Patent ID: 8447578

Claim:
A method of designing a tire having a circumferential tread, the method comprising: identifying a target residual aligning torque range for a tire having a buttress portion and a non-zero buttress angle (β) on each side of the tire, wherein the buttress portion extends from a sidewall of the tire to an outer boundary of the circumferential tread, and wherein the non-zero buttress angle (β) is an angle between the buttress portion and a plane that contains an axis of rotation of the tire; creating a computer model of the tire that includes the non-zero buttress angle (β) comprising: generating, based on a compression mechanism applied to the computer model of the tire with the non-zero buttress angle (β), a tire shear force (F ts ) and a road shear force (F rs ) to balance a moment created from a road normal force (F r,n ) which is offset at a distance (D 1 ) to a counteractive tire normal force (f tn ); generating, based on a coupling shear stiffness mechanism applied to the computer model of the tire with the non-zero buttress angle (β), a reactive buttress fore or aft force (F bfa ) and a reactive road fore or aft force (F rba ) to balance a moment created from a road lateral force (F rl ), which is offset at a distance (D 2 ) to a reactive buttress lateral force (F bl ); and generating a tire reactive shear force (Ftrs) at an edge of the tire footprint based on the compression mechanism and the coupling shear stiffness mechanism; calculating a residual aligning torque of the computer model of the tire with the non-zero buttress angle (β), the calculated residual aligning torque being based on the tire reactive shear force (F trs ), which includes the effects of the non-zero buttress angle (β); comparing the calculated residual aligning torque value to the target residual aligning torque range; determining whether the calculated residual aligning torque value is within the target residual aligning torque range; adjusting the tire reactive shear force by adjusting the non-zero buttress angle (β), which changes the tire reactive shear force (F trs ) in the computer model of the tire with the non-zero buttress angle (β); repeating the calculating, comparing, determining, and adjusting until the calculated residual aligning torque value is within the target residual aligning torque range; and producing a final tire design.