Tech Tips from The Bike Barn: Sealed Bottom Brackets
Many bikes today have sealed bottom brackets. This means that all the parts normally put individually into the bottom bracket have been placed into a cartridge. Sealing these parts reduces maintenance of the bottom bracket by sealing out dirt. Such a cartridge also makes repairs much easier; however, sealing the parts in a casing also means that if one part goes bad, the whole cartridge must be replaced, a more expensive procedure than replacing parts individually.