Wider tires can be run at lower pressures because the increased footprint will support more weight. I run big apple 2.35 on snowcat rims and can run them at 25psi unloaded and I will add enough air to not risk pinch flats and to avoid squirrely handling when I carry a load. When I put my skinnier studded tires on in the winter, I need to bump up the pressure to arround 45psi.