White 'stuff' on rotor...

Kiblams
Kiblams Posts: 2,423
edited July 2009 in MTB workshop & tech
I have recenlty noticed a severe reduction of power from my Avid BB5 disc brake; being as lazy as I am and the power still being more powerful than most V-brakes I have used I simply let it be.

However was out riding in the thunderstorm this morning and the braking power pretty much dropped off completly! :? and after holding the brake down for about 10seconds down a hill I noticed thatthere was odd white 'stuff' on the rotor which washed off soon after by the rain while I was trying to figure out what it was.

Any one got any idea what it is? I will be replacing the pads and cleaning the rotor with rubbing alcohol as soon as I get to the shops, but I am very curious if anyone can enlighten me? as it may tell me what has gone wrong and how to prevent it in the future.
HandsomeDog - OrangeCommuter

Comments

  • Daz555
    Daz555 Posts: 3,976
    Residue from cleaning detergents would be my guess.
    You only need two tools: WD40 and Duck Tape.
    If it doesn't move and should, use the WD40.
    If it shouldn't move and does, use the tape.
  • Kiblams
    Kiblams Posts: 2,423
    The bike never comes in the house and how would cleaning detergents appear on the rotor half way through a country ride? :?
    HandsomeDog - OrangeCommuter
  • bails87
    bails87 Posts: 12,998
    If/when you last cleaned your bike, maybe some bubbles got left on the forks and dried, leaving soapy residue? it's possible that the rain washed the soapy stuff down onto the brakes.
    MTB/CX

    "As I said last time, it won't happen again."
  • Kiblams
    Kiblams Posts: 2,423
    bails87 wrote:
    If/when you last cleaned your bike, maybe some bubbles got left on the forks and dried, leaving soapy residue? it's possible that the rain washed the soapy stuff down onto the brakes.

    That would be possible if I used soap on my bike :wink:

    I just use warm water and a brush followed by a cloth to dry and then lube.

    It's not like I even leave it outside at work anymore, so I don't think it could even have been sabotaged :?
    HandsomeDog - OrangeCommuter
  • bails87
    bails87 Posts: 12,998
    Hmm foiled! I was just explaining what I think the guy above meant. I dont have a clue then!

    How much pad have you got left? Could it be that they've worn right through the braking surface? Gone through to either the stuff that holds the pad material to the backing plate (if this exists) or down to the backing plate itself?
    MTB/CX

    "As I said last time, it won't happen again."
  • nicklouse
    nicklouse Posts: 50,673
    what lube?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Kiblams
    Kiblams Posts: 2,423
    nicklouse wrote:
    what lube?

    Finish Line Cross Country WET Lubricant.

    i just swapped out the rotor in the off chance that it would make a difference and it has. A massive difference! :D I get the crazy scary fork flex under breaking again now! :?

    Thanks for your ideas guys, I think I will get myself some rubbing alcohol as I obviously got a contamination from somewhere. Probably the front hub bearings knowing me :wink: although I have never greased/lubed the front hub...
    HandsomeDog - OrangeCommuter

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