For some days now I am observing the decreasing performance of my disc brakes on my MTB. Additionally, braking is extremely loud (squeaking). I don't think I have oil or fatty substances on the discs. Still I can't exclude that.

  • So what do you think is the problem and how can I solve it?

I would guess I have to change the brakeshoes but I am not sure.

  • How can I check the actual problem without wasting time/money?
  • If I have to apply new brakeshoes, how is this done safely?

My brakes are hydraulic: Shimano Deore BR-M596.


2 Answers 2


There are a number of simple things you can do to try improve performance before replacing the brake pads.

  1. Check the pads to see how worn they are. Here is an example of a new and worn pad requiring replacing.

image from park tools

If the pads don't appear to need replacing you can:

  1. Lightly sand the pad with fine sand paper
  2. Clean the rotor with isopropyl alcohol (or any non-residue solvent)

If that eliminates the squeaking but doesn't improve performance the next step is to bleed brakes. If you have Avid similar brakes the process (similar for Juicy and Elixirs) is more involved than the Shimano process and make require professional assistance.

  • Thx for your answer. I will check those infos for the Shimano process. Edited my model of brakes. Jul 18, 2014 at 19:07

Hydraulic brakes' pistons need to be cleaned "every couple of month". If not, the dirt soaks the brake fluid and contaminated the brake pads. Also, a dirty piston can get stuck and then doesn't work anymore.

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