Off-road tires are typically with thick, deep tread. On dirt surfaces, the exposed edges of the tread dig into soft ground to give more traction than rolling friction alone, These off-road tires provide their maximum grip on loose surfaces, but on paved surfaces the smaller contact patch affords less traction as compared to street tires.
Some off-road tires are designed to be used with low inflation pressure on difficult terrain, reducing their rigidity and allowing the tread to better conform to the terrain.