squealing disc brakes sand the discs ?

swod1

Over the weekend i had a chance to look over my brakes as i ride everywhere and the brakes had started to squeal again for the second time.

Reading a few mtb sites they all pretty much mention sanding the disc with some wetndry to take the shine off the disc.

has anyone else resorted to this as it actually does seem to sort the problem because cleaning the disc with isopropyl just didnt make any difference at all.

Is the squeal more prone to happen when using resin based pads which creates the shine on the disc rotor ?

The Rookie

Really bad idea, you brake on a small layer of pad material deposited on the disc (what bedding is is for) so taking it off again is just silly.

swod1

The Rookie wrote:

Really bad idea, you brake on a small layer of pad material deposited on the disc (what bedding in is for) so taking it off again is just silly.

yes i realised that as after i roughed up the disc, i walked the bike around for a few minutes and dragged the affected brake to re deposit pad material back on to the disc again.

Which seems to have cured it for the time being.

I'm also wondering what pad material is best for my riding as i use the bike for everything getting to work few days a week and weekend rides with mates etc.

I seem to have had more issues with resin pads but never tried sintered, which would be the better option ?

The Rookie

Resin are the better option of the two unless you ride in muddy or gritty conditions which will eat them.

best of both worlds is Kevlar, almost as hard wearing as sintered with many of the benefits of organic.

swod1

The Rookie wrote:

Resin are the better option of the two unless you ride in muddy or gritty conditions which will eat them.

best of both worlds is Kevlar, almost as hard wearing as sintered with many of the benefits of organic.

I have had superstar kevlar red pads before but had issues with them getting glazed too easily more my fault i think, so went back to shimano pads for the time being.

maybe i should try them again.

swod1

I'm still trying to get to the bottom of this but can't seem to find the problem.

I'm wondering if the pistons aren't retracting properly because I can see some of them sticking out a little and this when pressing the brake is causing the noise as it's not a squeal as such more like a squeak this time.

What can I clean round the pistons with, is some isopropyl ok on a cotton bud ?

Anything else I should try/clean ?

kajjal

Check everything is bolted on properly, including the wheel QR/bolt through being tight enough. Also take the wheel off to check the hub bearings are not too tight or too lose and run free.

lpretro1

Often caused by brake not being set up properly- look at the disk when you squeeze lever to see if it is deflecting. If it is then re-centre the brake - esp as you say one piston seems to be a little farther out than the other?

swod1

It's definitely the brake as everything else is fine nothing loose.

It's when you press the brake it happens on both, you can hear the pad make contact with the disc but when you put the brake on full there is the loud squeak noise.

So this must be a sticky piston or something that I can give a clean

The Rookie

No this mustn't and won't be.....if it's only when you are breaking then even if it were sticking the pad would be on the face of the disc anyway! You may have glazed the pads, you may have a mounting issue (Avids?).

swod1

The Rookie wrote:

No this mustn't and won't be.....if it's only when you are breaking then even if it were sticking the pad would be on the face of the disc anyway! You may have glazed the pads, you may have a mounting issue (Avids?).

The brakes are Shimano br-m446 brakes with shimano resin pads and shimano rotors, the front is 180mm disc with shimano post to post adapter.

The brakes are aligned with no rubbing when the wheels are spun.

I could try some replacement pads but only got sintered in my spares box.

The Rookie

Clean up the mountings of both caliper and disc and refit, squealing is a resonance (vibration) so anything that changes the resonance can affect it, Avid's seem more prone than Shimano due to the silly CPS mounting system. Sintered will usually squeal worse than resin as the pad is stiffer so doesn't damp vibration like a resin pad will.

swod1

The Rookie wrote:

Clean up the mountings of both caliper and disc and refit, squealing is a resonance (vibration) so anything that changes the resonance can affect it, Avid's seem more prone than Shimano due to the silly CPS mounting system. Sintered will usually squeal worse than resin as the pad is stiffer so doesn't damp vibration like a resin pad will.

the front brake is worse than the back, is this maybe because i've put a larger disc on the front, i cleaned the mounting holes on the fork leg before putting the adapter and brake caliper on. the longer mounting screws had some strange washers on it one was curved and other was countersunk to fit the other one, made sure the bolts were done up tight.

I've also got a bit of a miss match as the front wheel is centre lock rotor and rear is 6 bolt disc as i had to replace the rear wheel as i broke it.

i was keeping the sintered pads for winter, i do have some superstar kevlar that i thought were glazed but arent that i kept to see if i could reuse them.

swod1

well if anyone is bothered an update to this is i've sorted the back brake for the time being touch wood hopefully and more concerned about the front brake.

