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Brake pressure problem

  #1  
Old 03-19-2011, 03:01 PM
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Default Brake pressure problem

Trying to put the finishing touches on my bike.i already missed out riding thursday night and friday and now I'm missing today. Got all my winter projects done and now I have a problem w the front brakes.

The front brakes are riding the rotors, and as I roll the bike they slowly lose pressure. They stop riding the rotor but I also have no pressure. I can pump the brakes up and get pressure but as soon as the wheel rotates again I lose pressure again. I tried bleeding them and there is no air in the lines. I don't know what to do and it's killing me to not be able to ride

O yea, part of my winter projects was new tires so the only time I touch the front brakes was to put the tires back on
 
  #2  
Old 03-19-2011, 03:10 PM
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I've seen this before with a set of warped rotors. The rotors push the pads back into the caliper and then you "lose" pressure for a few squeezes.
 
  #3  
Old 03-19-2011, 03:49 PM
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Bad master cylinder
 
  #4  
Old 03-19-2011, 04:55 PM
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Originally Posted by brveagle View Post
I've seen this before with a set of warped rotors. The rotors push the pads back into the caliper and then you "lose" pressure for a few squeezes.
see thats kinda what i thought may be happening, but the rotors i did have on there were warped, so i just bought some used off of somebody here, so i'm hoping these arent warped. i dont think they are, i dont notice them hitting in a certain spot then not hitting.

Originally Posted by boredandstroked View Post
Bad master cylinder
thanks ill have to check that out. what should i look for?
 

Last edited by G3NESYS; 03-19-2011 at 05:02 PM.
  #5  
Old 03-19-2011, 05:02 PM
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Originally Posted by boredandstroked View Post
Bad master cylinder
+1
 
  #6  
Old 03-19-2011, 05:31 PM
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It's never easy to give a precise answer for brake problems. You may just ahve to start by checking that the discs aren't warped first, then strip the callipers down, check the pistons are running smoothly then go for a master cylinder repair.
I've had various symptoms with my front brakes this winter, usually due to the amount of crap they've picked up of the road. A good clean has helped every time.
No easy or definitive answer though I'm afraid. Roll up sleeves, get in there and go through the possibilities.
Good luck.
 
  #7  
Old 03-19-2011, 05:44 PM
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Try this test: Bleed your brakes, get them nice a tight and then wait a day. Don't move the wheel or anything. If the brake lever goes to mush, you got a leak/bad seal, etc.

If the brake lever feels good, then i'd be looking at your rotors.
 
  #8  
Old 03-21-2011, 07:34 AM
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ok ill def try that. planned on doing it this weekend but my bike is out at my moms since i dont have a garage to work on it in... was planning on going out there sunday but then of course something else comes up. i ran over a peice of glass in my wife's envoy, ended up spending the whole afternoon at Sears getting her a new set of tires and alignment (she was due for a new set anyway we were just putting it off)

i suspect it should be a leak, etc, bc my rotors were warped last year, which is why i got these rotors, so unless these are warped worse, i dont think that would be it.

if i do the get them tight, wait a day, and they do go soft, would that mean the master cylinder needs replaced, or could it be a leak/bad seal, etc somewhere else?
 
  #9  
Old 03-21-2011, 04:39 PM
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ok i talked to my autocad teacher today, he owns like 20 bikes and is always working on them. explained the situation to him and first thing he said was rotors are warped. so i went out today and put my old rotors back on, which i know are slightly warped because they pulse when im braking. but i put them back on and the brakes are fine, dont lose pressure or anything. so i rode to work for the second half of the day just so i could get some sort of riding time in, since ive missed all the other days.

what im wondering is, does it necessarily have to be the new rotors are warped or could it be the pads that are still on there are so messed up from my first rotors that having a new set of rotors on there push the pistons away and loses pressure?
 
  #10  
Old 03-21-2011, 04:57 PM
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You answered your own question already. Get new rotors and be done with it.
 

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