Radial tire with tread pattern having four or five circumferential ribs

A pneumatic tire having a tread defining an inner shoulder, an outer shoulder and a tread pattern therebetween, the tread pattern comprising an inner circumferential groove, an outer circumferential groove and at least one intermediate circumferential groove therebetween, the circumferential grooves dividing the tread into four or five circumferential ribs including inner and outer shoulder ribs, inner and outer intermediate ribs between the shoulder ribs and an optional central rib between the intermediate ribs,

• the inner shoulder rib having inner lateral grooves, each inner lateral groove extending from the inner shoulder toward but not reaching the inner circumferential groove, the inner shoulder rib having multiple sipes which are arranged between adjacent pairs of inner lateral grooves, wherein no lateral groove in the inner shoulder rib reaches the inner circumferential groove,
• the outer shoulder rib having outer lateral grooves, each outer lateral groove extending from the outer shoulder toward but not reaching the outer circumferential groove, the outer shoulder rib also having multiple sipes which are arranged between adjacent pairs of outer lateral grooves, wherein no lateral groove in the outer shoulder rib reaches the outer circumferential groove,
• wherein the width of at least one shoulder rib is between about 17% and about 19% of the width of the tread, and further
• wherein the tread defines a void volume ratio and a land-sea surface area ratio, the land-sea surface area ratio being about 4–8% larger than the void volume ratio, and wherein each circumferential groove is a substantially straight groove having substantially straight edges.