Conservation. Truck tires runs 146,000 miles. This truck tire has run 146,000 miles. It is now planned to retreat it with a life expenctancy of at least half the original mileage. The tire is size 9.75 x 20, weighs 129 pounds and was run at an air pressure of 70 pounds. Miss Jean Spanitz, stenographer in the Division of Motor Transportaion, Office of Defense Transportation, poses with the tire