Decoupling groove for pneumatic tire tread

A pneumatic radial ply truck tire for use on medium truck trailers, the tire including a tread, a casing, the casing having two sidewalls, one or more radial plies extending from, and wrapped about, two annular beads, and a belt reinforcement structure located radially between the tread and the one or more radial plies, the tread comprising:

• a plurality of circumferentially extending tread grooves;
• a pair of circumferentially extending shoulder ribs;
• a pair of radially recessed ribs, the radially recessed ribs being radially recessed and non-road contacting under static load, the recessed ribs being disposed at a lateral edge of the shoulder ribs;
• and
• a pair of circumferentially extending decoupling grooves, each decoupling groove defining a transition between a shoulder rib and a recessed rib,
• a lateral edge of one of the shoulder ribs having a first radius of curvature forming a transition from a radially outer surface of the shoulder rib to a first side surface of the corresponding decoupling groove, a base surface of the decoupling groove having a second radius of curvature forming a transition from the first side surface to a second side surface of the decoupling groove, a radially outer surface of the corresponding recessed rib having a third radius of curvature forming a continuous transition from the second side surface to a third outer side surface of the shoulder portion of the tread,
• the radially outer surface of the recessed rib and the third radius of curvature defining a nub for repelling materials that damage the tread,
• the first radius of curvature being between 4 mm and 8 mm and the second radius of curvature being between 2 mm and 4 mm.