Rear Brake Issue help

[CutterBill]

Let me tell you a story....

Back in the days of the Red Dog Saloon, I owned an auto repair shop.  One day a truly ancient Mercedes-Benz rolled into the shop with a weird problem.  Seems if you applied the brakes (while driving) the car would dart hard to the right.  If I muscled the car straight with the steering wheel and kept pushing on the brake pedal (as in coming to a stop) the car would eventually stop pulling to one side.  But then when I released the brake pedal (car still moving) the car would now dart to the left.  Much head-scratching ensued...

Eventually we discovered that the left brake hose looked perfectly fine on the outside, but had swelled almost completely shut on the inside.  The right brake would get pressure just fine and the left brake would not, causing the hard swerve.  But eventually, with continued pushing on the brake pedal,  the master cylinder would develop enough pressure to slowly bleed past the restriction in the hose, and now the left brake would work.  But when I let off the brake pedal... here's the important part... the swollen hose would keep pressure in the left brake, causing the car to swerve the other direction.  In other words, the hose was acting as a one-way check valve.

We replaced all of the brake hoses, bled the brakes, and the customer drove away happy.

It is entirely possible that you have a bad hose, and it is not allowing the pressure to bleed off.
Bill

[movenon]

Let me tell you a story....

Back in the days of the Red Dog Saloon, I owned an auto repair shop.  One day a truly ancient Mercedes-Benz rolled into the shop with a weird problem.  Seems if you applied the brakes (while driving) the car would dart hard to the right.  If I muscled the car straight with the steering wheel and kept pushing on the brake pedal (as in coming to a stop) the car would eventually stop pulling to one side.  But then when I released the brake pedal (car still moving) the car would now dart to the left.  Much head-scratching ensued...

Eventually we discovered that the left brake hose looked perfectly fine on the outside, but had swelled almost completely shut on the inside.  The right brake would get pressure just fine and the left brake would not, causing the hard swerve.  But eventually, with continued pushing on the brake pedal,  the master cylinder would develop enough pressure to slowly bleed past the restriction in the hose, and now the left brake would work.  But when I let off the brake pedal... here's the important part... the swollen hose would keep pressure in the left brake, causing the car to swerve the other direction.  In other words, the hose was acting as a one-way check valve.

We replaced all of the brake hoses, bled the brakes, and the customer drove away happy.

It is entirely possible that you have a bad hose, and it is not allowing the pressure to bleed off.
Bill

Had the same problem in a 56 Nomad that was "restored".  I replaced all the lines and no problem after that. What was an eye opener is the large diameter looking brake hose when cut open the feed hole was around only 1/16 inch in diameter or less.  Recently I observed a neighbor doing his own brakes and had a heavy caliper off the rotor and dangling down by the hose. I cringed. 
George

[MOTOMYSZOR]

I cleaned up today whole system: and again was hard to press back pads - compare to force needed without calliper connected to the system and compare to force needed on front callipers

Then I realised that since beginning I have doubts about rear disc temperature..... Even after change to Fazer 1000 brake system and later braided line.

So I took out master cylinder and I tried clean relief port with thinnest wire at home: I tried split cable, fishing line...... Actually I did not try human hair.....  I could not press inside anything....

So I decided: drilling. I used 1 mm drill. After I assembled all together finally I can push back pads without any problem. Braking is extremely good and rear disc is finally cold when not in use.....

I will give it few more miles tomorrow. And probably I will buy spare MC from non ABS FJ....

[MOTOMYSZOR]

Few observations after today's ride:

- much easier to push bike back or forward while sitting on it
- different feeling when I use rear brake. Now I can much more precise dosage braking power.
- Brake disc is cold when not in use. It is getting very hot even after short braking, I checked on internet and it seems that it is normal in Fazer.

Minus: Voice in my head whispering: You idiot - You tampered with brakes.....

[ribbert]

..........  Recently I observed a neighbor doing his own brakes and had a heavy caliper off the rotor and dangling down by the hose. I cringed. 
George

George, this is one of our very own members bikes recently with calipers hanging by the hoses.



While probably not a good habit, those lines have to withstand approx 350 lbs minimum tensile strength to pass the required standards and most manufacturers are going to exceed that by a considerable margin. Brake hoses are a lot tougher than most folks think.

As I said, I wouldn't recommend it but it's probably not doing any harm either.

Noel

[krusty]

I cleaned up today whole system: and again was hard to press back pads - compare to force needed without calliper connected to the system and compare to force needed on front callipers

Then I realised that since beginning I have doubts about rear disc temperature..... Even after change to Fazer 1000 brake system and later braided line.

So I took out master cylinder and I tried clean relief port with thinnest wire at home: I tried split cable, fishing line...... Actually I did not try human hair.....  I could not press inside anything....

So I decided: drilling. I used 1 mm drill. After I assembled all together finally I can push back pads without any problem. Braking is extremely good and rear disc is finally cold when not in use.....

I will give it few more miles tomorrow. And probably I will buy spare MC from non ABS FJ....

To clear that little hole all you need is a piece of #1 E guitar string. Small enough diameter to get in the hole and stiff enough to shift the crud.