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Sticking Front Brakes????


edlam

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Hi All. New here and my first Post is a question. I have a '97 R1100RT and I think my front brakes are 'sticking.' Just noticed this today. Stop at a stop light and the bike doesn't 'roll' around like it used to. Kind of have to force it. So. I get home and check it out. Bike on center stand. Apply front brake and release. Try to turn front wheel and lots of drag. Wheel frees up after a few rotations. Is this a bad caliper? I see the brake pads 'float' on pins. Do you guys think the pads are not 'letting go' and still grabbing the disks? Or is this a sign of bigger problems? I hope not!! Been reading lots about these bikes. Is this maybe those rotor bobbin things gone bad? Do I need to change the brake fluid? Any help is welcomed. Thanks and, I love this place! thumbsup.gif

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Not the bobbins. What you have is either rusting pistons or old rubber lines.

The lines can swell causing flow restriction especially on return pressure causing sticking pads.

or

The pistons are developing rust also resulting in poor return.

 

Since you live in Oregon most likely rust and since the lines are almost 10 years old change them too..

Time to do some wrenching.

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One thought,take the filler cap off and try again,if the brakes no longer stick than you have a blocked breather in the cap grin.gif Thats the easy solution,if not start with the pistons and spend your way back from there frown.gif

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What Tony mentions are possibilities, also a plugged front master cylinder that is not allowing the fluid to back flow and release the pistons is possible.

 

When was the last time the bike had a brake system flush and bleed?

 

How much drag are we talking about? Enough that it is work to rotate the front wheel, or just a bit of drag that can be heard? If you take the cold bike for a ride and never use the front brake during it, does the rotor heat up too hot to touch, or just gets a bit warm?

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Thanks for all of the information. The records indicate that the last brake fluid change was done two years ago (in September). I wonder if I should do that.

 

The drag only happens after riding on the interstate for a few miles and then a mile or so of surface street, stop and go. I notice that after a few blocks that I sense the front wheel sticking. I don't have to force it. Just nudge it.

 

I know on cars, if the brakes drag the fluid gets hot in the calipers and can cause sticking. I also read on another site about the guide pins that hold the pads. The pins can rust and not let the pads retract. Is that worth lookin at? Like lightly polishing these pins?

 

Ken - it is just a bit of drag if I move wheel by hand. I do not have to force it.

 

How do I clean the master cylinder vent? Flush the fluid?

 

Thanks clap.gif

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The first post I read in to it what I'm used too.

It's funny I forget that BMW bikes actually get maintained!

 

I've spent so much time fixing screwed up bikes that have the worst of neglect that when a BMW guy says my brakes are sticking it's probably not what I see all the time.

 

I have a pile of frozen calipers and pitted pistons and rotten lines in my garage so to me it's the norm!

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Another thing to note - lately I have noticed that my brakes have felt more firm to apply - not as mushy (not that they were really mushy before). Does this add any more information to the collective wisdom here? Tanks!

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lately I have noticed that my brakes have felt more firm to apply

 

Replace the hoses. They are restricting the fluid return to the master cylinder reservoir and this leaves your brakes parially applied. At some point they will get worse and totally prevent the fluid from returning and your front wheel will lock up dumping you on your a$$.

 

Stan

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it is just a bit of drag if I move wheel by hand. I do not have to force it.

 

How do I clean the master cylinder vent? Flush the fluid?

 

Well it's of course hard to tell 'from here' so to speak, but I'm not sure you actually have a problem. All disk brakes drag some. Only by comparing it with another bike can you maybe conclude if yours is dragging worse than others.

 

ISFA cleaning the master cylinder, the first thing I would do is pull off the cover and have a looky-see in the bottom. Is the fluid clear to the bottom or milky / cloudy? If the latter probably the only right way to clean it is to disassemble it and install the rebuild kit.

 

If the former, does the return hole look clear (the one closed to the hose exit point)? When you squeeze and release the brake can you detect fluid back flowing into the reservoir though the hole? Sometimes they can be cleaned out carefully with a tooth pick.

 

Certainly the other things mentioned in this thread are possibilities too. Sticking pistons, sticking pads on the guide pins (removing and polishing them is a good approach), bad hoses, old fluid expanding.

 

It's just going to take some explorin'

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i know that feeling because last year when i had a leaky front master cylinder and proceeded to replace it by ordering the rebuilt kit. i also took the opportunity to change the front pads. in my not taking notes mentality, i over tighten the shaft with swivel that hand lever connects to and ultimately pushes the plunger into the master cylinder.

the problem was so bad in the cold october morning that the bike would stall in 3 gear . the problem would go away in the afternoon when the o rings warmed up on the plunger or allowed the spring to push the plunger back out to release the loc\binding on the rotor. i backed the screw out 3 turns and the problem went away. scarey as i did not need the brakes until i got on the highway and then it would stick after a hard brake exercise. 2nd or 3rd gear and high rpms plus the smell burning will unnerve you. the rotors got hot too.

check the plunger to make sure it isn't binding.

good luck

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Yes, defintely check the grub screw (the adjuster screw in the brake lever that actuates the master cylinder plunger, can be easily seen after removing the plastic cover in the front of the front brake assembly.) If this is too tight it can cause your symptoms. Of course so can any of the other items mentioned but this is an easy first thing to check. To adjust, the grub screw should be backed out, then tightened just until there is no excess play in the brake lever, then one-half additional turn in (and no more!) Try this and see if your front wheel turns freely (although as Ken noted a little drag is normal.)

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One thing I neclected to mention because I forgot all about it - a few days ago a pedestrian jumped out in front of me while i was riding through the grocery store parking lot. I hit the brakes harder than I ever had on this bike. Seems to me this problem started right after that I just didn't put the two together. Does that rule out hoses? I looked for hoses on MAX BMW and can't find the two that go to each caliper...

 

So this weekend I am going to look at the grub screw, flush the fluid and clean up the guide pins. Sound like a good start? How much are hoses?

 

TIA

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Does that rule out hoses?

 

No. Your hoses are old. Old hoses degenerate internally and sometimes restrict the flow of brake fluid. This affects the return of fluid most because it's there isn't a lot of pressure then. This doesn't affect applying the brakes because that's a high pressure operation.

 

If you try everything else and it doesn't fix your problem, replace the hoses.

 

If flushing the brakes gets you any small particles of rubber, replace the hoses.

 

If you plan on keeping the bike forever plan on replacing the hoses about every 10 years or so. Sooner if they develop problems. I'll probably do those on my '96 RT this winter.

 

Stan

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A good friend of mine just bled his 1100 system. It has the grub screw in the right caliper and his brakes were dragging as well. When he removed the grub screw /heat was required/ the fluid was dark. New speed bleeders were installed and he flushed the fluid from the left and right side...the right side eventually cleared up...and now his brakes work very well. It even improved the lever feel. BTW, according to service records, the brake fluid had been changed in the not too distant past. IMHO, the grub screw should come out and replace with a standard, or speed, bleeder.

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Well Stan was right. I checked out the brake pad pins today. They were all rough so I thought that was the problem. I cleaned them up with some 0000 steel wool and viola! Things seemed all better. I decided to flush the fluid then. Bled the right side - no problem. Nice clean fluid. Go to do the left side and no fluid at the bleeder. Pump some more. Nada! My wife came out to see what was going on. I ask her to help me bleed and when she was squeezing the brake lever, I see the left brake hose SWELLING up like a puffed up sea frog! A big old bulge when the brakes were applied. I feel better now, but I am not riding the bike until I get a new hose (I hope this week). Thanks everyone!

 

Ed

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