Water pump bearing divided into 2 types by internal features; double-race-ball type(ball/ball) and ball/roller type. Load resistance is the principal difference of "ball" from "roller". "Ball" locating on a "spot" excels in low noize at high speed. "Roller" in linear support endures more radial load and increases load rating. "Roller" is preferred in driving pulley and/or when a load, such as a fan coupling, is installed at off-set position in front.