A long travel constant contact side bearing for railway cars provides better handling characteristics, achieving improved tracking and curving through use of various combinations of features. Such a long travel side bearing is able to meet recent stringent American Association of Railroads standards, such as M-976. Lowered spring rates, preferably less than 6,000 lb/in., help with stability and reduce set-up sensitivity. Reduced cap and base dimensions and spring design help achieve travel of at least 5/8''. A visual inspection windows allows ready inspection. Increased service life and wear characteristics are obtained by addition of hardened wear surfaces, improved tolerances, changes to Grade E steel, increase of top contact surface flatness and coped top surface peripheral edges. Standardized sets of spring components can be mixed and matched, requiring fewer specialty parts. Interchangeability of improper components can be prevented by a combination of keying features and/or spring lockout features.