How to clean brake pads properly to stop squeal?

Question

I bought a new MTB recently that came with TEKTRO HD-275 hydraulic disk brakes, after two weeks it has started to squeal, then I clean both front and back pads with Isopropyl alcohol and 120 sandpaper, now back wheel squeal is okay, but the front wheel squeal is still there?
What should I do? Replace front pads with new, or again clean with Water + Isopropyl alcohol + Rub more with Sand Paper?

Tude Productions · Accepted Answer

BrakClean is the best. Spray on a rag and wipe the rotor and pad. I have rim brakes and am not sure first hand of the benefits of scuffing the pads off the bike so someone else will have to speak on that. However, BrakClean has stopped squeal on my rim brakes without having to adjust toe when they get "contaminated."
On car disc brakes you just have to bed them with several stop from 20 MPH or so to prevent squeals. I am not sure if bike brake pads are the same or if your really need to scuff them with sandpaper. Someone else will need to comment on that who has first hand experience for bikes.

daneb · Answer

Squeal is usually a result of contamination of the pads and/or rotor. If you get any kind of oily or greasy substance on the rotor; it’ll get on the pads and cause squeal. My usual process for dealing with this is cleaning and resurfacing.

Take the pads off and lightly sand with ~150 grit sandpaper. This should get rid of any surface contaminants.
Wipe the pad dust off the pads with a damp paper towel (see choice of liquid below). Let dry.
Clean and resurface the rotors with the wheel on the bike. Isopropyl alcohol or Windex both work and they’re both safe to use with bare hands. Get the sandpaper wet and wrap it around the disc so you can hold it on both sides of the rotor at once. Spin the wheel for a couple of minutes to give the rotor a good clean and resurfacing at once.
Wipe the rotor clean with a wet cloth or paper towel and let dry.
Put a thin coat of grease on the back of the pads before reinstalling to prevent vibration squeals (this is done with cars but some people do it with bikes as well).
Reinstall pads
Bed in the brakes like you with with new pads or rotors.

A couple of situations could lead to persisten squeal:

Deep contamination of the pads. They are somewhat porous so grease or oil can sometimes penetrate deep in the pad so your squeal may last for the life of the pads.
Some brakes are just loud. This is common with metallic pads. Semi metallic (hybrid) or organic pads are much quieter and less prone to squeaking.

How to clean brake pads properly to stop squeal?

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