Noisy disc brake?

Alan O

Über Member
Location
Liverpool
Yesterday I changed the tyres on my hydraulic disc-braked MTB, which obviously meant removing and replacing the wheels.

On my first test ride, I could hear a tick-tick-tick... sound from the front wheel, the kind of sound you get when there's a bit of crud stuck somewhere that's catching once per revolution. But there was no crud I could see anywhere.

I then noticed that it goes away if I depress the front brake lever slightly - not enough to engage the pads, just a very light touch. And it comes back when the brake lever is fully released. If the brake pads were catching on one part of the disc, I guess that could make such a sound - but I don't see how using the brake lever would make it stop.

Does this sound familiar to anyone?
 

Jody

Guru
Does this sound familiar to anyone?

Yes happens every now and then on mine, my guess is if you check the disc will be slightly warped.
 
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Alan O

Alan O

Über Member
Location
Liverpool
Yes happens every now and then on mine, my guess is if you check the disc will be slightly warped.
Thanks, but I've checked the disc and it seems perfectly flat to me. Also, I've been checking it again today, and the noise is actually happening all the way round rather than at just one point, and is quite loud - not sure if that's changed since yesterday or I just couldn't hear it properly when I was actually on the bike.

It seems really weird that depressing the brake lever very slightly makes it go completely silent as the wheel keeps spinning - as it's pushing the pads towards the disc. And the brake works fine for actually stopping.

I guess I'll need to inspect the brake/disc/pads a bit more closely to see if I can work out what's happening.
 

Siclo

Über Member
Sounds very familiar, in my case it's when the pads don't sit square when the piston is fully retracted, the tiny touch of the lever causes the piston to square up the pads, the usual fix is take the pads out, clean all the rubbish out of the caliper, clean the back of the pads, carefully apply a tiny smear of copper-slip to the back of the pads (care not to contaminate the pads), re-fit pads and re-centre caliper.
 
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Alan O

Alan O

Über Member
Location
Liverpool
Sounds very familiar, in my case it's when the pads don't sit square when the piston is fully retracted, the tiny touch of the lever causes the piston to square up the pads, the usual fix is take the pads out, clean all the rubbish out of the caliper, clean the back of the pads, carefully apply a tiny smear of copper-slip to the back of the pads (care not to contaminate the pads), re-fit pads and re-centre caliper.
Thanks, it sounds like that's what I'll have to do - I must have knocked and displaced a pad when I reinserted the disc in the caliper. I'm beginning to regret swapping tyres now. It was only to try a different pair that I could have tried on a non-disc bike, and I was thinking "It'll only take a few minutes - what can go wrong?" :wacko:

Actually, that's something gone wrong with the brakes on every occasion when I've taken the wheels out. The previous time I managed to get a bubble in the brake fluid.

And on another occasion I wanted to try a second set of wheels, but I just couldn't get the discs to line up precisely enough and I gave upon that.

Much as I love the stopping power of discs, I'm starting to wish I had simple and nearly indestructible cantilevers on this bike.
 
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Alan O

Alan O

Über Member
Location
Liverpool
And... I've taken the front wheel off again and I tried cleaning around the caliper/pad as best I could without taking the pads out. I pumped the pad out a bit with the brake lever and pushed it back again manually a few times and it felt smooth enough. And after carefully putting the wheel back, it seems quiet now!

So yes, I must have displaced the pad/piston and/or got some grunge in there - thanks folks. I'll try it on the road later.
 

I like Skol

A Minging Manc...
It was probably the action of removing and reseating the wheel that has sorted the alignment. This is where thru axles have the advantage over traditional qr's. With a normal qr axle they don't always land back in the exact same spot as before. Even changing the tension in the qr or pointing the lever in a different direction when tightening can affect brake alignment. I find consistency is the key.
 
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Alan O

Alan O

Über Member
Location
Liverpool
It was probably the action of removing and reseating the wheel that has sorted the alignment. This is where thru axles have the advantage over traditional qr's. With a normal qr axle they don't always land back in the exact same spot as before. Even changing the tension in the qr or pointing the lever in a different direction when tightening can affect brake alignment. I find consistency is the key.
Yes, I guess it could well have been just that. A quick ride on it this evening and it's fine.
 
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