A bicycle ticks when you stop pedalling. Inside the back hub, small spring-loaded pawls lean against a ring of ratchet teeth; while you push, they catch and carry the wheel round without a sound, and the moment you stop and the wheel runs on faster than the gears, they skip over the teeth one by one. So the noise a bike is known for is not the noise of riding it. It is the sound of the rider resting while the bike keeps going, a small machine applauding you for doing nothing.