An investigation of four experimental and two conventional 75-millimeter-bore (size 215) cylindrical-roller bearings was conducted over a range of DN values (product of bearing bore in mm and shaft speed in rpm) from 300,000 to 2,300,000, radial loads from 7 to 1613 pounds, and oil flows from 2 to 8 pounds per minute with a single-jet circulatory oil feed. The four experimental bearings were equipped with outer-race-riding cages and inner-race-guided rollers. One conventional bearing was equipped with an outer-race-riding cage and outer-race-guided rollers, while the second conventional bearings was equipped with an inner-race-riding cage and inner-race-guided rollers. Each of the six test bearings was equipped with a different design cage made of nodular iron.