Bottom Bracket Shell. 68,BSA
The Bottom bracket shell is the part of the frame that holds the crank bearings. Three key items are Width, Diameter and Threading. Diameter and Threading are almost always BSA (British standard). The width is most commonly 68mm, but there are some that are 70 or 73. For purposes of compact reports, the width and threading are combined. Example: 68,BSA or 73,BSA, or PressFit See tables at the following: BSA 24 68 ShellType - A BB bearing type requires a certain shell type - the inner spindle diameter is a characteristic of the crank, not the shell. The crank spindle most definitely expects bearings of a certain size and spacing. It will require a certain type of shell Some carbon frames now are designed to have the bearings "press fitted" into the frame. These bikes follow a different standard.
See separate document. The common threaded bottom bracket uses cups or adaptors with the thread specification of 1.37" x 24 threads per inch (approximately 34.8mm diameter). The most commonly used term for this standard is "English" threading, sometimes abbreviated as ENG. Also known as "BSA" or Standard threaded. BSA means "British Standard
- In the above, 68 is the Width, and BSA tells you both the diameter and threads.
https://wheelsmfg.com/crankset-tech
https://wheelsmfg.com/bb-standards
ShellType ShellD Width Thread
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Mega Exo 24 68
BB30 42
386 EVO 46
- there is definitely a thing called a FSA Mega Exo cartridge, which is the bearing setup. The crank is a separate part. So the three entities are:
BB Bearing type
Crank Type
- A Crank model requires a certain BB Bearing type (Sq Taper cartridge)
A shell t