R1200RT rear brake pistons stuck

[RTRay]

I changed the rear brake pads on my 2013 RT, as I’ve done before, and after doing so the pistons won’t come back out of the cylinders when I compress the brake pedal or the front brake or both, either with the bike running or off. The pistons were compressed slowly back into the cylinders as I’ve always done with no problems. Now I have no back brakes and no way to get the pistons to extend normally.

Is there any way to force the pistons back out? The brake fluid level is correct.

Any ideas how to correct this?

 

[etiennelau]

I had similar issues with my 2010. In my case the slide pins were corroded. I bought a used rear caliper from eBay and swapped parts and cleaned everything. Basically combined good parts from the 2 rear calipers to make a working unit.

 

[05biggray]

Did you bleed brakes ? If so and have fluid coming thru back brakes problem is in brake caliber if not then abs system is not allowing fluid thru.

 

[AntonLargiader]

@RTRay did you figure it out?

 

[RTRay]

@RTRay did you figure it out?

No. It’s at my mechanics shop now getting fixed.

 

[AntonLargiader]

I'm interested in reading about the outcome. As you surely know, you should be able to pump the brakes and get the pads back out, although with new pads there generally isn't much pumping needed. Seems to me that either the MC is moving fluid or it's not... if it is, it's going somewhere. And if it's not, the reason should be discoverable.

 

[RTRay]

My mechanic says there’s no pressure coming from the abs unit to the back brake.

How do you get the abs unit to reset itself?

 

[AntonLargiader]

It's normally a pass-through system. Pushing fluid in from the master should simply result in it going out to the caliper. Is there pressure at the pedal? If there's pressure at the pedal and it's not making it to the caliper that is a new one for me. I'd be reading the codes for the ABS unit. Then I would be disassembling the system to look for a blockage.

 

[RTRay]

It's normally a pass-through system. Pushing fluid in from the master should simply result in it going out to the caliper. Is there pressure at the pedal? If there's pressure at the pedal and it's not making it to the caliper that is a new one for me. I'd be reading the codes for the ABS unit. Then I would be disassembling the system to look for a blockage.

There’s no pressure at the pedal. It is soft.

 

[RTRay]

My mechanic said there’s no pressure at all coming from the ABS unit so he bypassed the unit and I now have a functioning rear brake that doesn’t go to the ABS. The front brake operates normally but with no ABS. The weird thing is that the ABS light isn’t on at all. Not solid red not flashing nothing. I don’t have a GS911 but will buy one to see if I can get any info on the problem. I may need to have the ABS rebuilt this winter.

 

[AntonLargiader]

If there's no pressure going in I sure wouldn't expect to find pressure going out. Seems to me, either fluid is going into the ABS unit or it isn't. Each has its own set of things to follow up on. It's extremely unlikely that it's just going into the ABS unit and not coming out anywhere. But the bike isn't in front of me.

 

[bhodges]

When the front brake lever is applied the rear brake is activated by the pump in the ABS. When you use the brake pedal it operates a master cylinder that passes thru the ABS without the use of the pump. It sounds like something is plugged in that circuit. Was your ABS working before you replaced the rear brake pads?

 

[RTRay]

When the front brake lever is applied the rear brake is activated by the pump in the ABS. When you use the brake pedal it operates a master cylinder that passes thru the ABS without the use of the pump. It sounds like something is plugged in that circuit. Was your ABS working before you replaced the rear brake pads?

Yes, the brakes were working fine before the pad replacement. I'm going to take the bike to an actual BMW dealer and have them go through it. My local mechanic is a Honda mechanic who rides older BMW's and works on them, but doesn't have the tech for the more modern bikes. It might be something simple, or maybe not.