This invention relates to a method and apparatus for maintaining equal air pressure in a pair of tires on a work machine. The invention provides a valve body with a pair of piston chambers. A piston is reciprocatably positioned within each piston chamber, the pistons are biased toward a first closed end of the piston chambers. The closed end of each piston chamber is connected by a passageway to one of the tires. Each piston chamber is additionally fluidly connected to the other piston chamber. When the air pressure in each tire is above a predetermined amount the pistons are moved away from the closed end of the piston chamber and airflow is permitted between the piston chambers thereby balancing the tire pressures. If the pressure in either tire is below the predetermined minimum, the piston in that respective piston chamber moves toward the first end to block, airflow between the piston chambers.