Actually Skeets, it is more that because the front tires flex so much from turning that if you run tubes in your tire to load them, the tubes can't stand the extra friction and will wear holes in them. When tractor manufacturers started putting FWA (Front Wheel Assist) as the early 4 wheel drive tractors like Kubota has on the market, loading the front tires is what many dealers did for extra weight to counterbalance heavy 3pt hitch loads and extra traction. We had a couple on the farm like that, and the front tires were always going flat from tube failure. It is also a problem with radial rear tires on larger tractors using tubes for loading. On side hills with a lot of sidewall flexing, we would have many flats. Solution to the problem is use more steel weights.