Bottom bracket: The bearing system the pedals (and cranks) rotate about. Includes a spindle to which the crankset is connected plus the bearings on their own. You will find there's bearing surface area about the spindle, and on Every from the cups that thread in to the frame. Alloy refers https://bikeenginesforsale26025.onzeblog.com/35064938/engine-bike-conversion-kit-options