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Road disc brake problems

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  • August 1, 2017 at 9:47 am #27431
    SteeveB

    I need some help with my disc brakes!

    I am having a lot of problems with contamination of pads/rotors. Not really sure why but i now have two noise and vibration devices rather than brakes. The brakes are RS805’s from last year.

    Last night i sanded all the crap off the rotors. Got them nice and shiny. Sanded the pads  (they are the standard shimano ones that come with the brakes). Got them quite shiny. Cleaned everything with isopropyl alcohol (again). All went bad  when i cycled to work.

    Fixing the rotors is easy; just need sandpaper and elbow grease. But the pads are more of a problem.

    I have seen on some forums that people heat their pads to clean them. Anyone got any tips on this – how to do it? what temp to use? Does it work?

    Dont want to buy more pads if i can help it. Last lot are only a few months old.

    Never had a single problem with my MTB discs but the road ones are turning out to be a pain.

    SAB

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  • August 2, 2017 at 11:45 am #898599
    0
    Jack Osbourne snr

    IanEdward wrote:

    IanEdward wrote:

    The advice from kev-s is good.

    Oi! I said all that first 

    Ooops. Sorry!

    The advice from IanEdward is good too!

    August 2, 2017 at 11:27 am #898597
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    StraelGuy

    I have the same issue with

    I have the same issue with mine. Part of the problem is material related. Car brake discs are made of grey iron which has an extremely high self-damping ability which is why they rarely make any noise. Bike rotors are made of stainless steel which has a much lower self-damping ability and so are very prone to screaching in the wet. Unfortunately, at bike rotor thicknesses, grey iron is too fragile to make rotors out of indecision.

    August 2, 2017 at 11:17 am #898595
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    IanEdward

    Quote:

    The advice from kev-s is good.

    Oi! I said all that first 

    I think sanding rotors is perfectly OK and seems to be an accepted maintenance thing with disc rotors, more for when you are changing pads (especially if you are changing compounds) as the rotor will apparently hold onto pad material from the old pads which doesn’t always play well with new pads.

    Also something to do with bad bedding in which can deposit differing amounts of pad material around the disc which can set up a sort of stick/slip reaction which can cause squeel.

    Could anyone tell I’ve been trying to cure a set of squeeling discs recently? My next road bike will be back to rim brakes, I can tell you that much… no

    August 2, 2017 at 8:03 am #898593
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    StraelGuy

    I use their discs and pads
    I use their discs and pads with my Spyres but I’m about to fit 805 calipers and they don’t seem to do the pads yet.

    August 2, 2017 at 7:48 am #898591
    0
    Jack Osbourne snr

     

     

    The advice from kev-s is good.

     

    Bin the pads. Trying to decontaminate is a waste of effort.

    Sintered pads last longer and are less prone to contamination (but not immune).

    If you go to Disco Brakes, you can get sintered pads for a fraction of the Shimano organic pad price. 

    http://www.discobrakes.com

     

    I’ve used them for both Avid and TRP discs for several years and love them. 

    August 2, 2017 at 6:58 am #898589
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    kev-s

    It amazes me what people will

    It amazes me what people will do to a set of contaminated pads!!

     

    Chuck them in the bin, clean your rotors with isopro alcohol (dont sand them) clean the calipers with isopro alcohol, check for any obvious signs of leakage from the pistons, where the two caliper halfs join together and brake hose joints

     

    Fit some new cheap pads, bed them in and see if they get contaminated, if they do then you have a leaking caliper, you may not be able to see the leak but you will have one

     

    If in warranty contact the shop you bought them from or the distro who import them and they will ask for it back and do a pressure test on the caliper

     

    This is the process i went through with a Shimano XT caliper

     

    The distro sent me a brand new caliper and pads and no more leaks!

    August 2, 2017 at 6:20 am #898587
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    simonmb

    gonedownhill wrote:

    gonedownhill wrote:
    put the pads face up in a small puddle of isopropyl, set it alight

    I don’t know. In my experience, setting fire to things rarely ends well.

    August 2, 2017 at 6:10 am #898585
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    madcarew

    I don’t know a whole lot

    I don’t know a whole lot about disc brakes, but personally I’d be really wary about sanding the rotors to clean them. If they’re ‘contaminated’ it will only be surface as oils etc won’t soak in to the metal, so just take the wheel out, wipe it with a degreaser until shiny, wash with soap and water and put back on the bike. Sanding with coars (,400 grit sand paper) I think would have a high chance of affecting brake performance, and increase likelihood of contamination of the pads. IMO. 

