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Brakes binding - 650GS

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3 August 2017 - 10:06pm
Alistair
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Joined: 2008/07/21

Hi all

All of a sudden the rear brakes on my G650GS have started to bind. The bike is regularly serviced by BMW and on its last service about 6 months ago the brakes were checked, bled and new fluid added. The pads are good and the brake fluid level is good. The calipers/pads look clean and are not coated in mud etc.

The problem is intermittent. Occasionally after stopping (having applied rear brakes, as well as front), you can feel the brakes have not totally disengaged. The caliper and disc are also extremely hot, as a result of the friction. I assume that the pistons are not retracting enough.

Before having this checked out by BMW, does anyone know why this would suddenly occur?

Thanks

Alistair

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4 August 2017 - 6:45am
#1
Charles Oertel
Charles Oertel's picture
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Joined: 2007/04/14

Hi Alistair

First, this is an extremely dangerous situation: if the brakes start getting hot while you are riding, the fluid expands and compresses the brakes more, and you can get sudden full braking while riding at speed.

Second, there might be a number of causes:

  1. road grime and brake pad powder clogging the pistons.  Google for vids on how to clean your caliper and pistons properly.
  2. dirt in the brake fluid blocking the release port in the master cylinder.  This can be fixed by cleaning the master cylinder and cleaning the ports carefully with a pin.
  3. Most common: There isn't enough play on the brake lever, so it doesn't return to fully open.  This prevents the brake fluid from returning into the master cylinder when the brakes release, and results in pressure in the brake system.  Make sure your rear brake lever returns to fully open, and that there is at least 3mm of play.

I had this same problem and eventually replaced the rear caliper completely after trying all options and replacing various bits.

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