A tread is configured to have three rows of tread elements, a center row and a pair of shoulder rows, the center row forming a circumferential rib positioned at an equatorial centerplane of the tread. Each shoulder row has a repeating circumferential array of upwardly extending elongate groove fingers, adjacent groove fingers within the repeating array of each shoulder row of groove fingers being connected by at least one laterally extending channel. An array of serrations line each longitudinal side of the channels, each serration defined by inward tapering serration sidewalls extending to a serration base surface. Each channel is submerged below an outward tread surface such that the submerged channel will emerge as the tread wears down.