When installing new rotors do they have to be turned first or are good go out of the box?

Rotors, when newly purchased, should be resurfaced or turned before being installed. This ensures that the rotor surface is smooth, flat, and free of any unevenness or blemishes. Resurfacing or turning the rotors also creates a new braking surface, allowing the brake pads to properly bed into the rotors. In some cases, rotors that are included as part of a brake kit may come pre-turned, eliminating the need for additional resurfacing.