Dad and I used to break the bead on tires (haywagons, baler, rake, truck, etc) with the hydraulic drawbar on the back of his Farmall 200. The fast hitch generates plenty of downforce- just place the tire to be "unmounted" flat on the ground centered under the drawbar. Place a block of wood (~12" 2x4) with 2 square ends at the edge of the rim and up against the underside of the drawbar. Slowly lower the drawbar and the sidewall will be pushed away from the bead! Be careful not to use too long a block of wood or keep pushing after the bead is broken as you will raise the rear of the tractor off the ground with the hydraulic!
Frank