For the Nissan Altima 2.5 S, 2.5 S AWD, 2.5 SL, and 2.5 SL AWD trim levels, the correct tire size is P205/65 R16.
If your Nissan Altima has the 3.5 SE or 3.5 SER trim levels, the correct tire size will be P225/55 R17.
It is important to use the correct tire size as specified by the vehicle manufacturer in order to ensure proper handling and performance of your vehicle.