Chronic brake squeal in Yeti SB6c

[open roader]

I built up a Yeti SB6c 3+ years ago using Shimano XT M8000 brakes.

Since day 1 it has braked very nicely at speeds above 10-15km/hr but exhibits a horrid high pitch squeal when I slowly come to a stop ie) at walking pace to stationary.

I've tried a few pad materials / rotor brands and combos, the current metal pads have had over 5km of actual braking done as emergency type braking as a bedding in process (I live just around the corner from a long steep downhill)

I've tried sanding / cleaning the pads. I've been advised not to clean the built up pad material off the rotors. The rotors are dead straight, the calipers are aligned to the rotor perfectly..................

No matter how well I bed in my brakes, both back and front squeal when coming to a stop.

I've run out of logical brake stuff to eliminate bar buying a new set of calipers.

Is my frame to blame - worn bearings in the suspension linkages - anyone heard of this causing brake squeal before. This is my first carbon frame MTB - maybe it's the carbon frame - I don't know - going mad.....slowly.........

[chasea]

If your pads got contaminated during the sanding/ cleaning phase then you're just bedding that stuff into the rotors. You can clean rotors with soapy water and/or rubbing alcohol and a clean rag. I'd suggest cleaning rotors and a fresh set of pads. Recently cleaned rotors might howl on a test ride but they get quiet quick on a real ride.

Or just go for fresh pads and rotors together.

[Peter Polack]

I think it might be the finish on the rotors. An extremely smooth, non-porous, anodized surface would be like a wet finger on a glass rim.

I'd try scuffing up the rotor surfaces. Try a scotchbrite pad first. If that doesn't work, try 400 grit sandpaper.

[thollandpe]

Why not clean the built-up pad material off the rotors? Why not use something coarser than 400 grit?

It’s pretty normal to get the rotors wet and deal with sand or dirt that will do the same thing. I’ve sometimes carried a water bottle to squirt it on the brakes during the bedding in process. The only thing I’ve been unable to quiet are BB-7’s. Honk, honk, howl howl. I have XT M8000’s too but my only complaint, besides the often-discussed variable bite point, is that the front brake looses oomph over time. Same lever feel, no noise, just loss of power.

As Chase says, dealing with contaminated pads is tough, you aren’t going to clean them. Could you have another cleaning or maintenance process that fouls the pads? An essential oils vaporizer in the bike garage? Eucalyptus and aloe frame polish?

[jimcav]

are rotors slightly warped? that is another thig that has caused squeal for me, although the surface contamination is more likely culprit

[open roader]

Thanks to all who replied.

I tried some 400 grit on the rotors - made it considerably worse in that it now howls at a higher speed right down to walking pace.......................

So I tried some 240 grit - a couple of dozen rotations of the rotors each side but alas same deal.

I then proceeded to do what I've been expressly told not to do and cleaned the rotors with acetone on a clean rag...... still same deal.

I just want to get a couple of things clear. I've tried out 2 x pairs of metal pads and 2 x pairs of resin pads.

I'm familiar with cleaning the pads off on a flat block with emery paper and washing them afterward.

I've even tried commericial brake cleaning fluid on the pads, caliper pots and rotors to no effect

I've tried a pair of Avid, a pair of Shimano Ice and a pair of regular Shimano rotors, all the same size as each other and all brand new - running dead straight. No difference at all between the three sets.

It's cost me a couple of hundred bucks trying to sort this and here's the thing. 18 months back I built up a Giant Trance frame with the exact same M8000 brake set. It's running resin pads on regular Shimano rotors and is 100% silent right from the start. I've pulled it apart side by side with the Yeti and put it back together in sequence just in case I missed a spring location or a lock bolt etc. None of it has made the slightest bit of difference.

I've been doing my own bike building / servicing since 2007 over maybe 8 or 9 bikes now. I'm a fairly calm, methodical operator but for the first time after 3 years I'm completely flummoxed hence me wondering if I should be looking at something awry with the frame?

I'm loathe to sent the bike to my LBS mechanic simply to maintain my 100% record of sorting my own stuff.

Uber frustrating..................

[Peter Polack]

Maybe the calipers on the bike are faulty. Try swapping just one of the calipers from the Giant onto the problem bike and see if the problem appears.

[Lionel]

Thanks to all who replied.

I tried some 400 grit on the rotors - made it considerably worse in that it now howls at a higher speed right down to walking pace.......................

So I tried some 240 grit - a couple of dozen rotations of the rotors each side but alas same deal.

I then proceeded to do what I've been expressly told not to do and cleaned the rotors with acetone on a clean rag...... still same deal.

I just want to get a couple of things clear. I've tried out 2 x pairs of metal pads and 2 x pairs of resin pads.

I'm familiar with cleaning the pads off on a flat block with emery paper and washing them afterward.

I've even tried commericial brake cleaning fluid on the pads, caliper pots and rotors to no effect

I've tried a pair of Avid, a pair of Shimano Ice and a pair of regular Shimano rotors, all the same size as each other and all brand new - running dead straight. No difference at all between the three sets.

It's cost me a couple of hundred bucks trying to sort this and here's the thing. 18 months back I built up a Giant Trance frame with the exact same M8000 brake set. It's running resin pads on regular Shimano rotors and is 100% silent right from the start. I've pulled it apart side by side with the Yeti and put it back together in sequence just in case I missed a spring location or a lock bolt etc. None of it has made the slightest bit of difference.

