night before, but it could brake even though with the lever almost touching the hand grip-
From all i could see through the brake fluid reservoir glass, there wasn't brake fluid missing.
- But the front wheel was rotating freely now at least :- P -

I took the bike to my friends garage, he called me now and said he did the brake bleeding again, and now i have front brakes and the front wheel slightly stuck....

How can this happened?
A brake gradually failing?
Without any noticeable fluid missing?

So now i will stop riding it, till my friends find some time to bypass the abs, but I'm all ears before starting, if you have any other idea.

Thanks in advance!