line to modulator/rear brake from front brake

[abush357]

I just flushed the old brake fluid from both the front and rear of my 2012, and I'm curious about the line that links the front to rear brakes. There doesn't seem to be any procedure for bleeding or flushing it, but you can find the directions in the shop manual for replacing it. Does it somehow get flushed when you do the front and rear?

 

What am I missing here?

 

 

[dirtrider]

10 hours ago, abush357 said:

I just flushed the old brake fluid from both the front and rear of my 2012, and I'm curious about the line that links the front to rear brakes. There doesn't seem to be any procedure for bleeding or flushing it, but you can find the directions in the shop manual for replacing it. Does it somehow get flushed when you do the front and rear?

 

What am I missing here?

 

 

Morning abush357

 

I'm not sure what LINE you are referring to? Your brake linking is done inside the ABS controller (pressure modulator) itself, there is no separate line for linking.  There is no "direct" hydraulic linking between the front & rear brake system, the linking is done using the rear servo pump inside the ABS controller.  

 

There is a rear servo pump inside the ABS controller (pressure modulator) for rear brake linking & also used for rear brake ABS event rear brake modulation.  

 

You can run that rear servo pump during the bleeding process by first bleeding  the rear brake system, then manually pushing the rear brake pads back away from the brake rotor, THEN turning the key on  (do not start engine) then with motorcycle on center stand spin  the rear wheel with your foot (or have someone do it for you)  then with rear wheel spinning pull the front brake lever (this should run the rear servo pump & push enough fluid through to reapply the rear brake pads & push the pads back out against the brake rotor).

 

Then just do another rear brake re-bleed. 

 

Or if you have GS-911 then just use that.  

 

 

[abush357]

Thanks for the answer Dirtrider, that is what I was looking for - so there are two lines then - one going from the front brake to the modulator/ABS controller, and one from the modulator to the rear brake. You can bleed them using a GS911, or do it manually in the way you described. That doesn't seem to be included in the BMW service manual, or in the Haynes manual, which seems odd.

 

 

[dirtrider]

12 minutes ago, abush357 said:

Thanks for the answer Dirtrider, that is what I was looking for - so there are two lines then - one going from the front brake to the modulator/ABS controller, and one from the modulator to the rear brake. You can bleed them using a GS911, or do it manually in the way you described. That doesn't seem to be included in the BMW service manual, or in the Haynes manual, which seems odd.

 

 

Morning abush357

 

There is one line INTO the ABS from the front master cylinder (hand lever) & one line INTO the ABS controller from the rear master cylinder (foot pedal). 

 

There is one line OUT OF the ABS controller to the front calipers. 

 

There is one line OUT OF the ABS controller to the rear caliper.

 

As far as the service manual goes, BMW hooks the motorcycle to their shop computer then it takes them through the bleeding procedure step by step including system test & rear servo run.  

 

On doing the initial bleed at home , once you get the first full bleed done (and you are assured it has good clean fluid in it) then all you really need to do from then on (if the bleed service is done in a timely manner) is to just bleed like normal non-servo motorcycle as the little fluid that is still in the ABS module will work it's way out then come out ion the next bleed procedure.    

 

 

[abush357]

This is making more sense - You wouldn't happen to know of a diagram of the just the brake system would you?

[dirtrider]

19 minutes ago, abush357 said:

This is making more sense - You wouldn't happen to know of a diagram of the just the brake system would you?

Afternoon abush357

 

Check your personal messages on this site as I sent you some info.

[abush357]

Hey Dirtrider, thanks again for taking the time to explain, and for sending the link.

 

For anyone else who might be interested, you can google "BMW ABS and Automatic Stability Control" and look for the webbikeworld article. Might be more than you want to know, but it does clear up why it is so easy to flush the brake system in my 2012RT.

 

cheers,

 

 

[Marvin2Shoes]

On 4/12/2023 at 11:09 AM, abush357 said:

Hey Dirtrider, thanks again for taking the time to explain, and for sending the link.

 

You can google "BMW ABS and Automatic Stability Control" and look for the webbikeworld article. Might be more than you want to know, but it does clear up why it is so easy to flush the brake system in my 2012RT.

 

 

Make sure you flush on time, every time... the previous owners of my 2011 model likely didn't. It was going to cost AU$3030 to replace the ABS unit. BTW faulty pressure sensors in these units are not replaceable... get used to the idea of big bills if the ABS quits. An ABS fault also stops your cruise control operating (if fitted) and permanently turns on your brake lamp until you power off the bike... I am still trying to figure out how BMW thought that was a clever, safe idea.