Thanks all. To be clear, I'm no hero, I was very surprised when the can grounded and it certainly wasn't near the edge of the tyre.
I have about 40mm under the tyre when on the centre stand, so it seems I need to takle some rear suspension adjustment.
I can see that the cans can be lifted quite a bit if I take the panniers and hangers off, but I'd rather not do that as the panniers were a key reason for buying an ST, they mean I can do many more miles (where previously carrying kit mean't I had to take the car).
I'll see if I can find the right knob to increase ride hieght (you may notice I'm new to suspension adjustment) and hopefully I'll then be able to have fun down my favourite B roads without leaving bits of my bike attached to them.
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