Brake noise/moaning


Nov 23, 2010
San Diego
I used to have a 180mm shimano XT rear rotor and I just went up to a 203mm shimano XT rear rotor. Brake caliper is Shimano SLX.

The 180mm was nice and quiet. The 203mm moans when braking. It sounds like rotors sound when they get wet. The wheel spins freely when not braking, there' no rubbing, the caliper looks aligned, the brake pads are fairly new.

Any suggestions?


Oct 28, 2008
Clean the rotors with rubbing alcohol and maybe try lightly sanding the face of the pads.

It could also be that the pads just need some time to adjust to the new rotors. They might not be exactly parallel to the rotor right now, but after some use they should be.


Apr 21, 2005
Raleigh, NC
^^exactly. If the 203 rotor is brand new, then you'll have to brake it in. After the sandpaper/rubbing alcohol, find a big hill and make a few trips down it with the brakes on.


Turbo Fluffer
Aug 8, 2005
My own world inside my head
Sooooooo....... Check this..... Its all about surface RA... that translates to how rough the surface is.

Glazing is something that happens, its normal.... as to how much... thats another story. Issue here is the Surface RA on the rotor is nice and hi, yet the pad is nice and low.

makes for a wonderfull noise. Fun aprt now is when you put the other rotor back on, its gonna make noise now too since the new rotor is starting to Deglaze the old pads ETc Etc.

What you need to do is..... Hone the two together.

Stay with me here guys........ Really fast way to "burn" the pads and rotors together, and make them last longer..... No this isnt bull****..... no this isnt a joke..........

Take a paper towel, put some wd40 on it, and lightly wipe down the rotors surface. Then ride a moderate hill, steady grade....... ride the brakes a bit untill you burn off the wd40........... WD40 is a great honing agent, eliminates noise, gives you the longest pad life, best stopping power.

Dont knock it till you try it