Saddle Slang is sponsored by Rehook. Check out our tools, bike care and apparel

BB Shell Width


The internal width of a bicycle's bottom bracket shell.

Example usage: 'My bike has a 68mm BB shell width.'

Most used in: Mountain biking and road cycling.

Most used by: Cyclists and mechanics.

Popularity: 8/10

Comedy Value: 2/10

Also see: BB Standard, Bottom Bracket Spindle Length, Axle Standard, Crank Spindle Diameter,


Understanding BB Shell Width in Cycling

BB shell width is an important term to understand when discussing cycling. This term refers to the width of the frame's bottom bracket shell, which is the opening in the frame that houses the bottom bracket. Bottom brackets are the components that allow the crankset to rotate and the chain to drive the bike forward.

BB shell widths are typically measured in millimeters and range from 68mm to 83mm. The most common width is 68mm, which is used for road bikes. Mountain bikes typically have a 73mm BB shell width, while fat bikes have a 100mm shell width. The width of the shell is important because it determines the type of bottom bracket that can be used with the frame.

The BB shell width is determined by the frame manufacturer and is typically listed in the frame specs. It is important to choose the correct bottom bracket for your frame, as using the wrong type can damage your frame and create other problems. If you are unsure what BB shell width your frame has, it is best to consult with the frame manufacturer or a bike shop mechanic.


The Origin of the Term 'BB Shell Width' in Cycling

The term 'BB Shell Width' is used in cycling to refer to the width of the bottom bracket shell, which is the opening in the frame of a bicycle where the crankset is mounted. The term originated in the United States in the late 1980s, when the first oversize bottom bracket shells were introduced.

Prior to this, bottom bracket shells had a standard width of 68mm, making them compatible with most cranksets. However, some manufacturers began to experiment with wider shells, allowing for more clearance and a larger range of available cranksets. The most common widths for these oversize bottom brackets were 73mm and 83mm.

By the early 1990s, the term 'BB Shell Width' had become widely accepted in the cycling industry to refer to the width of the bottom bracket shell. It is now used to help cyclists determine which cranksets are compatible with their bike frames.

Back to blog

Leave a comment

Please note, comments need to be approved before they are published.

Saddle Slang

Find definitions for all of the technical terms, slang, and acronyms used in cycling. From the different types of bikes and their components, to training techniques, racing terminology and put downs, this dictionary has it all.

Talk the Talk
1 of 3