Bottom Brackets

Threaded bottom brackets are also known as BSA (British Small Arms), BSC (British Standard Cycle) or BC, ISO, British and Euro (BMX brands refer to threaded BB's this way).

There are 3 types of threaded bottom brackets: Adjustable cup-and-cone, Cartridge (integrated axle) and External bearing (use a much larger thru-axle).

Adjustable cup-and-cone styles are designed to be completely dismantled into their separate pieces and services (cups, bearings and axle). They are an older style unit and rarely seen, except on some kids bikes and BMXs.

Cartridge style bottom brackets have sealed or semi-sealed bearings and the axle is integrated; it can't be pulled apart.

This is the style we see on modern recreation bikes. It's used because it lasts much longer and is smoother than the cup-and-cone.

External bearing bottom brackets have notches on the outside to help thread them into the bottom bracket shell.

The crank's axle then slides through. The axle can be anywhere between 22mm to 30mm in diameter.

Press-Fit bottom brackets are pressed into the bike's bottom bracket shell and held there by an interference fit.

The common types are:

PF41. Also known by BB86, BB89.5, BB92, BB107, BB132, Shimano® Press-Fit and PF24. These bottom brackets fit into a BB shell diameter of 41mm.

PF42. As you guessed, these bottom brackets fit into a 42mm diameter bore. They are also known as BB30, BB30a, BB30ai, BBright™ Direct Fit.

Then we have PF46 (46mm diameter bore) that is also known commonly by the names PF30, PF30a, PF30ai, BB386EVO, OSBB, BBright™ Press Fit.