Abstract: There is disclosed tires for motor vehicles each having a tread provided with a plurality of large convex portions and small convex portions, the convex portions and the small convex portions being differentiated in heights and areas thereof, the small convex portions being disposed around the large convex portion for forming a plurality of normal pyramidal structures. The normal pyramidal structures are formed by disposing the large concave portion around the small concave portion. There is formed a reversed pyramidal structure by disposing the large convex portions around the small convex portion.

Abstract: There are disclosed several sliding devices. One sliding device comprises a sheet mounted on a slope and having a descending substrate, a plurality of recesses arranged uniformly on the substrate, a plurality of balls engaged in the recesses for supporting the ski and rotatable in full directions, the plurality of balls being exposed over the substrate so that the ski contacts the balls, and projecting edges provided at peripheries of the recesses on the substrate for preventing the plurality of balls from getting out from the recesses.