The optimal tire pressure for a given vehicle is typically listed in the owner's manual of the vehicle. The optimal tire pressure for Firestone tires depends more on the vehicle to which the tires are mounted rather than the tires themselves.
In addition to the owner's manual, most vehicles have optimal tire pressure ranges printed on a tire placard attached to the vehicle. This placard is located on the inside of the car door, the door frame, the glove box lid or the fuel door, depending on the manufacturer. Optimal air pressures are often different for tires on the vehicle's front wheels versus those on the rear wheels, particularly if the vehicle uses different tire sizes on the front and rear wheels, as do some performance cars.
Vehicle manufacturers carefully determine the optimal tire design and pressure for their cars when designing the vehicle. This pressure does not vary by manufacturer, so the same pressure range should accompany tires made by Firestone or any other brand. However, there are some circumstances in which drivers may vary pressure within the manufacturer's specified ranges to achieve better performance. For example, under-inflating a tire slightly can increase its surface area and grip on the road, but may also increase tire wear and the danger of a blowout.