What is the standard safety limit (minimum tread depth) for road motorcycle tires in typical utility and underbone operations?

1. 1.0 mm (or when the tread wears down to the built-in wear indicators).
2. 0.1 mm (or when the internal nylon cord becomes visible).
3. 4.0 mm to 5.0 mm.
4. Tires do not have a tread depth limit as long as they hold air.