Squeaky rear disc brake

bonk_king

Forgive me in advance if this has been done to death already.

I have a new Vitus Nucleus MTB. I've done about 100kms of just pootling about thus far. A few basic off road treks, nothing too dirty or punishing. The brakes have been fine, effective and quiet.....until my last ride, when they started squeaking. Just a few seconds at a time, then silence. Then again, just random, no pattern to it at all.

I took the mechanism apart yesterday, give it all a bit of a wipe, though it was clean anyway. I put it all back together and went out last night for a few miles but the squeaking continued.

I took the mechanism apart again today. I eased the hydraulic barrel mechanism as far back as it would go, as to give me the biggest gap possible for pad clearance, and put the mechanism back together. I spun the back wheel for a few minutes and it was silent, no pad/disc contact at all, how it should be.

Then I gently applied the back brake. And the rubbing started again.

To me, it seems like the "springiness" of the release mechanism plate isn't good enough to open the pads back up and push the barrel mechanism back into place, which would ensure pad clearance everytime the brake lever is released.

Surely I don't need a new "release plate" (I'm not sure what it's proper name is, in the picture it is top left), as the bike is new. Is there a hack to help release the pads from the discs to ensure proper clearance and hence no squeaking?

oxoman

I'm assuming there hydraulic brakes and it's possible that it needs bleeding. Given its a new bike it's highly likely. I'm assuming you've re-centred the wheel to the caliper. If not try that as a starting point.
https://youtu.be/uk_nC9anQcM
They also do bleeding tutorials and mech disc brake tutorials. YouTube is your friend.

reaperactual

I've got my Buddy's Nucleus at the moment, took it up and down the street as he heard the same noise. It just needed the rear caliper aligning properly and it stopped squeaking.

This one has the Clarks brakes which don't have much clearance between the pads and rotor.

The pad spring only keeps the pads in contact with the pistons, they don't apply the pushing force. It's the piston seals that deflect back into position which recesses the pistons when you let go of the lever.

mully79

The metal spring is merely an anti rattle spring. It does not push the pistons back.

There is a hydraulic effect in conjunction with a square profile piston seal that deforms when the piston presses on the pads.

This movement isn't huge so as above post ,brake caliper needs to be central and straight and any air in the brake line reduces any hydraulic effect so may need bleeding.

Note if the calliper wasn't straight and/or the pads have worn slanted one of the pistons may stick in the calliper and cause problems.

bonk_king

Thanks guys, I misunderstood how the mechanism works. I thought the springy clip thing was integral to keeping the pads clear of the disc, apparently not!

I understand it a little more now and will perform a few further aligning tweaks as per your guidance.

Thanks.