Pneumatic tire

Claim 2

A pneumatic tire of the type having a radial ply carcass, a tread portion and a cord reinforced belt, the improvement comprising: when said tire is in the configuration in which it was cured said tread, as viewed in planes containing the rotational axis of the tire, has a depression in the central portion thereof, said depression being defined by a smooth curve having a maximum depth which is between 0.005 inch and 4,000 TAW/(T(cos Alpha eff)3AR) + ( Alpha eff/1,000) + (1/M) inch where TAW equals the tread arc width, T equals the belt strength, Alpha equals the effective cord angle of the belts, AR equals the aspect ratio, and M equals the modulus of elasticity of the cords in the belts; and, when said tire is inflated to design inflation pressure and unloaded, said tread has a positive radius of curvature at the mid-circumferential centerline.

Claim 3

A tire as claimed in claim 1, wherein said tire when in the configuration in which it was cured said tread has a pair of raised portions disposed one each on laterally opposite sides of said depression, the point at which each said raised portion is tangent to a common straight tangent parallel to the rotational axis of the tire being spaced from the mid-circumferential centerplane of the tread a distance equal to at least one-third of the distance from said mid-circumferential centerplane of the tread to the lateral edge of the tread.

Claim 4

A tire as claimed in claim 2, wherein the distance from the mid-circumferential centerplane of the tire to said tangent point of each said raised portion is defined by the equation 1/2 (TAW -SR -D) where W equals said distance, TAW equals the tread arc width, D equals the depression, and SR equals the shoulder radius of the mold.

Claim 5

A tire as claimed in claim 3, wherein the radius of curvature of said depression is defined by the equation R1 (D2 + W2)/3D wherein R1 equals said radius of curvature of said depression, and D equals the depth of said depression at said mid-circumferential centerplane, and the radius of curvature of each said raised portion is equal to one-half of the radius of curvature of said depression.

Claim 6

A tire as claimed in claim 1, wherein said depression is equal approximately to

Claim 7

A tire as claimed in claim 4, wherein said depression is equal approximately to

Claim 8

In a method of making a pneumatic tire of the type having a radial ply carcass, a tread portion having a positive radius of curvature at the mid-circumferential centerline when the tire is inflated to design inflation pressure and unloaded and a cord reinforced belt: the improvement comprising; placing the tire in a mold; forming the tire in a toroidal configuration; forming a circumferentially extending smooth depression in the surface of the tread in the area of the mid-circumferential centerline; forming a pair of circumferentially extending raised portions in the surface of the tread one each on laterally opposite sides of said depression, said depression being defined by a smooth curve having a maximum depth which is between 0.005 inch and 4,000 TAW/(T(cos Alpha eff)3AR) + ( Alpha eff/1,000) + (1/M) inch where TAW equals the tread arc width, T equals the belt strength, Alpha equals the effective cord angle of the belts, AR equals the aspect ratio, and M equals the modulus of elasticity of the cords in the belts; and curing said tire while maintaining the aforedescribed configuration.

Claim 9

In a method of making a pneumatic tire of the type having a radial ply carcass, a tread portion having a positive radius of curvature at the mid-circumferential centerline when the tire is inflated to design inflation pressure and unloaded and a cord reinforced belt: the improvement comprising; placing the tire in a mold; forming the tire in a toroidal configuration; forming a circumferentially extending smooth depression in the surface of the tread in the area of the mid-circumferential centerline; forming a pair of circumferentially extending raised portions in the surface of the tread one each on laterally opposite sides of said depression, said depression being defined by a smooth curve having a maximum depth which is between 0.005 inch and 4,000 TAW/(T(cos Alpha eff)3AR) + ( Alpha eff/1,000) + (1/M) inch where TAW equals the tread arc width, T equals the belt strength, Alpha equals the effective cord angle of the belts, AR equals the aspect ratio, and M equals the modulus of elasticity of the cords in the belts; and curing said tire while maintaining the aforedescribed configuration.

Claim 10

A method as claimed in claim 7, wherein each said raised portion is tangent to a common straight tangent parallel to the rotational axis of the tire at a point spaced from the mid-circumferential centerplane of the tread a distance equal to at least one-third of the distance from said mid-circumferential centerplane of the tread to the lateral edge of the tread.

Claim 11

A method as claimed in claim 8, wherein the distance from the mid-circumferential centerplane of the tire to said tangent point of each said raised portion is defined by the equation 1/2 (TAW -SR -D) where W equals said distance, TAW equals the tread arc width, D equals the depression, and SR equals the shoulder radius of the mold.

Claim 12

A method as claimed in claim 9, wherein the radius of curvature of said depression is defined by the equation R1 (D2 + W2/3D) wherein R1 equals said radius of curvature of said depression, and D equals the depth of said depression at said mid-circumferential centerplane, and the radius of curvature of each said raised portion is equal to one-half of the radius of curvature of said depression.

Claim 13

A method as claimed in claim 7, wherein said depression is equal approximately to

Claim 14

A method as claimed in claim 10, wherein said depression is equal approximately to