• If your bottom bracket is a sealed cartridge unit (as most are nowadays), it can't be serviced or adjusted. If it grinds, wobbles, or catches, it must be replaced as a unit. Just remove the old cartridge and replace the entire thing.Bottom Bracket (B.B.s) are the bearing and spindle assemblies that your pedal crank arms spin upon.
• Because of their low and central location, they are constantly being exposed to the worst of contaminants.
• Many B.B.s feature sealed bearing assemblies.However, it does help to keep an eye on their outer shields and keep them as clean as possible, by wiping away any crud with a rag. Also, do not spray pressurized water at the shields.
• Creaking Bottom Brackets. This annoying trait can be caused by a variety of things. All require special tools to fix and are best left to a professional mechanic.