Thanks Clive,
I was discussing with Clive, about his Pig problem and suddenly remembered that about four years ago, I was working on a GMC at a customers. He had the local tyre company out at the same time, to apply one of these balancing bead mediums, into the front tyres. His friend had also had it done sometime before and was impressed with the results. Other than that, I have not had any other experience of it, but am sure it is a practical way of balancing large wheels and tyres.
As an aside, many years ago, Bedford MK trucks in service were suffering steering shake at a particular speed. In Workshops, we had a rig to balance the front wheels on the vehicle. What always worried me was the amount of weight that had to be applied to balance, and if it were to fly off. By blowing the beads into the tube, it is a much better idea.