Squealing disc brake

[sjbraun]

So, my front disc brake just started squealing, but only just before a full stop. It's quiet as I decrease speed, but at that last little bit before I come to a complete stop it screams like a banshee. I've cleaned the rotor, but that made no improvement. Any thoughts?\
The brake is a GRX and the disc is a Shimano RT-800.

Thx

[fa63]

Your pads are probably contaminated. Try sanding them and see if it works (it doesn't always work, especially with resin pads). If not, new pads will likely cure your problem.

[eddief]

Using a bit of alcohol under controlled conditions. Then I sand the soot and contamination off. Then clean one more time with alcohol. Dry em and try em. Often it works. Sometimes not. While the pads are out I also use a qtip dipped in alcohol to clean the surface of the pistons. Don't forget to reclean the rotor.

[prototoast]

Originally Posted by fa63

Your pads are probably contaminated. Try sanding them and see if it works (it doesn't always work, especially with resin pads). If not, new pads will likely cure your problem.

In addition to this, I've also had similar issues from a warped rotor, and a rotor that wasn't evenly spaced between the pads.

[Slow]

What did you clean the rotor with?
I usually just clean my rotors and pads with alcohol wipes after each ride.

[eddief]

and then with a clean rag and alcohol.

[thwart]

Originally Posted by Slow

What did you clean the rotor with?
I usually just clean my rotors and pads with alcohol wipes after each ride.

Wow.

If I even consider buying a road disc bike for my use (no mountains or riding in rain to speak of), someone please smack me upside the head.

[oldpotatoe]

Originally Posted by thwart

wow.

If i even consider buying a road disc bike for my use (no mountains or riding in rain to speak of), someone please smack me upside the head.

potd...

[fourflys]

Originally Posted by thwart

Wow.

If I even consider buying a road disc bike for my use (no mountains or riding in rain to speak of), someone please smack me upside the head.

I had a similar thought.. the only thing that keeps me looking that direction is the ability to run larger tires on a nice frame.

[tuscanyswe]

Someone will shortly tell you that disc brakes dont squeal and they are less noisy than caliper brakes. If they in some remarkable way do make a slight noise its likely cause you did something wrong. Like not breaking them in properly for 5 hours before using them or similar. The procedure to fix these brakes are also much simpler than to fix caliper brakes. Its a mere 5 hour procedure of straightening the rotor preferably also put in in the oven or frying pan of choice then let it sit before you rub it in with alcohol (a special kind of sort, no not bourbon) then its ready to go again once you have changed your week old pads to new ones and also removed any airbubbles in your system just like you just did the other week.

Now this is a user error problem and not a disc brake issue per say so if this does not help the likely cause is that your frame is out of alignment or the fork so double check that and you should be good to go after a light sanding of the brake mounts. (at least until the next shower).

[fa63]

I would say that is excessive and might do more harm than good, but if it works for you, then so be it.

On the gravel bike that I just sold after almost 4 years I never had to do any "maintenance" on the brakes (Shimano) except replacing the pads (and clean the pistons while the pads are out). The SRAM brakes on my new bike on the other hand seem more finicky already (less clearance from the pad to the rotor so I struggled getting it perfectly centered) but let's see how it goes in the long run...

Originally Posted by Slow

What did you clean the rotor with?
I usually just clean my rotors and pads with alcohol wipes after each ride.

[nmrt]

Alcohol wipes after each ride? Pffft....
I clean my rotors with EVOO. Only the best!

Originally Posted by Slow

What did you clean the rotor with?
I usually just clean my rotors and pads with alcohol wipes after each ride.

[John H.]

Is your setup new, used, how many miles?
What do you use to wash your bike?
I use dawn dish soap and warm water. If I don't do a good job making sure that I get it all off the rotors, it may squeak.
Here are my tips.
1.) Make sure adjustment is good. Rotors centered in brake, pistons moving evenly. Check pads. Sand if needed. Same for rotors. Sometimes a sanding helps.
2.) Cleaning- To make sure- alcohol can help. I have had even better luck with Motorex brake clean. Can get on Amazon. A SRAM mechanic at an event turned me on to this. Use a clean microfiber cloth and wipe with some force.
3.) Braking technique. I find that I am most likely to squeal with a really hard pull of both brakes. I try to alternate and also let off. Also use the least amount of force needed, vs. grabbing hard to stop every time.

[rollinslow]

this is an RT-800 rotor? Just confirming because they are likely warping from heat. This is such an issue with those that Shimano discontinued them and remade the ones announced a few days ago.

The noise happening right before you are completely stopped is the tipoff. If contaminated it would likely cause noise sooner. I would get rid of the rotors personally and switch to XTR.

[windsurfer]

My current ride is it 40k+ miles without sqeals or wiping the braking surface with alcohol. Not only that, but my disks are much bigger and dissipate heat much better

Rim brakes for the win.