[92gli]

Need ideas. I'm completely stumped and pissed at my rear brake squeal. I've never had this problem with shimano brakes except when a caliper leaked. Braking power is fine, so I'm sure its not a leak. But I've checked for that 3 times now.
Brakes are xt 785 lever/xt 8000 caliper with shimano xt rotors . caliper is about a year old. All pads are metallic.

This all started with a simple pad change. A while back I purchased 2 sets of ice tech pads from a local guy and stashed them away. I installed one of the new sets about a month ago and on the 2nd ride with them I started getting a crazy squeal on long-ish descents. Checked the pads for oil, looked fine. Put a bleed block in the caliper and squeezed the lever about 40 times to see if any fluid was leaking. all good. I thought maybe I got some dud pads, so I swapped in the 2nd set from the guy and bedded them in on a hill near my house.

Next ride, same problem. It was driving me so crazy I swapped my front and rear rotors trailside. That didn't help.
Got home and noticed some play in my rear wheel. Took the hub apart and found that the main bearings had some lateral play, which wasn't surprising given the hub is at least 4 years old. Maybe there was some vibration at the hub that was causing the brake noise? Ordered new bearings, got everything back together and thought I had it licked. Next ride, same issue.

This week I bought a new galfer rotor and another set of metallic shimano pads. Just got done my ride and it's still doing it. I have a set of organic pads somewhere, and I'll try them out. But I know I won't like how they function, so thats not a long term option. (by the way, the galfer rotor isn't even close to round - crap quality!)
ANY IDEAS???

 

[92gli]

BTW - Frame is a santa cruz 5010, so there aren't any chainstay pivots in the mix.

 

[mrpizza]

I had a set of pads in an slx rear caliper that squealed and squealed. I ended up burning them off with a torch and sanding them down.

Still squealed after that so I said screw it. However I noticed on my morning ride today I no longer have squealing brakes. I dunno. Resin pads.

 

[slimat99]

Try this: remove pads, get them as dirty as you can by sticking them in the ground, then rub the pads aggressively against each other until all the dirt is scrubbed off. Repeat this two or three times. Don't use any cleaners. Instal pads and see if that shuts them up. This seems to work for me better than sanding and cleaning. Not really sure why because it's basically just a course sanding without cleaning, but it's worked pretty well for me. I've even shut up pads mid ride going from painful squealing back to normal just with dirt.

 

[mtnbkrmike]

Metallic/sintered pads are going to be louder (obviously) than organic/resin pads, but whatever. I live with the occasional noises from mine (same XTs as you and Guide Ultimates).

I have a bottle of IPA that I keep in my truck. As part of my pre-ride lube ritual (every now and then - not every ride), I wipe the rotors down. Simple, quick, unrefined, and probably pretty lame for some, but it seems to work just fine for me.

My brakes were squawking pretty loudly last evening. I can usually get rid of it mid-ride by applying different pressures on long descents. I got rid of all the racket within a few minutes last night, and usually can, just by fiddling around with the lever pressure mid-ride. I am fortunate to have loooooooong downs on most rides so sustained braking is the norm.

I have a really bad noise issue. I seem to be affected by bike noises much more than everyone else. 2021 goes down as my biggest biking year in my life, but also the worst mechanically, including various noises with almost every bike, that slowly drive me into a state of madness. With a little (okay, a lot) of help from the top mechanic at my LBS, I finally got things sorted. For now at least.

Good luck. Please let us know what worked for you.

 

[Smokee300]

I still would not rule out a caliper leak. I recently went the something similar with 4 Pot SLX's. The braking power was fine, but the brake still howled despite cleaning, changing, replacing pads and, sanding. Keep an eye on the back of the pads, you might be able to see a ring of oil or blot the back of the pad with tissue paper.

 

[KVV]

After numerous experimentation in similar situations, I just bake the metal brake pads in the over at 400 degrees Fahrenheit for 30 minutes. So far it helped in about 3 situations out of 4. Torching or burning over the gas stove never worked for me. The last time I ended up replacing the rotor, which I seemed to glaze pretty badly. The oven exercise is free. I always do it first.

 

[blkdout]

Whenever mine have started making noise, the first thing I do is spray a rag with Carb and Choke Cleaner, pinch it on the rotor and spin the wheel a few times. Works 95% of the time. Not Brake Clean or degreaser or alcohol... Straight up Carb Cleaner. It's basically just acetone in aerosol form. The 5% it doesn't work, I sand the pads. Usually never an issue thereafter. I'm also ultra careful not to touch the pads or rotor surfaces, make sure the brakes are protected from anything being sprayed on or around the bike and very careful with chain oil too.

I am interested to see what works though being you tried a new rotor and pads.

 

[DoctorJD]

I still would not rule out a caliper leak. I recently went the something similar with 4 Pot SLX's. The braking power was fine, but the brake still howled despite cleaning, changing, replacing pads and, sanding. Keep an eye on the back of the pads, you might be able to see a ring of oil or blot the back of the pad with tissue paper.

This. It seems like there's one common denominator in the OPs story: The caliper. Over the last couple of years, I've heard story after story of leaking Shimano brake calipers. Hell, I had one myself. OP, do as Smokee said: Do the blotter test on the backside of the pads. This is the way I discovered my leak, as well.

 

[EatsDirt]

Haven't read above but I'll give my .01 having too much of experience with this...

Beyond the whole caliper leaking/glazed pad thing... it seems that caliper alignment and pistons extended at uneven rate can affect this.

