Refurbishing the front calipers is a relatively straight forward job.
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You just need to be careful that you don't scratch/mark the
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"front" of the pistons
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(ie the part nearest the pads/seals) when cleaning them.
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Other than that it's just a case of stripping down, cleaning, replacing the seals and rebuilding them.
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The pistons can sometimes be a bu88er to get out though, if that's what's causing the caliper to stick.
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Are you sure it's the pistons and not the sliders though? If you remove the suspect caliper from its mounting frame, you should then be able to move the frame back and forth.
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If you can't then it's the sliders that have seized
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(more common tbh).
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