Bluffer’s GUIDE-

BRACKETS BOTTOM

Threaded (BSA)

This is the most common BB type.The bearings are housed in cups, which are threaded into the frame’s BB shell, using a relatively inexpensive tool. Spacers allow the BBs to be used with 68mm, 73mm and DH-width BB shells, and they can accommodate most 24mm and 30mm-diameter crank axles.

PF30

PF30 was developed by SRAM in an attempt to solve some of the issues with BB30. Here, the bearings are housed in nylon cups, which are pressed into a 46mm-diameter BB shell. In theory, this makes it easier to install and more tolerant to frame manufacturing inaccuracies than BB30.

BB30

BB30 was developed by Cannondale to shave weight and add sti ness, by eliminating the frame threads and using a 30mm axle.The bearings are pressed directly into a 42mm-diameter BB shell.This demands careful fitting and tight manufacturing tolerances, or the bearings are prone to creak or wear out early.

PF41 (BB92, etc)

As with PF30, the bearings are housed in nylon cups, which are pressed into the frame. BB shells can be 89.5mm, 121mm or (commonly) 92mm wide.This broader stance puts less stress on the bearings than PF30 or BB30. Due to a narrower BB shell diameter of 41mm, not all 30mm-axle cranks are compatible.