Do you have some rebar left? If so take about 6 pieces 4 ft long and bend a loop in one end. Drive them in the ground all the way down to the loop, 3 in front of the pile and 3 in back. Take some heavy trot line cord (or cable) and go from one loop in back through the tires and tie it to the front loop. Repeat until all are tied down. Then take a couple sacks of quickceret mix it up and put one shovel full in each tire away from the holes drilled in the tires. The last step will make the tires float , if at all , with the holes up so any air can escape.