Recent 39++ Off Road Tires 17 Inch. Tyres off road biased tyres start around 31 outside diameter, and in these parts fit 16 wheels (land rover dominated market). So, short of that, the big question is, will 20 inch or 17 inch be the difference between me getting across something like this (assuming reasonable all terrain tires on). Tyres 245/70 r17 wrangler duratrac 4x4 off road mud terrain offroad mt 115s.