ABMA standard 9 and ISO 281 give equations for calculating the “Basic Dynamic Radial Load Rating” for ball bearings. These equations are based on a number of assumptions, many of which are not valid for thin section bearings (ref. ABMA Standard 26.2). A white paper from Kaydon Bearings explains a better method for calculating Dynamic Radial Load Rating for thin section ball bearings, using contact stress, number of stress cycles per revolution and five years of actual test results. These equations can also be used to calculate the Dynamic Radial Load Rating for four-point contact ball bearings, which are not covered in Standard 9 or ISO 281.