Identifying bottom bracket type Looking to buy an eccentric bottom bracket for adjusting the chain tension, however before ordering need to make sure it is compatible with my bb shell.


There are following types of eccentric BB:

For 1.37” x 24T &amp; Width 68mm BB Shell
For BB Shell I.D 46mm &amp; Width 68~73mm (JIS BB Only)
For BB Shell I.D 46mm &amp; Width 68~73mm (Shimano &amp; SRAM Compatible)

Need help choosing the right one (i can do additional measurements if needed)
Looks like you have a standard 'English' or ISO standard threaded bottom bracket shell. These have 1.37 inch (34.8mm ) diameter threads of 24 threads per inch. Common width for road bikes is 68mm You can easily verify this by measuring the inside diameter of the shell and the width.
You might also have a 'Italian' threaded shell that has slightly smaller threads. See https://www.sheldonbrown.com/cribsheet-bottombrackets.html
For 'three piece' type cranks where the axle is part of the bottom bracket you also have to consider the axle length. Cartridge bottom brackets typically come in a range of axle lengths and the correct length must be selected so that the crank chainrings have the correct chainline (distance from center of the frame to the chainring).