Pneumatic tire and tread therefor having variable rolling contact with the ground

A high speed pneumatic tire comprising a tread having a road contact central portion symmetrical to an equatorial plane of the tire;

• first and second shoulder portions being spaced respectively, laterally of the central tread portion by a continuous circumferentially extending groove and at an angle to the central portion within the range of 10 to 30.degree., the shoulders each having a tread of a radially variable lesser extent than the central tread portion;
• the first and second shoulder portions forming with the central portion the entire width of the tread surface, the tread surface forming said first and second portions having a width in variable contact with the road;
• a reinforcing breaker located under the tread extending transversely under the first, second and central portions;
• said breaker comprising at least one layer having marginal free edges folded back toward the equatorial plane to form folded back portions radially external of an intermediate portion of the breaker layer, each having a folded edge;
• each of said folded back portions having a width at least equal to the width of a respective one of the shoulder portions;
• each said folded back portion located under one of the respective shoulder portions;
• each folded edge extending laterally only into a respective shoulder portion;
• said breaker further comprising an annular supplementary ply layer, the folded back portions being folded around respective marginal free edges of the supplementary ply layer.