]I have 255/85 on the standard rims for my touring set.  I've had the BFG KM2 and found them OK, but prone to chipping. 
The rear tyres only lasted about 30,000km before they were basically unusable.  We had to change the rear tyres over before crossing the Great Victoria desert - just not worth the risk.  We could only get a pair of Maxis Bighorn MT's in Carnarvan and  so far they have been great,  done over 20,000km on pretty bad roads with them now with the the same load and no evidence of chipping or any excessive wear.  These are what the KM2 looked like.  
 
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