Poor breaks after new birfs?

Discussion in '80-Series Tech' started by Curran, Jun 22, 2005.

  1. Curran

    Curran

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    I just threw in some new Longfields in the front for the upcomming weekend at CMCC ( :) ) and now my brakes feel rather week. I can stand on the break pedal with both feet and can't get 'em to lock up.
    Any suggestions on what to look for or check? :confused:

    Curran
     
  2. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    Did you open up the hydraulic system?

    What happens if you pump the pedal?
     
  3. Curran

    Curran

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    I really didn't mess with the brakes aside from moving them out of the way to get inside the knuckle.
    I'm dumbfounded. I've removed the breaks twice previously in the same way with out issue.
     
  4. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    OK,

    Are the wheel bearings adjusted properly?

    And, what happens if you pump the pedal?
     
  5. Curran

    Curran

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    If I pump the pedal, there is not much of a difference. You can feel a bit of pressure build up, but it gradualy fades away and doesn't seem to decrease stopping distance. I wonder if I could have jamed a brake piston some how.
     
  6. Curran

    Curran

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    And wheel bearings are adjusted within spec (according to my cheapo fish scale) How would that effect stopping distance?
    Thanks Dan.
     
  7. cruiserdan

    cruiserdan SupportingVendor Emeritus Moderator

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    If the wheel bearings are loose the rotor rocks back and forth, kicking the pads and pistons back in. When you apply the brakes the first "push" has to move the pads back out to contact the rotor but you run out of pedal before it really grabs. Subsequent pumping restores a "normal" pedal until you move out again and knock the pistons back in.
     
  8. Curran

    Curran

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    Ahh, that makes sense. But I doubt that that is the problem. The bearings were with in spec. My current best guess is that the rotors got a bit dirty in the quick exchange ( I was out of break cleaner ) and the shoes aren't getting a good bite.
    It's geting late and dark. I'll give it a look again tomorrow.
    Thanks.
    Curran
     
  9. Cruiserdrew

    Cruiserdrew On the way there SILVER Star

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    I was just going to say that you got grease on the rotors. Clean them up really well with brake cleaner and I'll bet you'll be happy. There is no other reason that a birf swap would affect the braking.
     
  10. IdahoDoug

    IdahoDoug

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    I also favor the "jammed piston" scenario if the brake cleaner doesn't change things. You'll need to really wash them down as well as see if you can rinse the pads.

    DougM
     
  11. ultimauk

    ultimauk

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    "I really didn't mess with the brakes aside from moving them out of the way to get inside the knuckle."

    I suspect this is your problem, possibly you have introduced air into your brake system via a leaky.....?

    Bleed the front brakes, it's cheap, easy, and if I'm wrong, it wouldn't be the first time.
     
  12. IdahoDoug

    IdahoDoug

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    Auk,

    That's a SWAG without the S part. No way moving a brake component with the hose attached would cause something to leak/suck air. If a hose/seal were that badly rotted, it would have gushed every drop of brake fluid out a long time ago.

    DougM
     
  13. ultimauk

    ultimauk

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    Yes sir
     
  14. Radd Cruisers

    Radd Cruisers

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    My guess is grease on the rotors.

    Gets some brake cleaner.
     
  15. Arya Ebrahimi

    Arya Ebrahimi

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    3rd this motion ;p
     
  16. beaner

    beaner

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    you might also check your rear brake pads. but yeah, it's more than likely greasy rotors.
     
  17. Gauge

    Gauge

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    Yea. I agree. I have had this happen to me before as well. Once the grease burns off everything is as good as new. You would be surprised how much a few greasy thumb prints can affect breaking performance.
     
  18. PHAEDRUS

    PHAEDRUS

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    When you backed teh calipers off the pull it off the rotor did you bleed out through the stem or did you just push back in to the reservoir??
    if the brake clean doesnt solve the problem make sure you didnt back some build up in the lines into the master cylinder or into the calipers them selves. a quick bleed will tell you whats going on. if you have pressure at some of the points but not at others chances are a blown seal in the master.
    theis a a ling shot guess and the others are probably right on greasy rotors.
     
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