Specialized Hardrock - How to stop disc brakes from squealing? I have a Specialized Hardrock 2011 Disc brake mountain bike with a front brake that squeals when used lightly.  It's OK if I use the brake hard - but I usually don't need or want to stop in such a hurry!  I have been using the rear brake more for light braking, which is something that I don't like to do because the front brake is best for this.  

It has been like this pretty much  since the day I got it, so I initially put it down to needing running in.  It has got a bit better with time and a few hundred miles, but not much - I try not to brake and instead carry the momentum of the bike where I can for increased efficiency.

What should I look into adjusting to stop disks squealing?
In my experience disc break squeal is typically a result of excessive vibration caused by one of three things:


Contamination - Brake disc and pads should only be cleaned with isopropyl alcohol.  Give them a thorough wipe down.
Poor adjustment/loose components - Try looking at the manufacturers web site for adjustment and torque specifications.  Installing and adjusting brakes is one place where a torque wrench can be helpful.
Lower end brake components - A lot of lower end disc brake sets have variations in the pads and rotors that just naturally encourage a squeal.  Sometimes as they wear it will diminish, but often you are stuck with the sound unless you want to fork out the money to upgrade.


Note that especially in case 2 and 3 you will see the behavior you describe where the squeal is worse when the brakes are applied lightly.  As you apply more force you remove the ability of the involved parts to vibrate.