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.

enter image description here

enter image description here

There are following types of eccentric BB:

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

Need help choosing the right one (i can do additional measurements if needed)

  • AFAIK there is no room in this size shell for a eccentric chain tension adjustment. Can you provide links to the products you have found? Aug 10, 2020 at 10:34
  • @Argenti Apparatus, yes, here it is. youtu.be/yWmxxeGn00A and the product: firstcomponents.com/buy-here Aug 10, 2020 at 15:02
  • That product is an external bearing type that works with 'two-piece' cranks. Presumably you are changing the crank as well. I have to say I do not like the look of that product as it seems it would be very easy to get bearing misalignment which will create drag and accelerated wear. Aug 10, 2020 at 15:21
  • @Argenti Apparatus, does it only work with two-piece crankset? Also, this seems to be my only way to adjust the chain tension since it's a fixed gear on a road bike frame. sjscycles.co.uk/bottom-brackets/trickstuff-excentriker also, here someone apperantly used it for 5000km with no issues, so maybe it just requires more time to get a good alignment. Aug 10, 2020 at 15:36
  • > does it only work with two-piece crankset? Correct. You have a 'cartridge' BB: the axle is part of the BB and is attaches to the cranks with a square taper interface. The BB you linked to needs a crank with the axle attached to the drive side crank, presumably a 24mm Shimano type. Aug 10, 2020 at 16:40

1 Answer 1


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).

  • If width is 68mm that would exclude Italian, which have 70mm shell width. Just to keep it simple
    – Swifty
    Aug 10, 2020 at 14:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.