A body in motion wants to stay in motion. It's Newton's first law and a fixed subject in physics classes, but applied to the motorcycle it primarily means that you need good brakes to bring things to a hold.
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Brake discs combined with brake pads and brake drums with brake shoes are the braking systems you'll come across on motorcycles. They may seem complex, but both the brake discs, the brake pads and the brake fluid are fairly easy to replace yourself.
What you do yourself, you often do better, and besides, it keeps the costs of maintenance down. One thing though; consult an expert when in doubt. Newton's first law is not something to take lightly while riding your motorcycle.