Patent ID: 7891391

Claim:
A tire having a rubber tread comprised of an outer tread cap layer and an underlying specialized transition tread rubber layer; wherein said tread contains a tread base rubber layer underlying said specialized transition rubber layer; wherein said outer tread cap rubber layer is comprised of a lug and groove configuration with raised lugs having tread running surfaces and grooves positioned between said lugs; and wherein said transition rubber layer contains particulate pre-cured rubber and coal dust, wherein said outer tread cap rubber layer and said tread base rubber layer are exclusive of particulate pre-cured rubber and coal dust, wherein at least one of said tread grooves extends radially inwardly through said outer tread cap layer into a portion of, and not entirely through, said transition tread rubber layer and said groove is thereby a part of said transition tread rubber layer; wherein said tread transition layer rubber is comprised of, based upon parts by weight per 100 parts by weight rubber (phr): (A) elastomer(s) consisting of 100 phr of at least one diene-based elastomer; (B) from about 5 to about 50 phr of combination of ingredients, comprised of a combination of particulate pre-cured rubber and coal dust, and wherein said tread transition layer rubber contains from about 40 to about 120 phr of filler reinforcement selected from rubber reinforcing carbon black, wherein said transition tread rubber layer extends radially outward into and within at least one of said tread lugs to include from about 5 to about 50 percent of the height of said tread lug extending from the bottom of at least one tread groove adjacent to at least one side of said tread lug, and wherein at a least a portion of said transition rubber layer is positioned within at least one of said tread lugs of said outer tread cap rubber layer in a manner to become a running surface of the tire upon at least a portion of said lug of said outer tread cap layer wearing away to expose said portion of said transition rubber layer.