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  1. #1
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    Random Fading and Noise?

    Hey

    I was out of town riding for a few days up north (Olympia Washington) and while i was there, my brakes (avid ultimate 7's) started fading (not like getting squishy, but power wise) at first they were working great, but on about the 3rd day of riding up there i got on my bike and was cruising and when i hit the brakes they started just feeling really powerless. they made a wierd loud vibration noise like the pads were gripping for a second and then slipping repeatedly. I think that is why they were making the vibration noise. but anyways, they kept doing that so i just decided to quit trying to get the noise to stop and put it down. when i got back on it later the noise wasnt there, but the brakes just barely had any power whatsoever. it was really wierd because it wasnt just the front brakes, but also the rear. So my question is, what do you guys think that this random loss of power and noise is being caused by? could it be because of the more humidity, and wet weather in washington?
    also another thing that i may note is that my friend at one point got WD-40 on his mechanical disc brake and it did kind of the same thing, but i dont see how i could have gotten any oil on my brakes at all. i tried cleaning the brakes with isopropyl alcohol but still i am having no luck with them. Could the brake fluid be leaking through the caliper and possibly gotten on the pads? if so, then could it be because of the altitude change? (i believe the pressure decreases going to washing from Utah which would be a weird reason for them to be leaking because of altitude)

    So anyways, what are your thoughts because i really dont know what causes hydraulic disc brake fading and failure like this.
    Thanks in advance!
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  2. #2
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    Reputation: SteveUK's Avatar
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    If you've gotten oil, especially DOT, onto the pads, then you're almost certain to be finding dark streaks on the rotor. Brake dust from the pads mixes with the oil to create a tacky residue which will stick to the rotors and leave a gummy glaze on the surface of the pad compound. Even if you can't find evidence on the rotors, take the pads out of the caliper and inspect the interior for wetness. There should be absolutely no sign of fluid.

    As wordy as it is, your description is pretty vague. What had you been doing when the brakes started working up? Any prolonged descents? Or did it occur after a long period without using them?

    Have you double checked the caliper alignment and all fitting bolts?
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  3. #3
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    i just barely got the bike about 5 -6 months ago, but it hasnt been used much. i do know for a fact that they are aligned properly, and that the brakes are already broken in.
    When i noticed the fading was right after just riding around up in the mountians nearby (no prolonged descents) just riding in some wet clay and mud sort of terrain. i got back, washed the brakes off with water and went in for the night. The next day i was just riding around and everything was all good and then me and my friend went inside for some food while everyone else was working on their quads. when we came outside the brakes were alright for about 5 more minutes after just cruising around on dirt/grass and they started to make the noise. i believe that one of the other guys was putting chain lube on his quad in the area (not too close, but near) of where we put our bikes. he may have gotten some overspray on my bike but i doubt it because the bike my friend was riding was just as close (if not closer) to the guys quad than mine was and the other bike is having no issues. i will pull out the pads and check everything out and i will try to figure out what is going on. it may be because of the lube (i dont really think so, but i cant think of anything else) and i may have leak in the caliper by the pistons as well so i will have to check it out.
    anyways, if it does end up being the lube, do you guys have any idea on how i could get it out of the pads and/or rotors?
    Thanks!
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  4. #4
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    Here are some pics.. i dont think that they look bad, but i am not sure, you tell me..

    Front pads (on these the inner bottom part looks a little like it is worn down a little more maybe. could they be out of alignment?)


    Fronts again:


    One of the rears (what do you think?)


    Rear again:


    Front rotor:


    Rear rotor:


    Well everyone, what do you think about these?
    Thanks!
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  5. #5
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    Anyone?? i think that maybe it was just a temporary thing because so far the front brakes are getting back their strength as i use them more, but the rear arent. i think i may just need to use the rear brakes until they work better again. either way, if they dont get full strength back, what do you guys think?
    Thanks!
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  6. #6
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    i had a similar problem. my brakes had no stopping power after engine parts cleaner was sprayed onto my brake pads.

    this is what i did:

    use rubbing alcohol on the rotors. dont touch the rotors with your bare hands because the oils on your hands can slightly mess up the pads too

    take your brake pads out and bake them in the oven. i put them on a sheet of tin foil with a cookie sheet under. i baked them 350 for about 45 min.

    after this i replaced the pads in the bike after cooling and my braking strength came back. i baked them once more at 375 for 45 min and i had original stopping power.

    if all else fails, try baking pads. or new pads.

  7. #7
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    Alright, thanks a bunch man! I've never heard of that one before so yeah if all else fails I will try baking them for sure!!
    Thanks again!
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  8. #8
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    Just be safe and get new pads. I don't think its a good idea to cook and vaporize petrochemicals in the oven where food goes.

  9. #9
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    Agree with not using the oven.
    But I have cooked off my pads very carefully using a small propane torch set on super low.
    I lay the pads on a vise, and it acts as a heat sink so the backing doesn't get too hot and melt the glue, then take the torch on low to the pad surface and feather the flame around until it starts to smoke a bit. Take the flame away for a second, then repeat that until they no longer smoke.
    I have brought some pads back to life that were seriously contaminated with oils and degreasers. Brakes worked great afterwards.
    If there is bad contamination I will also remove the rotors from the hub and clean with 99% alcohol......then sand with 120-220 grit, then clean again with alcohol.
    this process requires everything to be bed in again, but has resulted in like new brakes everytime for me.
    Look, whatever happens, don't fight the mountain.

  10. #10
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    Alright! Thanks a bunch! I will have to try it.. Does it differ between different brands of pads / rotors? Just wondering because I dont know if they are made different or something.
    Thanks!
    Hey guys! Don't bother asking questions on MTBR! If your lucky you may just get a straight answer! Thanks for the support!

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