BSA has long been the dominant standard. The external cups with bearings are screwed into the bottom bracket shell fitted with threads.
Shimano introduced PressFit to reduce the overall weight.
Pressfit (86.5 mm shell for race and 92 mm for MTB) also known as BB86/BB92. The bearings are placed in plastic housing which are then pressed into the frame (C-Bear poineered in using precisioned cnc metal alloy housing instead of plastic housing), for use with 24 mm cranksets which were originally designed for BSA.
BB30 was introduced by Cannondale, since 2000 became an open standard. In contrast to the BSA standard, the bottom bracket of BB30 frame has no threads. The bearings are directly pressed into the bottom bracket shell, which has a diameter of 42.
BB30 bottom bracket
Width 68 mm (Road) or 73 mm (MTB)
Diameter 42 mm
Compatible for crank spindle: 24, 30 mm and campagnolo
Pressing bearings directly in the frame requires higher manufacturing tolerances of the bottom bracket shell, consequently PF30 was developed, where the bearing sits in a housing, in turn the housing with the bearings are then pressed in the frame. PF30 also known as Pressfit 30.
PF30 bottom bracket
Width 68 mm (Road) or 73 mm (MTB)
Diameter 46 mm
Compatible for crank spindle: 24, 30 mm and campagnolo
Specialized came out with a non-standard PF30 bottom bracket shell (a shortened PF30 shell 61 mm) called OSBB for their carbon race bike.
Later, Specialized expoxied an aluminium insert into the carbon frame bottom bracket, thereby, converting the frame to a BB30.
Specialized MTB bike frame is a standard PF30 bottom bracket shell.
OSBB(61) bottom bracket
Width 61 mm (Road)
Diameter 46 mm
Compatible for crank spindle: 24, 30 mm and campagnolo
BBRight is yet another PF30 variant introduced by Cervelo. It widened PF30 on the non-drive side, increasing the total width of the bottom bracket shell to 79 mm. The assymetric shell allows for a wider connection of the chainstay on the non-drive side for higher rigidity.
BBR bottom bracket
Width 79 mm (Road)
Diameter 46 mm
Compatible for crank spindle: 24, 30 mm and Campagnolo, except BB30 crankset.
Width 86.5 mm (Road only)
Diameter 46 mm
Compatible for crank spindle: 24, 30 mm and campagnolo, except BB30 crankset.
Here the bottom bracket width is 90.5 mm for road and 95 mm for MTB, and the bearings rest direct in the frame.
The latest standard introduced by Cannondale BB30A is used for its Synapse Road frame with a non standard bottom bracket shell of 73 mm versus commonly 68 mm for road frames.
C-bear has a bottom bracket to ensure your chosen bike frame and crank play nicely together. Just Install and Ride. .
When in doubt, just give us a shout. We are here to help you navigate the maze.
Here is C-Bear Bottom Bracket Easy Finder