Forum home Mountain biking forum MTB workshop & tech

Disk Brake Power Loss

CharlieV453CharlieV453 Posts: 100
edited October 2017 in MTB workshop & tech
Hi there!
I know the story of squeaky brakes and if you contaminate them they squeal and lose power. However, my brakes were working fine and I hadn't recently cleaned my chain. After locking up my bike and leaving it for a few hours, the brakes had lost power, started squealing and when i wiped my clean finger over the disk it came out dirty.

Does anyone know why and how this could happen.
I do know how to fix it however but the repetition is getting irritating
Thanks

Posts

  • robertpbrobertpb Posts: 1,866
    Go to Halfords and buy a can of brake cleaner, it's cheaper than buying bike specific cleaner.
    Now where's that "Get Out of Crash Free Card"
  • FishFishFishFish Posts: 2,152
    No reason why the brakes should not be dirty - could just be dust. It is cold and humid at the moment which would hold the dust. Look up bedding the brakes in by going down a slope and going hard on the brakes. Alt - and I do this myself - remove the pads and score them with the edge of a file. I do that on the principle that it stops the pad exciting a standing wave in the disk. Seems to work anyway. Try Kevlar pads in future or best of all -= give up braking.
    ...take your pickelf on your holibobs.... :D

    jeez :roll:
  • FishFishFishFish Posts: 2,152
    ...and clean the disk with Methylated Spirit or denatured alcohol as it is alternatively called. If you are buying it from the chemist then try not to look too rough.
    ...take your pickelf on your holibobs.... :D

    jeez :roll:
  • The RookieThe Rookie Posts: 27,748
    Do NOT use a non bike brake cleaner, the brakes on bikes don't get hot enough to burn off the residue. Rubbing alcohol is best.
  • Thank you all for your help. I have tried the methods given to me and they work well. The problem is now fixed and my brakes are working well. Thanks
  • FishFish wrote:
    No reason why the brakes should not be dirty - could just be dust. It is cold and humid at the moment which would hold the dust. Look up bedding the brakes in by going down a slope and going hard on the brakes. Alt - and I do this myself - remove the pads and score them with the edge of a file. I do that on the principle that it stops the pad exciting a standing wave in the disk. Seems to work anyway. Try Kevlar pads in future or best of all -= give up braking.

    Thank FishFish for your help. The brake pads weren't new enough to require bedding in and weren't old enough to need replacing though but the idea with a file sounds like a good idea. Thanks
  • FishFishFishFish Posts: 2,152
    I'll send you one inside a cake.
    ...take your pickelf on your holibobs.... :D

    jeez :roll:
  • I have also noticed whenever I clean them and put them back on the bike and start braking they instantly become dirty and glazed but how can this be possible if both the rotor and pads are clean?
  • LagrangeLagrange Posts: 652
    Coulds be brake dust, caused by wearing - have a look round the disks on your car for example.
  • The RookieThe Rookie Posts: 27,748
    They can't instantly become glazed, hat requires heat, they may instantly become something but it IS NOT glazed!
  • cooldadcooldad Posts: 32,601
    99.9876545668899% of brake problems are caused by random uneeded faffing
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Yes have just been told it is contaminated not glazed but the surface looks similar so I got confused. Sorry! They do continually become contaminated though. I have been told this could be dirt trapped in the gaps of the brake rotor but I have thoroughly cleaned it twice. Another possibility I have been told about is that my brakes are "misting". I think this is when there is a leak and the oil goes onto the rotor every time you pull the rotor. This sounds highly likley. Does anyone know a fix for this? Thanks
  • cooldadcooldad Posts: 32,601
    Do you really need 2 threads on the same thing?
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • cooldadcooldad Posts: 32,601
    Rebuild the calipers if you can get new seals, or replace. But I doubt that's the problem.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • The RookieThe Rookie Posts: 27,748
    You'll probably find the contamination is soaked into the pad, it's more than a quick wipe over to get the contamination out, you can clean the surface but as soon as you use them it will come back out.
Sign In or Register to comment.