I've been doing my own bike building / servicing since 2007 over maybe 8 or 9 bikes now. I'm a fairly calm, methodical operator but for the first time after 3 years I'm completely flummoxed hence me wondering if I should be looking at something awry with the frame?

I'm loathe to sent the bike to my LBS mechanic simply to maintain my 100% record of sorting my own stuff.

Uber frustrating..................

I would trash these brakes and put some magura in there.

[sk_tle]

Are your hydro hose well secured and immune to vibration ? This can sometimes be the culprit. I would tape or zip tie the hose as close as possible to the caliper before ditching them. Watch this video :

[jimcav]

can you swap a caliper from another bike.

only other thought i have is the pad to rotor alignment. I bought a Hayes disc brake gauge alignment tool and it eliminated squeal on my bike, I got mine at amazon as i wanted it asap for a trip, but it is this:

https://www.jensonusa.com/Hayes-Brak...hoC-pAQAvD_BwE

[suspectdevice]

Have you checked your swingarm for cracks?

[open roader]

Have you checked your swingarm for cracks?

Yes. Both this past weekend in the bright daylight I removed the wheels, flipped the bike upside down (and put on a pair of reading glasses) there is nothing visible in the paintwork over the whole frame and I did check it with the tap test when I had the swing arm off and applied the replacement frame skin about 12 months ago. The linkages also seem fine, no play, all torqued down firmly etc. The bike has covered bugger all miles and all of it either gravel roads or moderate trails, as far as the seat of the pants feel goes I'm yet to even get any air over bumps - all sedate riding so far.

I'm yet to swap out a caliper as my Trance is being ridden by a friend at present.

I think it's time to look for someone locally with hydro brake experience and clearly more knowledge than me as I've been over the basics a dozen times and I really don't want to spend more $$$ on rotors/pads/calipers nor do i want to spend any more time chasing my tail until I know what the cause is.

So for now I'm calling it a defeat...................

[sk_tle]

For what it's worth, I saw a video of Nino Schurter descending a flow trail with his XC bike and it was squealing at every braking point. If the world's best mechanic can't do anything for the world's best XC racer, maybe we should just accept defeat ?

Additionnally I have a gravel bike that uses Sram brakes, but shimano rotors and which exhhibit similar symptoms. Squealing at low speed, totally silent when I have to break hard. With a different set of wheels with Sram centerline rotors it is silent. My wild guess was that the shimano rotor ̶s̶u̶c̶k̶s̶ material squeal when cold. I didn't try to address it and view it mostly as a feature as most of my low speed / cold braking are done in urban area and makes the pedestrians aware of me while it is totally silent when descending a long downhill in the countryside.

[dually]

I’ve had this issue a few times on various shimano model brakes. My fix was to remove the pads - bake pads at 450deg for 20min - clean with alcohol - install and proceed with bedding.

This process would have to happen if the bike sat for a while. I don’t know if they pads react to humidity or absorb other contaminants, but it seemed (and worked) to heat them up.

[Drew]

Try a 0.5mm or 1mm spacer under the caliper (move it up a tad). This has worked wonders for me in the past with Shimano squealers. I’ve also saved brake pads that I thought were contaminated by heating them up with a torch... but that’s a bit of a guessing game. Went too far with one and melted the icetech fins. The black anodize on the icetech fins will turn brown, but you can evaporate the contamination from the pad this way. Takes a deft touch but I have had success with that too. 450f in an oven seems like a much better plan... unless your SO threatens divorce if bike parts are placed in the household oven, as mine did.

FWIW, I have since pretty much abandoned Shimano brakes. As much as I like the feel of them, the new SRAM stuff is really good.

[open roader]

Try a 0.5mm or 1mm spacer under the caliper (move it up a tad). This has worked wonders for me in the past with Shimano squealers.

Whooo Hooo! We have a fix - partially..................!

I found some correct sized 0.5mm toothed washers - the front brake is fixed instantly.

The rear is still squealing at lower speeds but not as bad as previously.

I ran out of time to play about more this afternoon but I may try a 1mm thickness washer to lift the rear caliper up.

Many thanks for the tip - priceless and something I had not considered before - always thinking about lateral caliper alignment............

[open roader]

Ok, next day follow up and it's all magic!

I removed the 0.5mm tooth washer and added a 1mm flat washer under the rear caliper and it runs perfectly silent - instantly!

A simple yet so left field remedy. The 20 cent washers complete the $6,000+ bike............

I'm so pleased to finally have this bike running the way I intended after 3.5 years of frustration. I'm not going to even think any further as to why raising the calipers off the mounting lugs is a fix - just enjoy the ride..........

[Drew]

Ok, next day follow up and it's all magic!

I removed the 0.5mm tooth washer and added a 1mm flat washer under the rear caliper and it runs perfectly silent - instantly!

A simple yet so left field remedy.

Good to hear! (or not hear, I guess....)

Enjoy!

[72gmc]

I enjoy quirky remedies like this.

[darkmother]

Interesting fix. I'll keep this in mind the next time my Shimano road discs are giving me grief.

Question for all: Let's say I have a leaky caliper, and it fouls the pads and rotor with oil.

Can I salvage the rotor? Can I salvage the pads?

I assumed that the rotor could be cleaned and re-used, but recent experience suggests otherwise. My cleaning was with alcohol first, and then brake cleaner second, wiping with a clean shop towel afterwards.

Should I sand the rotor?

The collective insight here has been most helpful, I welcome any advice that you may have.