As it turns out I bought four tyres but only because I was overoptimistic about the life left on the rears.
However, checking around on the way other 4x4 systems work, I can find zero justification for the 'you must always change all four tyres' mantra trotted out by the tyre changing shops (nearly said garages...)
However, checking around on the way other 4x4 systems work, I can find zero justification for the 'you must always change all four tyres' mantra trotted out by the tyre changing shops (nearly said garages...)