Goose impersonator disc brakes

[Tootyred]

I come from a time well before the " disc brake". My first car didn't have them even! I predominantly live on the " other side" of the forum, but i hope you modern guys, with your modern ways might help an old timer out.

So, i have a scot scale 640. The problem is the brakes squeel like a goose in a foie gras press. Ive tried alcohol on the rotors and cleaning the pads, but to no avail. I changed the pads, cleaned the rotors and it got better for 5 mins....then its back.

Calipers are not leaking, ive not sprayed it with anything......built and changed about 4 sqillion motorbike pads in my life, including race stuff, so i know the score about not covering them in oil, wd40, saliva etc.

Could it just be crappy shimano pads? Or are the m596 calipers know for being poor? Could it be adjustment?

Are there better pads or a type less likely to squeel?

I dont use it much tbh as its got those wierd boingy boingy forks, but, its so bad im seriously thinking of selling the bike as its an embarrassment to ride!

Any suggestions..?

 

[dyna-ti]

Something is amiss obviously. And squealing is normally down to vibration. So is the centralizing of the calier maybe something to look at ?
Sintered or organic also make a difference. Sintered are known to squeal, though thats maybe just in the wet, though that said my organics start to squeal when wet, but the action of breaking seems to shed the water off the rotor and its stops.

 

[Tootyred]

It certainly gets worst the harder i brake. Light braing fine, pulling up in a hurry.....goose torture.

 

[mdvineng]

Alignment is probably required in the first instance.

 

[2manyoranges]

It's usually contaminated pads.

But sometimes it isn't.

I have one bike with a front 203mm rotor which also has a goose trapped in it. Nothing has so far encouraged the goose to come out. I am going have another go at it this coming weekend - I'll let you know.

Mine is a 203 disc, shimano XT caliper, 183 H Hope lightweight machined brake mount to convert 180 to 203, no washers in the system. I am going to try re-centering the disc and see what happens. Then a stronger brake mount and use a 20mm mount with washers to get clearance. Then change pads after cleaning the disc. Then try a 0.5mm Hope shim on the disc and see if recentering the disc helps. Then buy some earplugs. At least the howling informs idiots walking up the singletrack that we are coming...and fast.

 

[pete_mcc]

What pads you using? Metallic pads will squeal far more than organic. Organic wear faster but are so much nicer.

Alternatively, rather than cleaning your pads, sand them. Cuts through the top layer and removes glaze.

 

[2manyoranges]

What pads you using? Metallic pads will squeal far more than organic. Organic wear faster but are so much nicer.

Alternatively, rather than cleaning your pads, sand them. Cuts through the top layer and removes glaze.

hmm I played with pads and cannot for the life of me remember what I finally put in. I will dig some organic out and see what happens. The brake is mighty powerful, and clearly creates oscillation (hence trapped goose) and it's not fluid contamination.

 

[dyna-ti]

What make/model are the calipers ?. Age ?. Possible the pistons are vibrating.
There can only be a couple of things that can vibrate - Caliper alignment the pads or the pistons. You're used to refitting pads but something isnt lining up squarely or is vibrating. For alignment theres a small alignment tool you can now buy that sits over the rotor and centralizes the caliper before tightening to make it all easy.

 

[2manyoranges]

...mine are newish XT (probably 2018 or 19). I tend to centralise by eye (lining up the rotor with the central seam in the caliper, by looking into the pad ‘hole’ with the pads removed. But good point, I should get out the alignment tool from the Birzman tool box and have a go with that..

 

[Tootyred]

I might take the calipers off and pressure test the seals, im wondering if theres a fine mist coming out the seals. That would explain why it goes when cleaned then comes back gradually later.

They are m596 calipers, with sintered pads. I know these are not the best calipers ( the rear got replaced under warranty as it leaked new out the box, which says something!).

They have been cleaned with brake cleaner, linished, re cleaned, leading edges removed.