this invention relates to a light weight rubber blend that can be beneficially used in rubber articles , such as power transmission belts and tires . in the rubber blends of this invention a 2 : 1 layered silicate clay , preferably an organophilic 2 : 1 layered silicate clay , is substituted for a portion of the carbon black that is normally used in the rubber as a filler . this can be done without sacrificing the physical properties of the rubber composition in cases where the rubber in the blend contains an amino group . tire tread compounds that utilize such rubber compositions offer increased vehicle fuel economy . this invention also relates to improving the strength modulus and elongation of carbon black and silica filled compounds by the addition of 2 : 1 layered silicate clays thereto without modifying the level of carbon black or silica . such compounds have increased flexibility and tensile strength for tire side - wall applications . this invention more specifically discloses a process for making a vulcanized rubber article comprising the steps of kneading an amino group containing rubbery polymer , wherein said amino group containing rubbery polymer contains from about 0 . 1 weight percent to about 20 weight percent of a monomer containing an amino group , and from 0 . 1 to about 25 phr of a 2 : 1 layered silicate clay which is an organophilic 2 : 1 layered silicate clay ; and conventional rubber compounding ingredients selected at least from the group of curing agents , cure accelerators , cure activators , processing aids , reinforcing fillers , oils , cure retarders , resins , and antidegradants at a temperature within the range of about 70 ° c . to about 190 ° c . in a bulk thermomechanical mixer to produce a mixed compound ; discharging the said mixed compound from the bulk thermomechanical mixer ; forming the mixed compound into an article ; and vulcanizing the article . the present invention also reveals a rubber composition that is comprised of : an amino group containing rubbery polymer , wherein said amino group containing rubbery polymer contains from about 0 . 1 weight percent to about 20 weight percent of a monomer containing an amino group , and from about 0 . 1 phr to about 25 phr of a 2 : 1 layered silicate clay . the present invention further discloses a tire which is comprised of a generally toroidal - shaped carcass with an outer circumferential tread , two spaced beads , at least one ply extending from bead to bead and sidewalls extending radially from and connecting said tread to said beads ; wherein said tread is adapted to be ground - contacting ; wherein the tread is comprised of the rubbery polymer of this invention .