Pneumatic tyre tread comprising: a tread part which comes into contact with the road surface when the tyre is rolling, in which is formed at least one main groove having a bottom surface and two opposing wall surfaces (31, 32) and having a depth D and a width W, and a plurality of flexible fences which are intended to collapse under the pressure of water penetrating into the main groove, the plurality of flexible fences having a thickness E which extend inside the main groove in the radially outwards direction of the tyre from the bottom surface of the main groove in such a way as to obstruct at least 70% of the cross-sectional area of the main groove and in such a way as to have a gap from the wall surfaces (31, 32), the flexible fences being disposed at intervals such that at least one of said flexible fences is present inside the main groove within the tread footprint when the tyre is rolling, the pneumatic tyre tread being characterized in that the plurality of flexible fences comprise an inside portion having an end edge part which is connected to the bottom surface of the main groove, and an outside portion which is radially outside a predetermined height D1 from the bottom surface of the main groove, and the average angle of inclination of the inside portion with respect to a line perpendicular to the surface of the tread part in contact with the road surface is greater than the average angle of inclination of the outside portion with respect to a line perpendicular to the surface of the tread part in contact with the road surface, when viewed in cross section parallel to the direction in which the main groove extends and on a plane perpendicular to the surface of the tread part in contact with the road surface, and in that the average angle of inclination of the inside portion of the flexible fences with respect to a line perpendicular to the surface of the tread part in contact with the road surface is greater than 60°, and in that the predetermined height D1 from the bottom surface of the main groove is less than 50% of the depth D. a tread part which comes into contact with the road surface when the tyre is rolling, in which is formed at least one main groove having a bottom surface and two opposing wall surfaces (31, 32) and having a depth D and a width W, and a plurality of flexible fences which are intended to collapse under the pressure of water penetrating into the main groove, the plurality of flexible fences having a thickness E which extend inside the main groove in the radially outwards direction of the tyre from the bottom surface of the main groove in such a way as to obstruct at least 70% of the cross-sectional area of the main groove and in such a way as to have a gap from the wall surfaces (31, 32), the flexible fences being disposed at intervals such that at least one of said flexible fences is present inside the main groove within the tread footprint when the tyre is rolling, the pneumatic tyre tread being characterized in that the plurality of flexible fences comprise an inside portion having an end edge part which is connected to the bottom surface of the main groove, and an outside portion which is radially outside a predetermined height D1 from the bottom surface of the main groove, and the average angle of inclination of the inside portion with respect to a line perpendicular to the surface of the tread part in contact with the road surface is greater than the average angle of inclination of the outside portion with respect to a line perpendicular to the surface of the tread part in contact with the road surface, when viewed in cross section parallel to the direction in which the main groove extends and on a plane perpendicular to the surface of the tread part in contact with the road surface, and in that the average angle of inclination of the inside portion of the flexible fences with respect to a line perpendicular to the surface of the tread part in contact with the road surface is greater than 60°, and in that the predetermined height D1 from the bottom surface of the main groove is less than 50% of the depth D.