I clean, lube (mineral oil) and carefully exercise pistons then re clean. Make sure they're extending a similar rate/distance with pads installed and caliper loose. Tighten caliper down as centered as possible checking for rotor deflection through rotation. Check pistons again.

I sand pads with 150g dry until the copper color comes back, then wet sand with high percentage rubbing alcohol.

This has worked for me. YMMV

 

[CrozCountry]

Noise sometimes is only solved with Organic pads, or a different brand of pads.

To try to salvage your current situation, I would clean the discs with alcohol, light sand of the pads, and real break in on the street or on a flat trail. The key to break in is low temperature. You want the brakes to get back to their original power without heating them up to normal riding temp as you would get on a downhill. As they start braking harder you can increase the temp.

As far as oil leaks, after a few rides, take the pads out and look at the back of the pads. If there is an oil leak, you will see some oil residue on the back of the pad, usually in a shape of a piston (a circle). It can also happen after you leave the bike for a couple of weeks standing. Its very hard to replicate in the workshop. If you would get a leak at the workshop the rate of leak will be extremely high.

 

[Stevebiker]

I've had issues with mine. Mostly after sitting all winter and this spring was really bad. Tried all the usual fixes and even had my LBS on it without success. On the leaky caliper, it doesn't take much at all. A good way to tell if that's an issue is pull the pads off, clean the piston area and put a block between the pistons. Use a strong rubber band to squeeze the lever and leave it sit a while, then check closely. One mechanic I know will put a paper receipt on each side of the block afterwards and squeeze the lever. he says a receipt will show wetness really well and if he sees any residue at all it's leaking. Anyway, mine weren't leaking so that wasn't it.

He also said on problem brakes, he never changes the pads without changing the rotors at the same time. Which is what I ended up doing and it worked. A couple of things to note however. He mentioned getting the pads/rotor good and hot when breaking them in so I did a better job of that. On a long downhill, getting up to speed and getting on them medium hard, then accelerating again and quickly getting on them again before they had a chance to cool down. I repeated this a few times. Also, they didn't have any ice rotors so I used a different brand. So it could have been the way I broke them in, the different brand rotor, or changing the pads and the rotor at the same time. Either way, I spent 3 weeks out west with the quietest brakes I've had in quite a while.

 

[OldMike]

My 2021 SJ rear brake howled from new. Tried EVERYTHING to no avail. I even swapped the pads from the Front brakes (both SLX) and the rear still howled and the
rear pads were fine up front. This lead me to believe maybe the rear caliper was mis-aligned however try as I might, I couldn't fix it.

In the end I opted for Resin Pad and found I like them better (for the back) as they're less likely to lock up.

 

[mtnbkrmike]

My 2021 SJ rear brake howled from new. Tried EVERYTHING to no avail. I even swapped the pads from the Front brakes (both SLX) and the rear still howled and the
rear pads were fine up front. This lead me to believe maybe the rear caliper was mis-aligned however try as I might, I couldn't fix it.

In the end I opted for Resin Pad and found I like them better (for the back) as they're less likely to lock up.

Question - did you change your rear rotor or at least clean/sand it before the switch from metallic to organic? If not, have you found that your resin pads have been disintegrating at an alarming pace?

 

[OldMike]

Question - did you change your rear rotor or at least clean/sand it before the switch from metallic to organic? If not, have you found that your resin pads have been disintegrating at an alarming pace?

I cleaned it with automotive brake cleaner and also lightly sanded it as it looked a little glazed. Still didn't work. Once I discovered the pads weren't the culprit I felt there was no need to bother with rotor swapping although that would have determined if it were in fact the rotor or the caliper.
I just wanted to ride so the Resin Pads were critical IMO in getting me back out there (noise free).
Then I discovered I liked the Resin for the rear brake (not the front as I want instant power there).

I have about 100hrs total on the front pads and 75hrs on the rear/resin.
Haven't noticed any more wear than normal on the Resin. Matter of fact, I'd say they have 20% more then the front which is surprising as I use them almost exclusively.

NOTE: The Resin pads were far thicker than the OEM as I had to adjust the lever throw as they were out too far once I replaced the rear OEM pads with the resin..

 

[TylerVernon]

Mine have squeaked this year because of the tall grass. Plants have oils and they're impossible to avoid.

 

[Smiles for miles]

Ice tech rotors have always given me trouble. I switched to SLX rotors and all is well. Seems like ice tech warps or something.

 

[funks]

If you want no noise, trash the shimano sintered pads.

Get MTX pads (gold or red) and you'll be good to go.

 

[blkdout]

I use Ice rotors and Shimano metallic pads. Whisper quiet.

I promise Brake Clean and Alcohol isn’t strong enough to clean sh!t. Unless you’re taking the time to rinse and repeat, those weak ass chemicals just smear around the contaminants. Acetone is the way to go.

 

[Jayem]

Just recently had a Hope brake (rear) howling like crazy on the new FS fat bike I built up. A resin pad swap shut it up. I've never had problems with my XTRs on my other fat-bike, but they use resin pads front and rear. If I got the sintered pad up to heat or drug it for a while, I could make it shut up, but as soon as it cooled back down or got a little moisture in there, it was howling. Luckily I don't need sintered-pad-power on the snow, but I definitely do on the dirt. The resin pads on my other hope brakes, V4s, are completely insufficient. They come with 3 sets of pads and I thought I'd use up the resin ones first, but they are so bad that I can't use them...