referring to the drawings , fig1 and 2 illustrate an idler pulley 10 comprising a molded plastic body 12 having an integral tubular bearing carrier insert 14 centrally positioned in the pulley body 12 . the tubular bearing carrier insert 14 is incorporated between the plastic body of the pulley and an outer bearing race 15 of bearing 16 . the bearing 16 may be fitted into the insert either before or after molding . the idler pulley 10 of the invention may be from a wide variety of polymeric materials , provided that they are distortion resistant at ambient and higher temperatures . it also is generally desirable , particularly for automotive applications , that the polymeric materials used to make the pulley 10 have a low - temperature resiliency . suitable polymeric materials include thermoplastic and thermosetting materials , such as polyamides , e . g ., polyphthalamides , nylons , particularly , nylon - 6 , nylon - 6 , 6 , nylon - 4 , 6 ; nylon 6 , 10 ; nylon 9 ; nylon 11 and nylon - 12 ; polyesters , epoxy resins ; phenolic resins ; polyurethanes ; high density polyolefins , e . g ., polyethylene ; and the like . the polymeric material used to manufacture the body 12 of the pulley 10 may be compounded with additional fillers , modifiers or reinforcing agents as determined for a particular application . in a preferred aspect of the invention the polymeric material contains a reinforcing material , such as a fibrous glass reinforcing material . useful modifiers include lubricants such as polytetrafluoroethylene , silicone , graphite , molybdenum disulfide , ultra high molecular weight polyethylene . other suitable modifiers include thermoplastic materials , rubber , etc . fillers may be glass beads , carbon black , minerals such as calcium carbonate , wollastonite , mica , clay , talc , etc . the reinforcing agent may be glass fibers , long glass fibers , aramid , carbon fibers , etc . the outer peripheral surface of the pulley 10 comprises a plurality of protrusions 20 and recesses 22 . the protrusions may be in the form of v - shaped projections and recesses , truncated v - shaped projections and recesses , and any other useful design . in a preferred aspect of the invention , the peripheral surface of the pulley 10 comprises a metal or ceramic liner 18 to provide enhanced abrasion resistance . the liner 18 may be of any suitable material which has the desired resistance to abrasion , and is sufficiently deformable so that it can be used in the practice of the invention . steel or aluminum having a thickness in the approximate range of about 0 . 010 - 0 . 050 inch is preferred . the tubular insert 14 may be manufactured from steel , aluminum , zinc , brass , or any other suitably rigid and strong material . and may contain additives such as one or more modifiers , fillers , reinforcing agents , adhesion promoters , and the like . useful modifiers include lubricants such as polytetrafluoroethylene , silicone , graphite , molybdenum disulfide , ultra high molecular weight polyethylene . other suitable modifiers include thermoplastic materials , rubber , etc . fillers may be glass beads , carbon black , minerals such as calcium carbonate , wollastonite , mica , clay , talc , etc . the reinforcing agent may be glass fibers , long glass fibers , aramid , carbon fibers , etc . the insert 14 may also be coated or plated to enhance adhesion to the particular polymeric material selected for the body 12 of the idler pulley 10 . for example , a brass or zinc plating over a steel tubular insert shell increases the chemical affinity of the insert for a thermoplastic phenolic material , especially if the phenolic material also incorporates any of several classes of adhesion - enhancing ingredients such as sulfur , silica , acrylates , vinyl acetates , low molecular weight polyamides , etc . the outer surface of the tubular insert 14 may contain interlocking means 13 such as knurls , splines , indents , holes , and the like to provide an irregular outer surface of said tubular insert 14 be knurled , splined , or otherwise shaped , e . g ., it may contain holes , to provide a rough surface for the purpose of enhancing the mechanical interlock of the insert 14 with the plastic body 12 . the inner surface of the tubular insert 14 may be provided with means 24 , such as a stepped profile or detents , to accurately locate and align the bearing 16 during assembly , or the surface of the insert during molding . referring now to fig3 - 5 , the idler pulley 10 is formed using a three - section mold ( or a two - section mold for flat pulleys ), designated generally by the reference numeral 26 . the first , or base section 28 has a cylindrical center portion 30 having an outside diameter approximately equal to the inside diameter of the tubular insert 14 . the second section 32 has at least two segmented sections 34 so that the completed pulley can be easily removed . the segments 34 , when in the molding position , form an annular opening . the inner periphery of the segments 34 has a plurality of projections 36 and recesses 38 corresponding to the shape of the recesses 22 and projections 20 , respectively of the peripheral surface of the pulley 10 . the third section 40 has a central opening 42 which has an inside diameter approximately equal to the outside diameter of the tubular insert 14 . the third section 40 also has at least one injection port 44 through which the plastic material is injected into the mold 26 . the mold sections may be clamped together by any suitable clamping means , such as bolts 45 , as illustrated . to make the pulley 10 , the second section 32 is assembled on the first section 28 and the tubular insert 14 is inserted over the cylindrical center portion 30 of the first portion 28 and the third section 40 is assembled on the top of the second section 32 and the mold 26 is clamped together by the clamping means . the pulley 10 is made by injecting a suitable polymeric material through the injection port ( s ) 44 under sufficient pressure , e . g ., about 500 - 30 , 000 psi , to fill the cavity and , if present , to deform the metal liner 18 , causing it to conform to the projections 36 and recesses 38 in the segments 34 . various changes and modifications may be made to the idler pulley having an integral bearing carrier insert of the present invention , and to the method of manufacturing such idler pulley in light of the above disclosure without departing from the scope and spirit of the appended claims .