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Mountain bike problem. Please help.

Derp

Derp

May 29, 2013
157
144
#1
Hi TBers, I've noticed this huge MTB thread and since there are so many bike addicts, I hope to get some help.

HORRIBLE DISC BRAKE SQUEAL!
I ride a 2012 Scott Aspect 10, brand new from the shop. It has Shimano Deore Hydraulic Disc Brakes. After not riding it for some time now, those almost brand new brake pads(haven't ever spilled any brake fluid or anything else, look very thick) stop the bike but with a very disturbing loud squeal. What can it be?
 
#5
Ziltoid said:
Asked my tech about it, he told me it wasn't anything unusual and that sometimes it goes away with use, sometime it doesn't. I stopped worrying about it. I think I asked around here once, but I don't recall if I got an answer.
Click to expand...

This is exactly what my tech told me "Ride for a while, it should go away"
 
#7
Derp said:
Hi TBers, I've noticed this huge MTB thread and since there are so many bike addicts, I hope to get some help.

HORRIBLE DISC BRAKE SQUEAL!
I ride a 2012 Scott Aspect 10, brand new from the shop. It has Shimano Deore Hydraulic Disc Brakes. After not riding it for some time now, those almost brand new brake pads(haven't ever spilled any brake fluid or anything else, look very thick) stop the bike but with a very disturbing loud squeal. What can it be?
Click to expand...

I used Deore hydros for years with no appreciable noise unless they were wet so that seems a bit abnormal and I don't think noise is a systemic issue with the newer ones.

Are they the factory brake pads? If so, I'd try replacing them first. Factory pads tend to be pretty crappy and upgrading them will likely make them work better and quiet them. I'm fond of Brake Authority pads but there are lots of others to chose from (EBC, etc.) If that doesn't make it go away, there's probably an issue with the rotor. Brake pad replacement is pretty cheap so it's probably worth giving that a go.

I freakin' hate noisy brakes. I went through a pile of different Avids and couldn't ever get them quiet. I finally sucked the cost up and went with Hope and couldn't be happier with them.
 
#9
1: It may go away with some use--things may have oxidized a bit as it was sitting.

2: Are you sure everything is functioning properly? The discs are centered, and the pistons work evenly?

3: Shimano brake pads are awful. Consider Jagwire. Cures many squeals.
 
#10
The squeal is a resonance.
There are two approaches to dealing with it. One usually works...

One approach is to lubricate the back of the pad and the piston with a moly-bearing high-melting-point grease such as Swepco 101 or a moly-based assembly lube. CV joint grease is also a good choice. This approach minimises the squeal by making everything smooth so there's not enough energy to make sound.

The other approach is to use an adhesive to stick the pad to the piston so it can't move and create sound. We're not talking JB Weld here - it's more like an RTV or contact cement - it won't interfere with your getting the pads off when it's time to replace them. This stuff is usually available at the FLAPS.
 
#11
My Avid BB-7s recently got ALL noisy on me- my method: Apply the brake(one at a time, you'll need two hands), loosen both mounting bolts(the ones that hold the caliper, not the adapter if you have one)& while still applying, re-tighten. Spin the wheel- if theres no rubbing, ride it and see if the noise is gone. If there is noise, squeeze the brake, watching from above- if your rotor moves slightly as the pads grip it, the caliper is too close to the rotor(rubbing, indicated by a rubbing, metallic sound)and needs to move a couple of hairs away from the direction the rotor is moving. This part is hard to get *just right*... were talking less than 1/32 of an inch usually. Anyway, this procedure has worked for me, although sometimes not. I've also been advised to squirt water onto the brake/rotor while braking(tricky), w/sometimes good results.
 
#12
You should hear the loud squeaks the rim brakes make on the ground rims of my trials bike.

But I don't mind, it's kind of reassuring and gives me a little peace of mind. I know that when the sharp loud squeaks start to soften it's time for a new grind.

BTW, I also occasionally get squeals with my disc brake bikes. No big deal to me.
 
#13
It can be a couple of things :



- The caliper may be un-aligned vertically.
Do the Bassteban trick

- Not all frames are created equal , your brake tabs on your frame may not be perfectly parallel to the center line , facing tabs with the right tool will probably fix the problem.
(not all shops have this tool)


-If that doesn't change , it may be contaminated pads.

-if nothing above works , get a pair of Hope brakes. ;)
 
#14
ArtechnikA said:
The squeal is a resonance.
There are two approaches to dealing with it. One usually works...

One approach is to lubricate the back of the pad and the piston with a moly-bearing high-melting-point grease such as Swepco 101 or a moly-based assembly lube. CV joint grease is also a good choice. This approach minimises the squeal by making everything smooth so there's not enough energy to make sound.

The other approach is to use an adhesive to stick the pad to the piston so it can't move and create sound. We're not talking JB Weld here - it's more like an RTV or contact cement - it won't interfere with your getting the pads off when it's time to replace them. This stuff is usually available at the FLAPS.
Click to expand...

+several. This used to be a very common problem with early motorcycle disc brakes. In my experience, one or the other of these solutions always worked (or at least minimized the problem). In fact, Yamaha used to make a very nice silicone based grease for this very problem; still have the little jar in the garage, somewhere...:D
 
#15
Most brake squeal is from the pads grabbing/releasing and lack of stiffness in the caliper mount. If you were to grip the caliper when it squeals, you'd feel vibrations. Clean the rotors and pads with brake cleaner and see if it helps- the material used for the pads can absorb moisture and become dusty- neither of which helps you stop.

This reminds me of a saying about sports cars- Americans don't care if their brakes stop the car, as long as they don't squeal and Europeans don't care if they squeal, as long as they stop the car.
 
#18
Derp said:
Have you ever tried to solve it?
Click to expand...

A car?




:D

Sorry, couldn't help it.




The squeal is a vibrating resonance in the parts, not unlike what a speakers tweeter does on purpose. Could be due to any number of mechanical tightening needed, some design flaw where brake and rotor don't work well together, some other hydraulic mismatch where the system pressure vs. the parts ability to "absorb" such pressure or the pushing end being to soft it's "springing back"/ not strong or consistent enough to make the pad/rotor/wheel behave, etc.

Moisture will also do it. The pad/rotor will grip-let go-grip-let go....really, really fast.....almost like anti-lock brakes done poorly.
 

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