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Discussion Starter #1
Hi everyone... I need some help again.

I was riding along a lovely country road and noticed drag increasing steadily. I down shifted and the bikes front brake increased rapidly until I came to a standstill and it was on hard! I couldn't move the bike at all. This all happened within the space of about 500m.

Off/On with the ignition and a little rest and it freed up. I rode it again to test it and it seamed fine, but the same problem happened within another 5k and now there's permanently about 30% of the front brake on. (Rear brakes are fine at this point.)

Upon further inspection, nothing seams up with the callipers, and no obstructions to the lever. Nor are there kinks in the hoses or loss of oil (neither in the reservoir or signs of leaks). The fluid is clear. There are no warnings or lights on the dash.

My fingers are pointing at the ABS having thrown in the towel, but are my assumptions correct? Is it repairable or just replace? any ideas on prices and/or whether the work has to be done by BMW?

Has this happened to anyone else? Any help would be gratefully appreciated!

(the bike is a 2007 BMW R1200GS with Brembo brakes but with BMW branding, from the times when I guess they collaborated)
 

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I have had brakes drag due to old neglected brake fluid. Also with old calipers. Some brake hoses can deteriorate on the inside and not let the fluid release pressure. I would start by draining the brake fluid and bleeding the new stuff.
Next take the calipers apart and inspect.
UK
 

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What Krusty said!!!!
What you describe is fairly common because most people will NEVER replace their brake fluid as long as their brakes still work. Linked and ABS brakes require much more frequent draining and flushing. The Pistons within the Calipers tend to seize up if things are worn out or dirty.
Sam:)
 

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I haven't had the issue with a bike yet, but definitely had it on my car recently. The car doesn't get driven when I can ride, so it sat for a few weeks, then one rainy day I drove it. The brake started dragging so bad that by the time I got to work the wheel was smoking. Changing a $12 flex hose at the driver's side front wheel fixed it. The rubber breaks down and collects inside the line where it acts like a one way valve. Fluid goes in under high pressure from your master cylinder, but doesn't go out so good because there's not much pressure differential when you release. Bleeding a few drops from the caliper bleeder can keep you motoring, smoke free, in a pinch.
 

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I should have mentioned that the "brake drag increasing steadily" phenomenon the O.P. mentioned is accounted for by a little air (or water) in the caliper. As the brake drags and heats up, it vaporizes the water and/or heats the air. Since any gas pressure increases proportional to it's temperature, the increasing pressure, increases the drag, which increases the heat, which increases the pressure, and so it goes.

If the hoses aren't acting as one way valves, the excess pressure gets pushed back into the master cylinder, but the water vapor, (brake fluid is hygroscopic, it loves water) will still do a number on the system components, corroding them from the inside. It's smart to flush the fluid out occasionally, like the book says, and the damper the environment, the smarter it is.
 

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If your bike still has the original rubber brake hoses you should replace them as soon as possible with braided stainless steel. This is a common problem with BMW motorcycles of the era. Actually, any rubber brake hose will deteriorate, but this was especially common on the BMWs. And the ABS controllers and calipers pay the price for the little bits of rubber and crud that gets into the brake fluid.
 

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Discussion Starter #7
Wow thank you for all your fantastic help! I've really taken for granted working brakes and I'm going to get the fluid changed and change hoses asap

I've actually found the problem that I thought I'd share out of interest sake. It is stupid - I feel like a bit of an idiot.
61180


Whilst riding a bit harder and with weight more on my wrists, I must have moved the throttle/switch housing (which must have been slightly, microscopically loose) around until its conflicted with the brake cylinder and kept it depressed.

there was nothing obvious at all in the look of things

Turns out to be a really simple fix, but I'm going straight to the garage when quarantine is over to get it overhauled, fluid changed and hoses looked at!

Thanks for all your help!!
 

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Glad it was something simple. Thanks for closing the loop and sharing your find. This will likely help somebody else in the future.
 

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Thank you for letting us know the solution. So often someone comes here with a problem and then we never hear from then again. This may help someone else in the future.
 

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First off, I was going to suggest that something may be pressing on a valve or wire. I say that as it happened to me when my foot brake reservoir arm (?) was not releasing all the way as it was binding up just enough that the brake fluid would compress like normal, but since the valve was not returning all the way, the pressure kept building up until the calipers locked up. So if a brake situation arises, one must check the entire route of brake line--every inch along the way.

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