วิธีแก้แบบ short term อ่านเองนะครับไม่ว่างแปล
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Short term solution:
Unhook the handbrake cable from the pivot arm, spray WD40/penetrant around the area and work the pivot pin its entire range of movement. Then apply a waterproof grease (Castrol CL) to the area and work that in. It is possible on relatively new calipers to remove the pivot-pin & spring: in such cases replace the pivot-pin and seal, and thoroughly clean & lubricate the pivot-pin needle-bearing area.
Finding that lubrication is only a short-term resolution correlates with the cause being deteriorated rubber-seal & needle-bearing inside the calliper.