You should go by vehicle manufacturers specifications for the load range tire installed. The max pressure listed on the sidewall is not the recommended running pressure, only the max pressure the tire is rated for. Changing to an aftermarket tire does not affect the recommnended tire pressures, unless a heavier tires is installed thant oem (like going from a P rated tires to a C range LT tires). Now, having said that, you may need to run the pressures a bit higher if there is a handling or wear issue, using the factory spec as a guideline.
