Kubota used a powder-coated rim on the BX and when you add Rim Guard to the wheel and tire and the air pressure gets low, the Rim Guard will get between the tire bead and the rim, causing the tire to stand still and the rim will be spinning inside the tire. Move the tire valve to 12 o'clock and inflate to 20 pounds or even a few more if the rim continues to slip inside the tire. Also, if you have the old rubber tire valves, it is only a matter of time before one will break and you will lose all your ballast. I suggest taking the tire off the tractor and laying it down with the valve pointed up. Then using a bead breaker, break the bead on the valve side, and then pull the old valve out with a valve puller and replace it with a bolt-in valve. There is enough room to push the tire down and slip the new valve stem into the rim hole, and get the nut onto it. Tighten the nut and then inflate the tire before lifting. You might have to remove the core to get enough air rushing into the tire to seat the bead. Reinstall the valve and fill it with air and put it back on the tractor.