A railroad car constant contact side bearing assembly including a housing, a top cap arranged for vertical reciprocatory movements relative to the housing, and a spring accommodated in a spring cavity defined by the housing and cap for resiliently urging the top cap into frictional sliding engagement with an underside of a railcar body. At least one of the side bearing housing and cap is formed from a high performance plastic material whereby enhancing the vertical reciprocity of the cap relative to the housing.