Howling disc brakes

trickytree1984

Hi. I have Shimano hydraulic disc system on my road bike. I had an issue with very very loud brakes (embarrassingly load) last year and tried everything. This year, to nip it in the bud, I bought new discs and new pads. Shimano ice tech rotors and resin pads (like for like replacement)

I went through the bedding in procedure and all seemed better. Anyway, after washing the bike, I used muck of disc cleaner to ensure no contamination. Next ride, TERRIBLE squealing.

Now I've followed some online advice to sand the rotor. I've done this but I'm worried I've made a massive mistake? I've also cleaned up the pads again using a blob of swarfega and rubbing together. They look better.

Where am I going wrong? Alignment looks ok. Someone said copper grease between the piston and pad?

trickytree1984

oxoman wrote:

One word Swarfega, New pads required I suspect. Never ever put anything on disc pads. Clean discs with proper disc cleaner. I have never ever cleaned my discs or pads. I have however used copperslip on the back of the discs.

The swarfega was an attempted fix. The pads were brand new and had nothing on ever. Tried muc off disc cleaner. Made it worse. Same issue on two sets of brand new pads and discs.

I'm.wondering if it's the wheels that just resonate the vibrations

cycleclinic

my wifes bike has this issue. I have new rotors, pads and caliper under warranty as madsion accepted they were leaking.

this has been an ongoing issue. we are now on our third R785 caliper and she hardly ride the bike because it always squeals.

if you are going to clean the pads iso propyl alcohol is what you should use but really dont clean them. if they are contaminated bin them.

you may have the same problem a leaky caliper.

grenw

If it's in the wet then they all tend to do this in my opinion - give them a couple of short sharp blasts and they tend to quiet down. This is based on a few years on mountain biking with Shimano, Formula and Sram brakes. My current road bike with diascs hardly makes a sound but that's just because I ride less in the wet and the brakes stay cleaner.

Have always used IP alcohol to clean the discs - a quick wipe and binned any pads that I thought were contaminated.

Have heard that putting some grease/anti-seize on the back of the pads (never let anything touch the pads themselves) can help to stop any vibrations resonating into the bike. Not tried it myself though.

trickytree1984

thecycleclinic wrote:

my wifes bike has this issue. I have new rotors, pads and caliper under warranty as madsion accepted they were leaking.

this has been an ongoing issue. we are now on our third R785 caliper and she hardly ride the bike because it always squeals.

if you are going to clean the pads iso propyl alcohol is what you should use but really dont clean them. if they are contaminated bin them.

you may have the same problem a leaky caliper.

Thanks

I really hope its not a leaky caliper. Both front and back are doing it and have done it from new. Bike is only a year old and ridden 1 winter.

trickytree1984

GrenW wrote:

If it's in the wet then they all tend to do this in my opinion - give them a couple of short sharp blasts and they tend to quiet down. This is based on a few years on mountain biking with Shimano, Formula and Sram brakes. My current road bike with diascs hardly makes a sound but that's just because I ride less in the wet and the brakes stay cleaner.

Have always used IP alcohol to clean the discs - a quick wipe and binned any pads that I thought were contaminated.

Have heard that putting some grease/anti-seize on the back of the pads (never let anything touch the pads themselves) can help to stop any vibrations resonating into the bike. Not tried it myself though.

It is the wet and its at low speed. Initial braking phase is ok, its as i come to a stop. Its so loud its dangerous. I'm scared to brake in certain situations because it scares people to death!!! I nearly caused an accident with horses the other day, and the old lady with her dog looked like she had seen a zombie.

I think i will try copper slip

veronese68

I suspect contamination is the problem. Don't use anything near the pads, don't use disc brake cleaner, swarfega, washing up liquid or anything. If cleaning the bike keep all chemicals away from the discs and pads, even degreasing type fluids. Once you've finished rinse thoroughly with water. If you have to clean the discs use isopropyl alcohol as mentioned above. A small amount of copper slip on the back of the pads may help, just make sure you don't get any on the braking surface of course.

lesfirth

I have no experience of bike disc brakes but on cars putting some copperslip on the back of the pad is done every time they are fitted. In problem cases putting a small chamfer on the leading edge the pad with a file often stops any noise.

dee4life2005

I've been having exactly that issue with my Shimano RS785 hydraullic calipers. Tried everything as mentioned, sanding rotors/pads, using fairy liquid, IPA, even new pads (after a rotor clean) didn't cure it for long.

As a last resort, after reading on line, I gave everything a thorough clean and then with the rotors and pads still off the bike I gave them a very brief (talking a few seconds) going over with my mini kitchen blowtorch. That seems to have managed to burn off whatever contamination was still present as they've been quiet since (120 miles so far) - except for the first brake application of the day (thinking that's just because the rotors are cold - and maybe have condensation from the bike living in the shed). Did have to bed them in again though, but the braking force is back to being insanely good again.

keef66

Interestingly the front discs on my wife's Focus, - car not bike, - squeal like a stuck pig when the weather is damp. Silent in the dry and when it's properly wet, but if it's cool and foggy, or just drizzling, they shreik. Tried different pads, replaced the discs, copperslip on the backs of the pads every time.

And my A1 does it at the back but only when reversing. Odd.

trickytree1984

dee4life2005 wrote:

I've been having exactly that issue with my Shimano RS785 hydraullic calipers. Tried everything as mentioned, sanding rotors/pads, using fairy liquid, IPA, even new pads (after a rotor clean) didn't cure it for long.

As a last resort, after reading on line, I gave everything a thorough clean and then with the rotors and pads still off the bike I gave them a very brief (talking a few seconds) going over with my mini kitchen blowtorch. That seems to have managed to burn off whatever contamination was still present as they've been quiet since (120 miles so far) - except for the first brake application of the day (thinking that's just because the rotors are cold - and maybe have condensation from the bike living in the shed). Did have to bed them in again though, but the braking force is back to being insanely good again.

I’ve tried everything except the blow torch. This is next!

agentorange88

blow torch is a common MTB solution. can use the torch or strong camping gas stove flame. its more burning off any surface contminations than getting the disc hot. its usual for a slight bluing colour to the disc.
Its possible to do the pads but this takes more care.

cooldad

The biggest problem with disc brakes is the idiot doing random things to them.

Rinse with water when washing the bike. Do nothing else.
Clean new rotors with IPA,

fat daddy

the shimano brakes that came on my Hybrid were howlers ... I tried everything .. and considering I run 2 commercials, a Santa Cruz a cannonade and a speech with Various disc setups, its not as it I dont know how they "should" be working.

sh1tehole things would just start to howl every 4-5 days even if I didn't ride the bike in that time

recent tried the very last thing I could think of other than rebuild them and that was to spank out £40 on a pair of front and back + rotors Clarkes units ..... yeah, that fixed it and hasn't reduced braking in anyway

Now I guess its time to rebuild the Shimano shote and see whats wrong with them .. must be a fine leak at the piston or something