After a recent post about this problem have cleaned all parts rotors and new organic pads no leakage spotted by LBS or others. all bolts tight .. still screaming. Next steps? bleed and recheck? brakes are slx and about 2010 is it a known issue or is it new caliper time
TIA john

I always thought it was due to poor calliper to disc alignment ?

Pull lever slowly, watch the rotor betwwen the pads, if it is being pushed by one pad before another the rotor is being deflected and could cause noise.
Lossen caliper mount bolts and move until no deflection, also check both pads move (sticking piston)

Thanks for that. thing is the brake has been fine up till recently was also ok with new pads for 1 ride, will go and check alignment/piston movement
john

As argoose says , check the piston movements as it needs to be equal as poss and apply to the disc at the same time . Do the Hope trick of evening the pistons up by applying the brake and holding the disc against the easy moving piston to force the other to come out and see how sticky/slow stuck it might be.

Are we talking squealing when wet or also when dry?

a bit of copper slip on the back of the pads….

right then checked all above both pistons look to be moving freely, loosened caliper and recentered by holding lever in and moving cal over to even out gaps and piston strike quick spin on road no change,
TGuy in the dry and really screaming ,not a little bit of squeak I could cope with that, will try a little coppa slip soon so thanks all for ideas I am not too hopeful still 😐

BB7s deflect the rotor and don’t squeal (unless it is wet when they might squeal a couple of times), so I wouldn’t think that has anything to do with it.

Organic or sintered pads?

i have always found sintered more likely to scream than organic.

Mine were doing it with a vengeance after a hamfisted bleed this afternoon. Sanded down the pads with fine grade paper and cleaned the rotor with isopropanol alcohol and that’s taken care of it, so can only think there was a little bit of hydraulic fluid on the rotors.

I cured mine by sanding the rotor wearing surfaces using 600 grade wet & dry. Laid the rotor on a flat surface and sanded round the circumference, turned over, did the other side, then clean it with isopropl alcohol.

Sounds familiar.

I have some 2009 SLX brakes and they have recently been doing the same thing with the front being worse than the back.

I have sanded pads, cleaned discs etc. Been very very careful with cleaning but to no avail. New pads are fine for a ride or two then they start to squeal and then scream.

I’m now almost certain it’s a leak as after a month or so the front brake is pulling back further than it used to /should.

I’ve just spend a couple of hours removing and cleaning everything but it all looks fine. Am on holiday next week so will spend some more time stripping it down and see where I get.
I’m on the verge of upgrading kit on the bike so may decide not to bother – I’m going to get Hope Tech V2 Evo’s as replacements.

Insufficient pad bed in can contribute to brake squeal but usually a problem associated with sintered or semi-metallic pads.

Try sanding your rotors down until there’s no trace of any old markings made by previous pads. When pads and rotors bed they mate together. When you replace the pads it is advisable to sand the rotors to reset this pattern or it will take longer to bed the new pads to the rotors.

Trick I used a few times is to wipe muddy/gritty water on rotor at start of ride. This will de-glaze the pads.
Some pads overheat and glaze. Surface is hard black and shining like glass, lot less braking effect too.

If none of the above stops the screaming brakes, think the next step is getting your brake mounts faced.

Thanks all for all the info.
pads are organic and 2 rides old
its was as bad with OEM pads resin
alignment and piston movement seems ok
next step is wet ndry pads and disc then coppa slip and a bleed . will try to fit mates brake to mine or easier swap wheels then test.
Half term next wk so want to ride and not faff.
Ithink its not over yet 🙁
John

Possibly a different brand / type of pads.
Uneven pad movement won’t cause squealing but if the caliper isn’t centred around the disc you can get squealing.

I had the same thing, drove me mad for weeks. In the end I did this:

Clicky

However, equally as important was bedding them in. You need a steep hill so you can build some speed up and do multiple controlled stops, one after another from around 20mph. Took my front brake about 7 stops before enough pad material transferred onto the rotor. Only then did the squealing stop. Also don’t think that dragging the brakes or doing nice slow stops will bed them in, it won’t.

Try this to align caliper to disc, loosen caliper bolts until finger tight, wiggle your caliper to ensure its loose enough. Now elevate the wheel and spin, gently apply your brake until the wheel stops, now hold brake on tight, whilst holding your brake on nip up your caliper bolts to correct tightness.
Your caliper will now be aligned to your disc, if there is any fouling of the disc when you spin the wheel now there may be a bit of distortion on the disc

No no no no no!
That won’t work. Take the pads out and do it properly, by eye! If one piston moves slightly more than the other (and it will) your caliper will not be aligned correctly.

I had exactly the same problem with a new set of XT brakes. I tried everything – eventually I replaced the standard issue pads with superstar Kevlar pads and have not had a problem since. I have now put these pads into my other bike and am v impressed.

bigyinn – Member
No no no no no!
That won’t work. Take the pads out and do it properly, by eye! If one piston moves slightly more than the other (and it will) your caliper will not be aligned correctly.

POSTED 2 DAYS AGO # REPORT-POST

Well it works for me, I do this probably every couple of weeks after i have checked my pads, i am using hope tech m4’s, never had any concerns on the performance of my brakes over the last 18 months.

Now lets look at this scientifically, when you apply your brakes the lever operates a piston forcing the hydraulic medium through the hose to the pressure side of the piston, prior to this happening there may be misalignment of the pistons, however as the pistons under pressure act against the pads and therefore the disc the pressure on either side of the calliper oil gallery will equalise, if the centre line of the disc is aligned with the centre line of the calliper the the pads will act evenly upon the disc, exerting equal pressure on the disc itself

It may exert equal pressure but it the disc is forced off centre by unequal piston movement then that could set up additional stresses and strains in the disc.

i agree with bigyinn, i used to take the pads out and then center the caliper, but i found with more practice it works better to slowly squeeze the brake with the pads in and adjust the caliper until both pads touch at the same time, then tighten up the bolts, seems to work better cheers steve

[/quote]i agree with bigyinn, i used to take the pads out and then center the caliper, but i found with more practice it works better to slowly squeeze the brake with the pads in and adjust the caliper until both pads touch at the same time, then tighten up the bolts, seems to work better cheers steve

Steve, its Bigyinn who`s suggesting taking the pads out, if there is unequal piston movement then,there must be a reason, could this be due to scoring of the piston side or the inside of the cylinder bore, caused by fine grit ingress causing wear and seizing. I sometime think we may be better with a stronger return spring to ensure the piston returns back into the cylinder once the brakes are released.

My Formula Rx SCREAM on longer DH runs on anything other than original Formula pads. So for local riding I stick to generic pads and have some proper ones for bike parks