The correct pressure settings for your vehicle can be referenced in the owner's manual or on the placard found inside the drivers door jamb. The information will provide a recommended cold temperature setting that is to be used regardless of the tire size or manufacturer as long as it is properly load rated for your vehicle. The tire itself, has a maximum psi that is not to be exceeded on a cold inflation reading. It is always best to check tire pressures first thing in the morning before driving the vehicle. This is the point when you will find the truest reads and can maximize the pressure settings on all corners of the vehicle
Maintaining the correct tire inflation rates will help maximize tire performance and fuel economy, which allows drivers to experience optimal comfort, durability and performance designed to match the needs of their vehicle.
Might I recommend a few useful air gauges by Accutire that are helpful in maintaining proper tire inflation settings:
Digital Set Point Programmable Air Gauge with Light
Digital Pencil Air Gauge with Tread Depth Gauge