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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?

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    Just ride it for a bit. You need to bed the pads in still. The noise is a built-in pedestrian warning :)
    – MaplePanda
    Commented Jan 20, 2021 at 4:24
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    @MaplePanda I see yeah, will try to adapt this, even some drivers looking, able to see their wiggly face often :D
    – Kelum
    Commented Jan 20, 2021 at 5:49
  • What pads are you using, and are you riding in the wet or dry? My sintered pads (on the tourer) are silent dry but squeal wet. My semi-metallic (MTB) are intermittently noisy in all conditions
    – Chris H
    Commented Jan 20, 2021 at 12:49
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    @Chris Those brakes come with resin pads.
    – MaplePanda
    Commented Jan 20, 2021 at 16:23
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    @MaplePanda and the OP is presumably using the originals
    – Chris H
    Commented Jan 20, 2021 at 16:24

2 Answers 2

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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.

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  • thanks, mate appreciate this, I visited 2 different bike repair shops before doing this, they refused to replace and asked me to cycle the first 100KM first, but this bit annoying for people since I'm going around the city haha :)
    – Kelum
    Commented Jan 20, 2021 at 2:17
  • @Kelum did just stopping hard a few times work?
    – Tude Productions
    Commented Jan 20, 2021 at 2:21
  • Nope I didn't try it
    – Kelum
    Commented Jan 20, 2021 at 2:25
  • How is this specific pruduct different from.other product or, say, simply isopropyl alcohol? How many products did you compare to be able to say this one is the best?
    – Vladimir F Героям слава
    Commented Jan 20, 2021 at 6:35
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    Note that "rubbing alcohol" is not the same as isopropyl alcohol, or even 70% IPA/30% water. It could be ethanol-based, which isn't a problem, but may contain oils as well as ingredients to make it undrinkable. These can leave a slippery residue on evaporation. IPA-based brake cleaners don't have the same problem (partly @VladimirF)
    – Chris H
    Commented Jan 20, 2021 at 12:54
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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.

  1. Take the pads off and lightly sand with ~150 grit sandpaper. This should get rid of any surface contaminants.
  2. Wipe the pad dust off the pads with a damp paper towel (see choice of liquid below). Let dry.
  3. 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.
  4. Wipe the rotor clean with a wet cloth or paper towel and let dry.
  5. 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).
  6. Reinstall pads
  7. Bed in the brakes like you with with new pads or rotors.

A couple of situations could lead to persisten squeal:

  1. 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.
  2. 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.
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  • A few issues I might see with this: 1: using sandpaper on the rotors is likely to cause excessive rotor wear. 2: Windex is not a hydrocarbon solvent (if I remember correctly) and won't dissolve lipids very well, and may leave a residue. 3: Grease on the back of the pads may soften and liquify when heated and migrate onto the braking surfaces. I fully agree with the rest of the answer though!
    – MaplePanda
    Commented Jan 22, 2021 at 6:28
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    I would agree but I’ve tried all of it myself (except the dab of grease) with good results. This same procedure is fairly common at local bike shops. If Windex causes you concern, use alcohol or a brake cleaner. The grease rally should be a super thin coat, not a dab. A thin coat isn’t going to drip off.
    – daneb
    Commented Jan 23, 2021 at 15:34
  • I'm not sure the smear of grease on the backs will do much good. I've started doing that as rusty backings caused me trouble (bonding to the adjuster for the fixed pad) and the squeal is at least as bad. Mine are metallic and only squeal when wet.
    – Chris H
    Commented Feb 22, 2021 at 16:38
  • Same here. Metallic always squeals. Like I said, I've not done the dab of grease myself, but if applied properly without getting it on the pads, it won't hurt, even if it doesn't stop the squeal.
    – daneb
    Commented Feb 23, 2021 at 18:14

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