Bottom Bracket Interface

There are many different interfaces that allow a bottom bracket to be installed into the bottom bracket shell of a frame. 

Here are a few questions that should be asked when trying to figure out bottom bracket compatibility.
- Is the bottom bracket shell threaded or pressfit?
- How wide is the bottom bracket shell?
- What diameter is the bottom bracket shell?
- What kind of crank spindle is being used?

There are many different combinations of bottom bracket traits; many of these combinations have adopted a name to make it easier to identify.

For example:
- BB92 refers to a pressfit bottom bracket shell with a diameter of 41mm and a width of 92mm.
- BB86 refers to a pressfit bottom bracket shell with a diameter of 41mm and a width of 86.5mm.
- PF30 refers to a pressfit bottom bracket shell with a diameter of 46mm and a number of possible widths depending on the manufacturer.
- BB30 refers to two different interfaces which can create lots of confusion. As a bottom bracket interface it refers to a pressfit bottom bracket shell with a diameter of 42mm and a width of 68-73mm. BB30 also refers to a crank spindle interface with a diameter of 30mm.
- BSA refers to a threaded bottom bracket shell with a diameter & thread pitch of 34.8mm x 1.06mm and a width of 68-100mm.