Brake disc vibration

steelo

I was doing some heavy braking last night and I was getting some very loud, very violent vibration from the rear brake as I was slowing down. There was no noise or vibration when I was only putting slight pressure on the brake but under heavy braking the noise and vibration was almost unbearable. It's not happened before and I have no idea why it's happening now.

Brakes - Avid Juicy 5 caliper & lever, 160mm avid rotor, relatively new sintered pads, probably about 20 hours on the bike.

Someone suggested putting some grease between the pads and piston pins.

cooldad

Don't put grease anywhere near your brakes.
Check to see if anything's loose.

steelo

That was my immediate reaction, I responded with "you what? grease the brakes?" to which the reply was "behind the pads, not on the pads, mine used to make a hell of a noise but with grease behind the pads they are silent". I think his idea is that the vibration is due to the pad on one side being slightly loose. My idea is that it is more likely to either be the caliper or the disc isn't done up tight enough.

Would I need new rotor bolts if I've taken the rotor off numerous times so that most of the blue thread-lock is now non-existent on the bolts?

cooldad

It's done on cars, as anti squeal, which have monster brakes and can burn off a bit of crud.
Bikes don't.