Rear Brake failure
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Stage II
Joined: Aug 2013
Posts: 2
Likes: 0
From: Canada
Rear Brake failure
Hi, I have a 2001 Road King (Concorde Purple <3 )
I admit, I am a FRONT brake addict and rarely, ok NEVER, use my rear brake. Recently I decided I really need to change this HORRIBLE habit but every time I use my rear brake (this has happened before) my rear brake goes all the way to the bottom with no braking result. Master Cylinder is full, no leaks. Any thoughts?
I admit, I am a FRONT brake addict and rarely, ok NEVER, use my rear brake. Recently I decided I really need to change this HORRIBLE habit but every time I use my rear brake (this has happened before) my rear brake goes all the way to the bottom with no braking result. Master Cylinder is full, no leaks. Any thoughts?
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
well, you need the rear brake on wet or loose surfaces.
maybe bad seal(s) in master cylinder, maybe seal(s) in piston.
you'll just have to go through the system
mike
maybe bad seal(s) in master cylinder, maybe seal(s) in piston.
you'll just have to go through the system
mike
Grand HDF Member
Joined: May 2008
Posts: 4,585
Likes: 673
From: Rolla
Hi, I have a 2001 Road King (Concorde Purple <3 )
I admit, I am a FRONT brake addict and rarely, ok NEVER, use my rear brake. Recently I decided I really need to change this HORRIBLE habit but every time I use my rear brake (this has happened before) my rear brake goes all the way to the bottom with no braking result. Master Cylinder is full, no leaks. Any thoughts?
I admit, I am a FRONT brake addict and rarely, ok NEVER, use my rear brake. Recently I decided I really need to change this HORRIBLE habit but every time I use my rear brake (this has happened before) my rear brake goes all the way to the bottom with no braking result. Master Cylinder is full, no leaks. Any thoughts?
You really need that rear brake, or your gonna dump your bike one of these days.
With that out of the way, you either have a leak (may not be external) or you have air in the line.
Fluid will not compress, so the only way your brake pedal is going all the way down, is if you have an external leak (you ruled that out), air in the line, or the fluid is bypassing the piston in your master cylinder bore.
Thread Starter
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Stage II
Joined: Aug 2013
Posts: 2
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From: Canada
Wow, you are an accident just waiting for a place to happen.
You really need that rear brake, or your gonna dump your bike one of these days.
With that out of the way, you either have a leak (may not be external) or you have air in the line.
Fluid will not compress, so the only way your brake pedal is going all the way down, is if you have an external leak (you ruled that out), air in the line, or the fluid is bypassing the piston in your master cylinder bore.
You really need that rear brake, or your gonna dump your bike one of these days.
With that out of the way, you either have a leak (may not be external) or you have air in the line.
Fluid will not compress, so the only way your brake pedal is going all the way down, is if you have an external leak (you ruled that out), air in the line, or the fluid is bypassing the piston in your master cylinder bore.
I will look into these and keep you posted on the solution. Since this ISN'T the first time this has happened, WHY does it keep happening? If it's air in the line should just pumping it help? Even if it's abandoned it shouldn't do that...should it? Therefore a seal issue as mentioned etc?
Seasoned HDF Member
Joined: Feb 2007
Posts: 6,086
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From:
You state : Master Cylinder is full, no leaks & no braking.
Is the rear rotor warped? did you change the tire and someone banged the rotor?
Consider placing bike on a lift or figure something out so rear tire is in the air.
Rear tire just off the ground is enough.
Spin rear tire with your HAND slowly and look at rotor as it passes through caliper.
Does rotor wave from side to side as it passes caliper area?
Is the rear rotor warped? did you change the tire and someone banged the rotor?
Consider placing bike on a lift or figure something out so rear tire is in the air.
Rear tire just off the ground is enough.
Spin rear tire with your HAND slowly and look at rotor as it passes through caliper.
Does rotor wave from side to side as it passes caliper area?
Outstanding HDF Member
Joined: Dec 2009
Posts: 2,502
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From: Lapeer , Mich
could be air in the system from not being used that would burp back into the master cyl if it is just a little , other than that I would have to say master cyl bad or needs to be pumped back up
Grand HDF Member
Joined: Dec 2007
Posts: 4,999
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From: Bay Area
How old is the fluid in the rear? It may be broken down to the point of it being the equivelant of a 1 weight oil and by passing. I believe that year may be a dot 5 fluid (Im doing a system rebuild on an 02) if not it still may be a dot 3 which is very susecptable to moisture breakdown. If youre not sure D5 is purple and real dark if dirty, and D3 is a yellowish and dark when dirty.
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It's either the caliper or a master cylinder problem. You could have 2 problems is your pedal hard or spongy I would take screwdriver & gently try to pry the piston back in the caliper then pump the pedal the pads should push back out to the rotor if not replace the master cylinder 1st. Then checkout the caliper for movement if not rebuild it. That should solve your problem.
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Ultimate HDF Member
Joined: Jul 2012
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From: Northwestern Nevada
My guess for the repeated issue is poor maintenance. You might have debris in the fluid causing the seals to fail, allowing the piston to pass without building pressure. Old break fluid is an accident waiting to happen. My advice is to rebuild the master cylinder, and caliper(s) and replace the fluid. Don't forget to bleed the system before you finish. No matter what the problem is/ was, that is probably going to fix it...baring the possibility of a new issue being introduced, a leak you had not seen, or missing components. Just a thought, if the break pads are missing the peddle might go to the "floor" even is there is pressure without causing the caliper to contact the disk.
