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I know that squealing brakes are fairly typical questions but I have not found a solution yet.

My bike is a Haibike with Tektro Auriga Comp hydraulic disk brakes and in recent years I ride in southern Finland.

During past winter, my front brake started squealing a lot. This was pretty usual in wet conditions, so I didn't pay much attention and assumed the winter conditions might have an effect on it.

However, months on, I still have this problem and it is pretty annoying to wake up the whole neighborhood any time I need to brake.

Today I performed bleeding of both hydraulic brakes and also replaced the braking pads in both brakes. Rear works perfect, front feels the same as before - braking performance not so sharp as rear and squeals during hard braking and/or low speed.

One thing that's "special" in my case is that my rear brake has not worked for a year or two because I didn't want to bleed the brakes (and Finland is flat), so the front brake has definitely been used much more.

Now the first thing on everybody's mind will be brake pad contamination, but the brake pads are new and I paid extra extra care not to get them in contact with any dirt or oil.
I tried cleaning the disk with soap to make avoid any oil but no improvement.

Could it be that the disk is the problem? I read advices to make it a bit more coarse with a fine sandpaper, could that help?

I'm happy for any hints, thanks!

  • Happens to me during the winter months or after rainy days, too. It tends to quit for the rest of the ride after the first brake or two, so I've started just pulsing my brakes hard when I notice it happen in order to "convince" them to not squeal anymore. Does yours persist, or does it stop like mine? – Ian MacDonald Apr 2 at 15:54
  • What type of pads do you have? My metal ones always squeal in the wet but are fine in the dry. The ones on the other bike (unknown compound, assumed organic) don't – Chris H Apr 2 at 15:54
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    @Czechnology Cool username. 😊 – David Richerby Apr 2 at 17:09
  • I would try disc-specific cleaning compound, not soap. Well that's not true. I don't mess with contaminated anything with my discs (call me paranoid) and I'd just buy new rotors and pads. – Paul H Apr 2 at 18:07
  • Contamination won't just be on your brake pads, but on the rotor as well. – Carbon side up Apr 2 at 21:00
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Presuming you were thorough with your cleaning and the rotor was left with no residue of any kind (I achieve this on rotors I suspect of being oil or greased contaminated by either using brake cleaner or by finishing with alcohol if I'm using detergent/soap), and also presuming the front caliper isn't having a fluid leak that's causing oil to immediately contaminate the system even after cleaning (pull the pads you just installed and check everywhere for oil, particularly behind the back plates where the pistons contact), it sounds like a lot of the symptoms of the front rotor being glazed.

A glazed rotor is caused by overheating and will cause both noise and diminished power. There are ways of sanding down and breathing new life into them, but just replacing them can often make more sense, especially on a basic one with some years of regular use on it anyway. You could do a simple test and swap your rear onto the front, assuming they're the same size.

  • Thanks Nathan. I could try some better cleaning methods (do you just get high percentage ethanol from pharmacy?). I don't thing there is a leak, the insides looked dry and hydraulics stayed firm for years, but I can check again. I am trying to stay away from rotor change (if possible) because I think that properly aligning it will be a pain. Could you elaborate on the sanding approach - if it makes sense trying it out? – Czechnology Apr 2 at 21:59
  • High percent ethanol is fine, as is denatured alcohol (mix of methanol and ethanol) or isopropyl alcohol/isopropanol. Definitely having one of those in your repair gear is pretty key for disc brakes. To sand them, the technique is a little bit different depending on how bad it is, but the main thing you're trying to accomplish is sanding an even amount all around no matter what. Usually I do it with the wheel on a truing stand and with the rotor pinched in my hand, grasping it with sandpaper and spinning it, careful not to cut yourself. – Nathan Knutson Apr 2 at 23:28
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    Let me stress though that in the case of a heavily used Tektro rotor, I really would be thinking about just replacing it. It may be time to do so for thickness/wear issues anyway. – Nathan Knutson Apr 2 at 23:29
  • Brake cleaner from the car workshop works fine! – Carel Apr 3 at 9:04
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You haven't mentioned checking the caliper alignment. If the pads and disc aren't exactly parallel the braking can feel weak, presumably as the disc is forced sideways by the pads. I've found that it can provide a surprisingly big improvement, and is worth doing when changing the pads.

Adjusting the caliper alignment is simple. Park Tool have a great walkthrough on the process. To summarise:

  1. Loosen the caliper mounting bolts so the brake caliper is free to rotate.
  2. Squeeze the brake level so the pads contact the disc. This should rotate the caliper to the correct alignment.
  3. While holding the lever, tighten the mounting bolts. Be careful when tightening not to twist the caliper. I've found it best to alternate between the bolts until reasonably tight, then finishing off with a torque wrench (6-8 Nm). Having a helper to hold the lever makes this much less awkward!
  • Welcome! Nice suggestion, if you are able to summarise the process that would help protect against the link expiring in the future too – Swifty Apr 8 at 11:07
  • Thanks, Askell, I have done exactly that when I was changing the pads and bleeding, so that shouldn't be the issue. – Czechnology Apr 14 at 14:27

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