I ran Nitto mud grapplers in a 35/12.50/18 e range tires on spyderlocks. I was at about 10psi in rock gardens to get the sidewalks to flex. Even then they didn't flex like my MTR Kevlars do at 15psi, but the Kevlars suck in the road and I actually prefer my old mud grapplers. I loved those tires.