A constant contact side bearing assembly configured for insertion into a walled receptacle on an upper surface of a railcar bolster. The constant contact side bearing assembly includes a housing defining a cavity and a spring. A cap is positioned by and overlies an end of the spring. The cap is mounted for reciprocatory guided movements by and relative to the housing, with a generally flat railcar body engaging portion on the cap being positioned relative to the housing and the walled enclosure by the spring. The side bearing assembly further includes an apparatus for securing the housing of the side bearing assembly within the walled receptacle on the railcar bolster.