Lower inflation pressures for improved flotation are permitted ONLY if the tire maintains adequate load-carrying capacity at the lower pressure. 20 psi is the minimum recommended pressure for a passenger or light truck tire. Pressures lower than 20 psi may be used off the road when speeds are less than 15 MPH and when the tire has adequate load-carrying capacity at the lower pressure.
The best recommendation for highway use is to follow the inflation pressure specified by the vehicle manufacturer which can be found in the owner’s manual or on the sticker on the inside of the driver’s door.
When installing a different size than the original equipment tire, the replacement tire should be inflated to provide the same load capability of the original tire size at the manufacturer’s recommended pressure.