Squealing BB7 Disc brakes

[ianrauk]

OK, knowledgeable CC folk.
The new bike has Avid BB7 disc brakes.
Did it's first commute tonight.
On the way back it was raining and boy did the brakes squeal. Embarrassingly loud.

So, is it a case of waitng for them to bed in?
Is it normal for wet weather?
Or is there something I can do to alleviate it? (WD40 on the rotors?*)

Thanks for your help.

*joke

 

[gaz]

*jealous* I couldn't brake this evening *Stupid rim brakes*

It's a new safety feature, an inbuilt brakezound.

 

[potsy]

I was using it on my bb5's as a brakezound (nice one gaz) whilst on the shared path/tpt.
Mine was still doing it when it went in for it's checkover, the lbs said they had just cleaned the pads/rotor up, seemed to fix it for a while.
Was squealing a bit yesterday in the wet again though not as bad.

 

[HovR]

Try cleaning the pads and rotors of all dirt/oil. Mine squeal at the start of wet rides after the bike has been sitting outside in the bike racks, but this normally clears up after a few brakes.

 

[ianrauk]

Try cleaning the pads and rotors of all dirt/oil. Mine squeal at the start of wet rides after the bike has been sitting outside in the bike racks, but this normally clears up after a few brakes.

They are brand new pads and rotors as it's a brand new bike so there was no dirt/oil to clean off.

 

[HovR]

Odd. A friend of mine's bike with discs squeals extremely loudly in the wet, whereas my notably cheaper discs hardly squeal at all after the disc has been cleared - The main difference being mine have more miles on them, so maybe that is it?

Some people recommend using organic compound pads to reduce squealing, and others recommend filing the top surface off the pads. Never tried these myself, but maybe it'll help.

 

[Jmenorton]

My bb7 do the same, even worse in snow, intresting when riding through a busy town centre. Again new bike and brakes. Might give organic pads a go when i wear out the current ones, got some alcohol wipes aswell, to clean the rotors next time the bike gets a clean.

 

[MacB]

Is it both brakes Ian?

Mine haven't been an issue can you tell how they are set up positionally? What I mean is have a look at where the rotor passes through the caliper, is it central or over to one side?

On mine, following those setup directions you've seen, my rotor sits closer to the inboard pad, this minimises the amount of disc deflection when braking. The outer pad pushes the rotor onto the inner pad which doesn't move. I have read, but don't know if it's true, that the further the rotor needs to be pushed the more likely it is to squeal.

 

[RedRider]

I replaced the pads on my Shimano slx disc set up and the knowledgable sounding bloke in the shop gave me a few tips for bedding them in. He said try not to feather the brakes for the first 50 miles because this can put a sheen on the rotors which impairs stopping ability and causes squeals. Instead he said brake hard (so's you almost stand on the front wheel when using the front brake and so the back wheel locks when using the back brake). He suggested finding hills and braking hard on descents.

I'm just passing on what i was told and claim no expertise but I can confirm my brakes now work well without screeching.

 

[GrumpyGregry]

All disc brakes squeal but most of the time humans can't hear it.

Yours aren't bedded in yet, and once they are you get used to the squealing which comes and goes especially if the discs get dirty.

one american bb7 mtn user claimed he cured the squeal permanently by sticking a car wheel balance weight on one of the rotors legs. Guess the mass change shifts the resonant frequency out of the audible range.

 

[ianrauk]

Is it both brakes Ian?

Mine haven't been an issue can you tell how they are set up positionally? What I mean is have a look at where the rotor passes through the caliper, is it central or over to one side?

On mine, following those setup directions you've seen, my rotor sits closer to the inboard pad, this minimises the amount of disc deflection when braking. The outer pad pushes the rotor onto the inner pad which doesn't move. I have read, but don't know if it's true, that the further the rotor needs to be pushed the more likely it is to squeal.

Yes it's both brakes Al.
I did read about having the inboard pad close then the outboard.
I will have a look at that set up link again and check at teh weekend when I have time (also time to dig out that BB for you)

 

[ianrauk]

Thanks for the suggestions everyone. All advice taken on board.
Will check at the weekend to make sure the distance of the pads to rotor is correct.
If it continues then I will look at different pads.

 

[MacB]

Yes it's both brakes Al.
I did read about having the inboard pad close then the outboard.
I will have a look at that set up link again and check at teh weekend when I have time (also time to dig out that BB for you)

No rush mate and also scratch some of that advice it was nonsense thinking about it. The rotor position doesn't dictate the pad to rotor distance, setting the pads themselves does. Still worth a try mind, but Gregs right as well on the bedding in and the resonance bit. Though I have no idea if a weight would work to change the resonance in that way.

I've had a few squeals early in the odd ride but they soon vanish once the brakes are used a bit.

 

[Andrew_P]

What sort of pads? Ihave read Organic are better than sintered but wear quicker

 

[ianrauk]

What sort of pads? Ihave read Organic are better than sintered but wear quicker

I have no idea Loco. Came with the bike so I can imagine they are whatever the stock ones are.