What is a motorcycle wobble, and how should you respond?

1. A normal vibration — ignore it
2. A rapid side-to-side oscillation of the front wheel; grip the bars firmly, do not chop the throttle, gradually close the throttle to slow, and pull off to inspect tires, suspension, and load
3. A vibration that goes away if you accelerate hard
4. A normal feel on a metal bridge grating