Brake callipers are generally fitted with springs and pins which allow the pads to move freely without rattling and vibrating excessively. They are also fitted with shims between the backing plate and the calliper piston. All these items are fitted in order to eliminate noise, however, due to the dynamic nature of your brake system, these pins, springs and shims wear and lose their tension which can result in brake noise. Worn and scored brake discs can also result in brake noise particularly if new brake pads are fitted without skimming the discs.
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