I've ordered some new pads to try in it to rule out a pad problem but i supect a slight oil leak in the caliper, the brake is only 2 years old can't be failing already ?

I've cleaned around the pistons with ipa on a cotton bud and the rest of the inside of the brake.

Can anyone answer as i'm unsure cleaning the disc rotor with ipa does it remove the pad material on the disc ?

cooldad

It doesn't matter - clean it and as soon as you ride it'll be back again.

The Rookie

IPA won't remove the layer of pad material anyway - it's not soluble, only sanding would do that.

bazza333

Theses are Shimano brakes but the "strange curved washers" sound like Avid parts

swod1

bazza333 wrote:

Theses are Shimano brakes but the "strange curved washers" sound like Avid parts

The adapter is official shimano came in retail packagaging from crc.

I will have to get a pic up on here.

The Rookie wrote:

IPA won't remove the layer of pad material anyway - it's not soluble, only sanding would do that.

That's what I thought, I've a set of new pads on order. The discs look fine after numerous cleans to try get rid of the noise.

I will try this first and if same thing happens again I'll have to replace the brakes with a new set, seals can't be repaired can they?

The Rookie

Depends on the brakes, but without evidence it's leaking why blame the seals?

Right now it sounds like the callipers are not mounted properly which would explain why they are squealing, photos and let's sort that out first.

paul.skibum

squealing wouldn't come from a leaking caliper - you just would lose effective braking wouldn't you? - The system relies on pressure after all - plus if the caliper is leaking I would expect you to be getting fluid on the disc and then I pretty much guarantee you wouldn't get squealing other than from you the first time you go to stop and nothing happens!

Squealing will be due to misalignment in some form or contamination - rule out the cheapest and then faff with the other. My Shimano brakes squeal if I have spent too long dragging them on long descents with guests.

swod1

Thanks for the help so far, I've got new pads on order from superstar Kevlar ones as I didn't want to waste money on shimano stock pads as they aren't great.

The current pads red Kevlar superstar could be the issue they didn't look glazed so have give them a sand with some wet n dry to see if the cause is this which I suspect and went for a ride to bed them in and all was well but the squeal has returned.

why I ask about the seals is when I checked the pads there were small trace of oil on the back of the pad in a circle pattern in the middle of the pad ?

Taking the pads out I lightly pressed levers and cleaned around the piston seals of each brake, the front brake one of the pistons, one facing the outside edge of the rotor is moving more freely.

Will double check alignment of calipers later and take pictures.

Chunkers1980

This whole saga is quite boring. Have you actually used them for an extended period? Brake problems (if aligned just ok) seem to sort themselves out with extended use.

swod1

Chunkers1980 wrote:

This whole saga is quite boring. Have you actually used them for an extended period? Brake problems (if aligned just ok) seem to sort themselves out with extended use.

Yes i have, i use the bike to ride to work and back as its a short distance and at the weekends so gets ridden more than 4 times a week.

I have put new brake pads in bedded them in fine and no difference at all the front brake has contaminated again, oil on the back of the pads is this normal or leaking seals ?

Through use i've changed pads many times since buying the bike but havent had this much trouble before, it has started since using superstar kelvar pads, they seem to contaminate/glaze too easily.

what are organic compound like for heavy use, i have no problem replacing pads every few months if need be.

cooldad

If they are getting contaminated, it's not the fault of the pads.
It's not normal.

MtbDiyShed

paul.skibum wrote:

squealing wouldn't come from a leaking caliper - you just would lose effective braking wouldn't you? - The system relies on pressure after all - plus if the caliper is leaking I would expect you to be getting fluid on the disc and then I pretty much guarantee you wouldn't get squealing other than from you the first time you go to stop and nothing happens!

Squealing will be due to misalignment in some form or contamination - rule out the cheapest and then faff with the other. My Shimano brakes squeal if I have spent too long dragging them on long descents with guests.

As mentioned squealing is usually contamination pads, scratched rotors or the rotor needs tightening. I had an issue before and tried various things but it kept on squealing and it was down to the budget Avids I had. I replaced those with better quality Elixir 7's and after that I was in heaven!!!

swod1

cooldad wrote:

If they are getting contaminated, it's not the fault of the pads.
It's not normal.

So time for a replacement brake/caliper then i thought as much, was worth a try off new pads.

i wondered if you could buy new seals for the caliper but i guess its not worth the hassle given the price of a new one on crc.

The oil on back of the pads isnt a lot but shouldnt be there should it ?