A piston is a small, moving part inside the hydraulic disc brake system of a bicycle. When you squeeze the brake lever, fluid pushes these pistons toward the wheel. The pistons then press the brake pads against a spinning metal disc called a rotor.
This friction slows the bike down quickly and safely in all weather conditions. Most brakes have two or four pistons working together to provide stopping power. They must move smoothly to ensure the brakes do not rub when you are not pedaling. Over time, dirt can build up around the pistons and cause them to stick.
For example, a mechanic might clean the pistons on a dirty mountain bike to restore smooth braking performance. Properly working pistons provide a crisp feel and consistent control on steep descents. They are the hidden muscles of your bicycle’s modern braking system.
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