Well.......... do you reckon if you optioned the heavier spring pack on a Sandman that you had to have the heavier duty tyres and then it went from XX7 to XU3(thats the other Sandman number I hope:o) and it wasnt the the different tyres at all, it was the spring set?
Makes sense to me as the tyres wont carry the load as the springs have to be uprated as well. Not much point in having a big load and having the arse dragging on the ground.