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1200RT rear brake drag culprit found


gdouglas

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Well, I finally found out what was causing my rear brake to drag slightly for the past few thousand miles. One of the guide pins that permit the caliper to be free floating was seized up in the caliper bracket. This was causing the left pad to drag with some residual pressure since the caliper couldn't float back to a properly released posistion. I caught holy hell getting it unstuck, but everything is still serviceable after some cleanup. All I have to do is to replace the rubber boot seal ($28 BMW kit)to make things weather-tight again.

 

What puzzles me is that the rubber boot that is supposed to seal this floating joint assembly was intact as designed, but absolutely no lubricant was found inside this sliding joint. The other guide pin and boot seal was fine, with proper signs of lubricant. I can only assume that with the boot seals intact, my problem guide pin was without any lubricant from day one.

 

I was fortunate to get it apart with out having to destroy the caliper bracket and the caliper ($123 and $522 respectively). Whew!

 

Next time any of you are doing maintenance work around the rear wheel of your bike, it would be adviseable to check the free floating function of your rear brake caliper. Hopefully, my bike was just a random one-off from the factory that didn't happen to get any lube on that guide pin.

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Funny you should mention that, but I had the same problem and the dealer gave the bike a clean bill of health (??????). However, after servicing my final drive, which required removing the rear brake caliper, I found that the drag was much less after re-installation. I think I'm going to double check that myself.

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I hope BMWNA is lurking so that a service bulletin can be issued. This observation could solve more than a couple of unusually fast brake pad wear problems. Good find!!

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how did you detect the drag? Just by rotating the wheel when on the centerstand?

Mine does rotate easily but drags a little, I can hear the pad rubbing a little.

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I found out by noticing that the noise of a pad rubbing the rotor was a little more pronounced than usual when pushing the bike into the garage. This along with only 10k miles to a rear set of pads.

 

After a long local ride, I could put my hand on the rear caliper and it had a little warmth to it, as compared to the front calipers which were pretty much ambient temperature. I started getting curious from there.

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Next time any of you are doing maintenance work around the rear wheel of your bike, it would be adviseable to check the free floating function of your rear brake caliper. Hopefully, my bike was just a random one-off from the factory that didn't happen to get any lube on that guide pin.

 

Excellent information - just added to the winter pm list!

 

Thanks

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