GB1451812A - Pneumatic tyre - Google Patents

Abstract

1451812 Pneumatic tyre treads FIRESTONE TIRE & RUBBER CO 16 Nov 1973 [8 March 1973] 53438/73 Heading B7C A pneumatic tyre has a tread comprising at least one V-section groove 2 at least one sidewall 7 of which makes an angle of at least 18 degrees with the normal to the road-contacting surface of the tread and contains recesses 6 each having an end wall 11 and two sidewalls 12, each end wall 11 in the unworn tread, Fig. 1, meeting the road-contacting surface of the tread at the junction between this surface and the associated sidewall 7 and diverging from the sidewall in a radially inward direction whereby, as the tread wears-Fig. 2, edges 9 formed where the sidewalls 12 of the recesses are caused by wear to meet the road contacting surface increase in length. The edges 9 thus act to compensate for the loss in tread grip resulting from the decrease in effective width of the or each V-section groove caused by tread wear. In the illustrated embodiment the tread comprises two parallel-walled zig-zag circumferential grooves 3, and two zig-zag circumferential V-section grooves 2 each having recesses 6 in both sidewalls, the recesses in one sidewall being offset, as shown, or aligned with those in the other widewall. The illustrated grooves 2 are symmetrical in section but the or each V-section groove may alternatively be asymmetrical (Fig. 4, not shown). The end wall 11 of each recess may be perpendicular to the road-contacting surface of the tread as shown in Fig. 3 or may be at an acute angle. The or each V-section groove may alternatively extend axially of the tyre. The spacing between adjacent recesses 6 in the same groove sidewall may be 0À1-0À25 inches and the width of the recesses 0À04-0À1 inches.