After a few weeks storing my bike upside-down awaiting a new wheel, my SLX brakes are suffering from a horrendous case of brake squeal, both front & back. My first attempt was to clean everything with 99% isopropyl alcohol and sand & flame the pads, but the silence only lasted 5 minutes and then the choo-choo train came back down the trail. Rotors look like they are running true and I’ve checked all the rotor & caliper bolts; apart from the noise they are working well.

Next step is to replace the pads but just wondering if replacing rotors is necessary as well? I understand the pads can absorb contaminants but I presume that a good alcohol clean will be sufficient for the rotors?

I’ve had a fair amount of success just cleaning the rotors (very carefully) with IPA. Need to get all the grooves as well, anywhere there might be some oil.

I’ve never managed to resurrect pads though.

I’d say you’re probably best to replace the entire bike.

What oldandpastit said, I’ve had success with just thoroughly cleaning the rotors with alcohol, shut them up a treat!

Pop the wheel and pads out and carefully clean the inside of the calliper with a degreaser – Fairy washing up liquid actually works well if you don’t have any Finish Line.

Clean the pads using a similar technique whilst rubbing them against each other….really hot water helps.

Clean the rotor surface as best you can with the degreaser.

Bob the over onto 160c. Stick the pads and discs in the oven for 15 mins, pads face down on a grill tray. Remove them from the oven and whilst still hot, spray with degreaser and allow to evaporate…don’t be afraid of a little flame.

Reinstall and bed back in.

Worked perfectly for all of my HOWLING XTRs (3 sets) for a few months until I got sick of their temperamental “will they work, wont they work?!” nature and got rid of them.

Is it really so bad that it’s worth all the faff?

I’d just ride it and forget about the noise!!

You need to remove the pad compound that’s embedded into the very fine grooves of the rotor. Use emery cloth or wire wool. Then clean thoroughly with IPA afterwards.

Lay some sand paper (something like grit 180) on a flat surface and rub the pads onto it. Don’t bother baking pads unless you’re quite sure they’ve got brake fluid/oil on them, but even then I’d suggest you bin them – and if they have got oil/fluid on them, you’d better figure out why, e.g. if you’ve got a leaking piston seal.

Also make sure your caliper, and more importantly the pistons are completely parallel with the rotor.

What pads are you using? Have had problems with Uber sintered pads and switching to other ebay versions have been fine with no squeal or cleaning required.

Short answer. Yes.
Tried everything with wife’s bike including scrubbing the disks clean. Nothing worked. Disks are not huge money though so no real drama

The Hydros on my Arkose have been screaming since I started riding it again (been off it over the summer as use it as a winter bike)
I followed the advice in an article by the guy who developed Avids brakes – he suggested taking the disks off and sanding the grooves out with fine sandpaper (on a block – keep everything flat)
Coupled with new (resin rather than sintered) pads the rear brake is now silent, and the front brake only squeaks a tiny bit when first used (still on sintered pads)

Just chuck some muddy water on the brakes and ride them down a big hill a few times, it’s much simpler/easier/quicker than faffing around cooking pads and sanding discs, unless of course you like doing that kind of thing.

For the first time in years I’ve got a howling back Deore brake and all the usual tricks are not working. Suspect a leaking calliper and I’ve tried pushing them out for a good clean but they are still rubbing on the disc. Funny thing is, it’s noisy only when coasting and not pedalling

it really so bad that it’s worth all the faff?

yep have this problem on my youngest’s hardtail with slx = and after swopping out pads, cleaning disk, checking all line up still there and she hates it – maybe need bedding in properly 🙁

sand the rotors

The rear brake of my SLX set (resin pads) squealed from day one and continued to squeal even after I changed the rotor. There were some dire warnings on here suggesting that Shimano brakes were pants and leaked oil, but I could find no indication of this. I replaced the pads after they’d worn out (they’d squealed from new until their last use when they’d been worn down to about 1mm) with another pair of Shimano resin pads (without fins this time) and the squealing vanished; to date it’s failed to return.

I’ve no idea why the first set squealed but a pad change may be enough (although if you’re sure you’ve got oil on the rotors you’ll need to get this off first).

Clean the rotor

This.

replace the pads

This.

chuck some muddy water on the brakes and ride them down a big hill a few times

This.