sudden rear brake failure

[hotwheelzmark]

Hello, I am a new rider and new to this forum.

I recently purchased a 2007 fz6 with 5000k miles 2 weeks ago and today while riding it I suddenly had no rear brakes (pedal went to the floor with no effect) thankfully was able to stop with fronts without wrecking.

I stopped and investigated, first pads were tight on rotor, whole assembly was scalding hot. brake fluid was full, linkage fine. After it cooled down the brake pedal had pressure again . I got a wrench and pryed the pads off the rotor and drove home slow, downshifting, front brakes.

what would cause this and how expensive to fix?

 

[hotwheelzmark]

Pads also have plenty of life, rotor is clear (no oil on it) also the caliper cyclinder moves back and forth by hand now. Like I said this is only my second summer of riding , traded in a 250 rebel for the fz6 so this is a drastic change lol. Is it possible I accidentally had my foot on the brake whike riding (not used to the peg location quite yet) or is the master cylinder blown?

 

[TownsendsFJR1300]

As the bike is new to you, I would flush and bleed out the rear brake system. If you have some air/moisture in there, it could cause some dragging. To that extent, probably not..

If your halfways mechanically inclined, I'd pull the caliper off, clean whatever goo/dust is built up on the piston. The rear caliper on the bike floats on two pins/bolts and centers itself. Those pins need to be lubed with brake specific grease so the pins move in the caliper with no resistance.

Even if you not mechainically inclined, get some brake cleaner and spray any build up out from the pads, etc..

The front brakes on the 07 tend to drag, pretty much not an issue on the rears.

That piston should move in and out fairly easily. Its rare the master cylinder is the issue.

And yes, if your foots resting hard on the rear brake lever, it'll activate the brakes and the disc will heat up.. You can adjust the lever height, kits in the owners manual...

Please post what you find.

 

[hotwheelzmark]

What could cause this amount of dragging? And the sudden complete failure? I was riding into the wind so I probably didn't notice the dragging and I was going about 65 for 10 miles or so before I tried to stop. I'm guessing it musta been dragging that whole time to generate the amount of heat.The rotor, caliper and even wheel was immensely hot.

 

[TownsendsFJR1300]

What could cause this amount of dragging? And the sudden complete failure? I was riding into the wind so I probably didn't notice the dragging and I was going about 65 for 10 miles or so before I tried to stop. I'm guessing it musta been dragging that whole time to generate the amount of heat.The rotor, caliper and even wheel was immensely hot.

As posted above, if there's crap in the caliper/assembly, keeping the piston from returning, the brakes are applied 100% of the time.. Yes, it will get extremly hot.

It needs servicing/cleaning at the very least.

 

[hotwheelzmark]

As posted above, if there's crap in the caliper/assembly, keeping the piston from returning, the brakes are applied 100% of the time.. Yes, it will get extremly hot.

It needs servicing/cleaning at the very least.

Thanks for advice! I will take it to the local shop to be cleaned and I will post what the problem was when they find it. I hope it's something that simply and not a blown master or caliper piston

 

[TownsendsFJR1300]

Its possible a wheel bearing is bad, but the above is most likely the issue.

I would look in the shop manual and peek at the brake assembly. Its not terribly complex, especially just to clean.

If you don't have brake bleeding / flushing experiance, do a search on the forum, its not terribly difficult to do..

 

[FZ09Bandit]

I just want to ask why you seem to not like using the front brakes?

2 big ass rotors on the front, one smallish on the rear.

Had air in te lines when I had my gsxr you had to pump the rear brakes, but was never an issue because I don't use a lot of the rear brakes.

 

[Carlos840]

I just want to ask why you seem to not like using the front brakes?

2 big ass rotors on the front, one smallish on the rear.

Had air in te lines when I had my gsxr you had to pump the rear brakes, but was never an issue because I don't use a lot of the rear brakes.

+1

This comment "thankfully was able to stop with fronts without wrecking" had me very confused!
Your front brakes are a lot safer than your rear, and provide 80% of you braking power.

 

[tyler2011]

I stopped and investigated, first pads were tight on rotor, whole assembly was scalding hot. brake fluid was full, linkage fine. After it cooled down the brake pedal had pressure again .

Since you mention there was heat radiating from the disk and caliper, and once cool the petal had pressure again, I suspect it got hot enough to essentially boil the fluid in the caliper. This will cause a very soft petal and very limited braking. With the mall caliper in the rear it may have equated to virtually no rear brake. Brake fluid absorbs water over time, reducing its boiling point. This is one of the reasons it is recommended to flush it regularly, I belive about every 2 yrs. It often does not get done.

I personally only use very little rear brake in regular riding and more for low speed maneuver (<10 mph) speed adjustments.

Either way, the cause of the brake dragging needs to be adressed. You should be able to rake a short ride, stop with only the front brakes. Be careful but at this point since you have not used the rear brake, it should be cool or maybe sligtly warm.

As previously mentioned, I would be cleaning the rear caliper and slide pins. Then do a fluid flush of the rear brakes.

Sent from my DROID3 using Tapatalk 2

 

[Red Wazp]

Be very sure you foot was not on the brake lever. With just slight pressure from you foot is enough to engage the rear pads to the disk but not enough to notice while riding. Once you heat up the fluid the brake stops working,
As you found out once it cools down the brake works fine.

 

[DeepBlueRider]

What could cause this amount of dragging? And the sudden complete failure?

When you have a drag, whole brake system (caliper, pistons and at least fluid) gets hot. So hot brake fluid boils ! Especially when you have older fluid it accumulated lot of moisture. When your brake fluid boiled, it vaporized to gas. Gas in opposition to fluid can be compressed (think about it as squeezing). So if that was a case for you, air gap happen, and when you pressed pedal it went all way down compressing air gap without transferring pressure to brake pistons.