Bottom Bracket Inspection

It’s tough to determine the condition of the bottom bracket (acronym: BB) without pulling the crank arms and spinning the BB spindle using your fingers. Bottom bracket inspection does take a good bit of effort and some sellers may be put off by a buyer pulling the crank arms. A BB can feel smooth when turned using the crank arms, but I’ve pulled crank arms and found the BB spindle to be nearly impossible to turn using one’s fingers. If you’re not going to pull the cranks the minimum you need to do is make sure there’s no play in the BB. Wiggle the crank arms side to side to check for play. The good thing is sealed BB’s are cheap, starting at about $20, so if you neglect to perform a bottom bracket inspection it’s not the end of the world.

You’ll want to familiarize yourself with the various BB types out there so you know what you’re dealing with when looking at a bicycle. If you do want to perform a bottom bracket inspection, you should familiarize yourself with each type.

Here is a list of common BB types with links to images coming soon, for now I suggest a Google image search (TODO lightbox plugin image links):

  • Cottered (generally you’ll want to convert a bike with cottered BB/cranks to square taper, or just avoid altogether)
  • Ashtabula (one piece, common on cruisers)
  • Square taper (unsealed, popular from 70’s to 90’s)
  • Square taper (sealed, replaced unsealed in 90’s)
  • External (various, came about with 2 piece cranksets)
  • Press fit (fairly new, various)
  • BMX (various, I will not cover any bmx topics)

Add in “how-to” on pulling crank arms?