[Schmucker]

I have Shimano R785 brakes. The new DI2 hydros. At low speed, just before stopping, they squeel really bad. All other times they're fine.

Things I've done:
Cleaned everything with alcohol and also tried brake cleaner.
Sanded pads
Torched pads
Sanded rotors
Anti-squeel to back of pads
Sanded rotors
New pads
New rotors of same type (XT RT86 160mm 6-bolt)
Avid Cleansweep G2 rotors

I am losing my mind with this.

Any other suggestions of things to try?

 

[11053]

Is the caliper perfectly centered over the rotor?
Do the caliper pistons engage the rotor at exactly same time?

 

[Schmucker]

I've also tried different wheels. This is on both the front and rear brakes.

Calipers are aligned and pistons are engaging equally.

 

[giantdefy]

I did everything you did, but the only thing that worked was putting a piece of electrical tape to the back of both pads. Super quiet now.

 

[Schmucker]

Electrical tape did not do it.

 

[Hawgzilla]

All disc brakes squeal at one time or another. Just ignore it as long as they stop you when you ask them to.

 

[COLINx86]

By low speeds, do you mean like >2mph? I've noticed on 5 different bikes now, that some Shimano brakes just squeal at very low speeds, the second you actually start riding the bike the squeal goes away, though.

 

[Schmucker]

Well, I'd say single digit speeds. And it isn't just a light squeal, it's everyone within the block looks at you squeal.

But I think I fixed it. Electrical tape + different rotors. Rode to work (only two stops though) and no noise.

 

[Schmucker]

And not fixed completely. Light stops at very low speed are fine. Heavier brake input at very low speeds causes the squeal, much like the scenario COLINx86 described. I'm going to assume that's as good as I can get. I'll try a few different brands of rotors and see if anything works better.


EDIT

I tried some old Hayes Mudcutter rotors and they are silent now.