Show determining LIFE OF TIRE ordinarily the more air the longer it will last safe to start with 20 pounds the life of a tire Is the air it contains the more air ordinarily the longer the life of course there are exceptions but it Is a safe rule to start with 20 pounds of air pressure to the cross section inch and if more Is needed to add to it thus a three and a half inch tire will require 70 pounds and a four inch tire 80 pounds road load and speed are determining factors in the pressure required |