Rear break soft on RR

[antonio_beqa]

Hello i have such problem on Rear break , while i push pedal first time it goes fully down and on secund push it looks cool , i try it on all modes and also abs off and on , its same , also while bike is stopped in place i check it and same ,so it would not he break pads or rotors , i have new oem brake pads and also new brake fluid , it was doing same in old pads and brake fluid

I have done a lot of break bleeding mabe 1 litre brake fluid i used to bleed my rear brake but its doing same , i also used GS911 to bleeding but same what would be the reason that in first push pedal is softer and goes fully down and in secund push everything is ok ? If i will not push pedal 15-25 sec then again its soft at first push

 

[bananaman]

Has to be air I'm thinking..... Have you tried taking the calliper off and holding it as high as you can then bleeding?

 

[mike g]

have a look at the caliper sliding pins, mine felt ok in that you could move the caliper / piston by hand, but a good clean and regrease sorted it out after all that pads, bleeding and disc run out malarky (only took me 6 years to do!)

 

[antonio_beqa]

I have done a lot of bleeding with manual and with gs911 also i dont know how there would be air in sistem , is it possible that master cylinder has damaged ?

 

[stuartb]

Is it a stock rear caliper ?... last one of these I had on the ZX forum and figured it out..... turns out guy had an aftermarket caliper, slung upside down and nipple was on the bottom most part of the caliper !..

Throw some images on mate, helps us figure out what's what..

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[stuartb]

Also, did you follow the correct procedure with 911 purge.. I done mine last week so it's fresh in my head .

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[stuartb]

Spot the nipple !

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[antonio_beqa]

Everyrhing is oem caliper reservior , pedal , pads ,

In GS911 there is break bleed test but there is not written font or rear when i start testing it wrotes me to push pedal 3 time in 10 secund testing so while it starts bzzzzz sound of abs i am pushing rear pedal for 2 sec each time and doing it 3 time after thet it wrotes test 2 amd doing same thats it

Do i need to do somthing more with gs911 ?

 

[stuartb]

Beyond that.. the instruction is "Then bleed manually if required"...so run the test and bleed manually.... presumably you don't let the res run dry ? and do you use a bleed bottle with a non return valve ?.. if not Halfords do one for 6 quid, cheap and works fine..

The front and rear are done separately.. look again, if the M/C seals were fucked you wouldn't get a pedal under any circumstance..


Post some images of your set up

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[alex]

1st press they are always soft IMO. Just a lot of fluid/piston pullback.

 

[antonio_beqa]

I changed mc from friends bike and problem solved , so its Master cylinders fault , is it possible to repair and how ? Mabe clean it needs ?or if i buy used one is there differens betwin model of rr with year ?

 

[stuartb]

WIthout checking I'm sure you can buy a kit for it.. usually consists of spring, piston, seal, dust cover, circlip.. either that or buy a complete new unit, their not hugely expensive..I'd open up the old one for investigation purposes..

It's quite rare a m/c fails, particularly a rear.

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[mike g]

believe they are all the same and rebuild kit is not available

 

[JamieMac]

Brembo do a 13mm repair kit. Take yours apart and you can match it. To be honest it?s only ?50 odd for a new master cylinder from Brembo. Not via BMW.

 

[scooby]

are you UK based? pretty sure i have a new rear m/c in my spares.

 

[JamieMac]

I?ve just checked my spares and I have four spare. Happy to post. Silver or black finish.

 

[antonio_beqa]

Thanks guys i have already bought MC just waiting to recive it and i will post what will heppens but sure it will fix my problem becouse i tested my friends MC on my bike same RR and it was working cool , cleaned mine re installd and again same shit so it is MC for sure

 

[scooby]

I?ve just checked my spares and I have four spare. Happy to post. Silver or black finish.

i've got 4 aswell haha no idea why!!