    With most brakes (cars, motor bike etc) one the pads are contaminated with oil, it’s something of a fools errand to try to decontaminate them (or so my engineer Dad told me)

    August 1, 2017 at 5:25 pm #898583
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    IanEdward

    I’m a little out of touch

    I’m a little out of touch with Shimano brakes, but I think leaking callipers causing contamination was a fairly well recognised problem.

    It’ll drive you crazy because apparently the leak is small enough that you won’t be able to trace it.

    In my experience life is too short to try and recover contaminated pads. Bin pads, buy new ones and clean everything thoroughly before refitting.

    Spend the next couple of weeks being hyper careful about oiling the bike etc. so you can be sure you haven’t contaminated the pads yourself. If they develop the same problem it’s probably worth considering that they’re leaking. Raise it sooner rather than later with the shop you bought them from so you have a better chance of raising a warranty claim.

    If you search the google term ‘singletrackworld: leaking shimano’ you should probably find a thread where someone identified the issue and a possible fix (replacement o-rings to fit between the calliper halves).

    This is why I’ve not bought Shimano brakes in the last couple of years, my dad’s had two duff sets…

    August 1, 2017 at 4:19 pm #898581
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    SteeveB
    Butty wrote:
    Vibration sounds like large disc run-out from being warped or lumpy deposits.

    Pad wise, I only get squealing in wet weather if I haven’t cleaned the pads for 3/6 months.

    I rub the pad faces against each other under the tap with some washing-up liquid as a degreaser.

    Keep rubbing until there is no mucky paste left.

    The pads then get wiped with alcohol and refitted.

    I’d be concerned that uncontolled heat may detach the pad material from the carrier.

     

    will try this tonight. sounds like a cheap solution to my problem

    August 1, 2017 at 4:18 pm #898579
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    SteeveB
    Mungecrundle wrote:
    I too was a fan of a good scrub with a wire brush and alcohol, but then I found these, and at the price, contaminated pads get one chance at rehab and then get binned if they fail to clean up.

    HTH

     

    Wow, that is a good price. way cheaper than the shimano’s. I might try them as replacements. cant go wrong at that price.

    August 1, 2017 at 4:17 pm #898577
    0
    SteeveB

    hi, thanks for the feedback.

    hi, thanks for the feedback. i dont really know how the pads/rotors are getting contaminated. something is bad is happening.

    I do wonder if my front brake has a slow oil leak. maybe a small amount is coming out and contaminating the pads. really hard to tell if this is happening as no drops of oil are visible anywhere.

    the back one went bad last week when cycling to work in really heavy rain. but dont know what happened. 

     

    Will clean the rotors again tonight when i get home. how clean do they need to be? i sanded them clean last night which took a while. hopefully they wont be so bad.

    to clean the pads – how do i know if they are clean enough? should there be no black particles on the surface at all? i sanded them yesterday but couldnt get all the black crap off, there were still some bits left. i guess that is what recontaminated my rotors this morning.

    will try some of the tips above to clean pads again tonight.

    Listen out for me on the way home from work – you will be able to hear me from wherever you are in the the country!

    August 1, 2017 at 2:23 pm #898575
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    CXR94Di2

    Move into sintered pads, much
    Move onto sintered pads, much much quieter.

    August 1, 2017 at 11:30 am #898573
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    Jimmy Ray Will

    Um, sounds like your pads are

    Um, sounds like your pads are contaminated. Rubbing them ain’t going to help with a serious contamination.

    As mentioned, work out what is contaminating them, stop that happening again, purchase new pads. Enjoy nice brakes.

    I completely messed up on teh MTB the other week. Had a bit of contamination in pads from a bit of gt85. Thought I’d just burn through that no problem… a few draggy and hard stops will get that sorted. I was wrong. The noise got worse, the braking less effective… I squeezed harer and harder. 

    Turns out, my squeezing had exposed a previously undiagnosed crushed o-ring, and I had forced fluid out and onto the discs and pads. 

    Lesson learnt. These days I am very careful to not let any cleaning substance near the pads, and will clean the rotors with alcohol based spray post any cleaning / maintenance as a matter of course.

    DIsc brakes are sensitive little beggars in my experience. 

    August 1, 2017 at 11:25 am #898571
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    Mungecrundle

    I too was a fan of a good

    I too was a fan of a good scrub with a wire brush and alcohol, but then I found these, and at the price, contaminated pads get one chance at rehab and then get binned if they fail to clean up.

    HTH

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