ongoing squealing disc brakes

mkread
mkread Posts: 4
Hi

Both my wife's bike and mine suffer from squealing disc brakes and sometime associated poor braking.

We've repeatedly cleaned rotors (using specific cleaners and 99% alcohol), cleaned pads, sanded pads, replaced pads. But within a few rides they are often back squealing.

I can usually "burn" mine off during a ride using them on a steep descent, after that they are fine and good at braking for the rest of the ride but the next start of a ride they are back howling. This happens even if I just put the bike away without cleaning etc. Just an overnight in the shed and they are back making noise.

We're careful with lubricant (use covers if applying) and it's not as though it's just the back brake. It's only my front at the moment that is making a noise.

They are ultegra brakes, we mainly use shimano resin pads, but have also tried gorilla pads. We had the rotors changed on my wife's back (140 to 160mm) but noise back after a few rides.

Historically my wife's have been worse. Mine we're OK for a while but not so much lately. I'm heavier and can apply the brake harder. When we've changed pads we follow a bedding in procedure.

At a bit of a loss and it's costly keep changing pads! (but that's the only thing that works for a bit). One LBS suggested shimano pads were not so great, did something change with their pads during lockdown. Are there fakes going around even!

We've always stored the bikes in a cold but well ventilated shed. Mine have mainly been an issue in the last 3-6 months and were fine for the 18-24 months prior.

Any suggestions? Thanks,
Mike

Comments

  • beansnikpoh
    beansnikpoh Posts: 1,533
    Even in dry conditions?

    Mine honk like a flock of angry geese in the wet, but are silent when it's dry.

    Weird that they were fine for 2 years and have suddenly got worse. Everything else OK? Rotors ok? (you don't say you've replaced the rotors). Have you bled the brakes? Leaking brake fluid may be contaminating the pads if the noise goes away and then comes back again. Do the pistons in the caliper move and retract freely and evenly?
  • mkread
    mkread Posts: 4
    yeah even in dry (indeed mostly in the dry as we avoid the rain if poss :smile: .

    Everything OK as far as I can tell (but then again it cant be :smile: ) . Wife's bike has new rotors, new pads, started squealing after a couple of rides. Both bike's had brakes bled at service. Mine don't feel spongy.

    Had thought about leaking brake fluid, but would have thought that would be easy to spot and to have leaks on brakes on both bikes seems a stretch. The guy who serviced my wife's bike couldn't spot any leaks.

    What's the best way to detect a leak?

    Pistons seem to move OK.

  • trevor.hall12
    trevor.hall12 Posts: 448
    Can try taking the pads out and stuff them with paper towel overnight ,that woukd show any little leaks ,take care not to pull the levers .
    Only other suggestion I would make is if tge discs have been checked for warping ,or if you suffer from them rubbing anytime .
  • First.Aspect
    First.Aspect Posts: 15,827
    edited May 2022
    Could it be alignment?
  • woodywmb
    woodywmb Posts: 669
    Sounds like fluid coming through from the back of the pistons. You can test for this by continually braking while the bike is on a stand. Alternatively the discs could be contaminated (possibly from a piston leak). Scrub the rotor with meths. It will dry immediately. Then use a blowtorch on it.
    As someone suggested the problem could be alignment. Change the caliper alignment in increments with the bike upside down. Try various positions and also unequal gaps. It's a laborious procedure but can work, even though there's no logic attached!!
  • mkread
    mkread Posts: 4
    Thanks all, will try and narrow it down!
  • rwoofer
    rwoofer Posts: 222
    I have exactly the same issue and haven't been able to figure it out for a long while. As you say the only way I get good performance is a prolonged, steep downhill which makes them good for the rest of the ride. Curiously on one of my DB bikes it suddenly stopped after one particularly big downhill and has been fine ever since.
  • wongataa
    wongataa Posts: 1,001
    Sometimes you need multiple hard applications of the brakes in one ride to stop the noises I have found. If you can do this during several rides even better.
  • lesfirth
    lesfirth Posts: 1,382
    Mkread, welcome to the forum. One of the problems on this forum is sorting out the sound advise from the rest of the nonsense ( being polite ) replies .
    I doubt very much that you have a fluid leak or an alignment problem and I certainly would not suggest that you use a blow torch on your bike!

    My fix was using some fine sandpaper or " wet or dry" paper to clean the braking surfaces on the disc . No amount of solvent cleaner will remove the film of pad material that sticks to the disc. Then put the sandpaper on a flat surface and gently rub the pad surfaces on it so that the pads have a uniform matt appearance.
    Reassemble and go and do lots of HARD braking.

    Disc brakes like to be used hard. If you live in a flat area or you are a light weight ,cautious rider, you need to do a bit of hard braking from time to time just to keep your brakes happy.

    Changing from 140 to 160 discs could make the problem worse. 160s will not have to work as hard.