The invention relates to pneumatic tires having treads of a cap/base configuration where the outer tread cap rubber layer contains lugs with intervening grooves which extend to the running surface of the tread cap and wherein at least one of said grooves is contained in a rubber block within the tread. For this invention, the tread groove-containing rubber block joins the tire carcass and extends radially outward through the tread base rubber layer and into the outer tread cap rubber layer.