The front tires on a Ford 8N tractor are size 4.00-19, while the original rear tires are size 10-28. In each of these measurements the first number is the width of the tire, while the second is the diameter of the rim.
Ford introduced the 8N in 1947. It was the third and final variant of the Ford N-Series farm tractors and the top-selling tractor of all time in North America. The 8N differed from its predecessor, the 2N, by having a four-speed transmission instead of a three-speed, better power and a new paint scheme. Ford replaced the N-Series with the Ford NAA in 1953.