oh oh...new noise in older XTR system
I have XRT brakes on my 4 1/2 year old Mojo SL and I am very happy with them. At my light weight, they are a one finger brake with great modulation. The rear system has a very slow fluid leak due to a crash or two...or three...affecting the reservoir seal, and every few months I add a little fluid to the system without a full bleed. Recently the rear caliper area makes a harsh squeak noise when I pull the lever at the handlebar. The pads still make good contact and the pistons retract properly, but SOMETHING down there is making this strange noise. I've cleaned things up without solving the problem. Any ideas ???
Probably oily pads, are affecting the bed-in of the rotors...
Cook the pads on medium heat in an old fry pan, the lightly sand off the carbon and reinstall, after a good soapy wash of the brake area.
Or just get new pads.
Drinkin' the RIP9 Koolaid
Wouldn't hurt to lightly sand and clean the rear rotor too. Then rebed the new pads properly to make sure that the adhesion layer on the rotor itself isn't contaminated.
My guess is the seals on the caliper end are starting to leak a bit, it's been known to happen with some of the older XTR brakes. The seals around the piston will seep oil onto the back side of the pads and it eventually gets all the way through at which point the brakes start squeaking. Let it go a bit longer and it becomes a deafening honk. Unfortunately there's not much you can do other than replacing the brakes.
To confirm that this is the problem, give everything a good cleaning then ride the bike for a few days. Right after you finish riding, remove the brake pads and check the back side for oil residue, if you see any oil, the seals are toast and you'll need new brakes.