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I have a new (old) bicycle, and I am in the process of disassembling it.

I arrived to the bottom bracket (with a cottered crank), and unscrewed the ring without problems, but then I'm faced with a part that I don't think I've seen before (circled in yellow in the picture below, the part next to the frame with the threads and a strange "groove").

Bottom Bracket

I've disassembled several BB, but this is new to me (normally I have a nut and unscrew it, I bet this may be another kind of nut), and I don't know if this can be removed and how?

Is this something that I can unscrew, and does anyone know of the technique/tools to do it?

(By the way, the other side has the same part, but as far as I can see there is no thread (visible at least))

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    That is the cup. The question is, which way does it unscrew? The answer is: The same direction that the lockring unscrewed. (The rounded shaft suggests this is an old cottered crank design, not seen since about 1980.)
    – Daniel R Hicks
    Mar 18, 2014 at 16:08
  • @DanielRHicks thanks Daniel! that is indeed important to know. I was going for the "lets try the standard (non-drive = unscrew right to left as normal) and drive not standard (unscrew to the right)".
    – jackJoe
    Mar 18, 2014 at 16:19
  • With bottom bracket threads it's really unpredictable. And with that sort of wrench deal you want to be sure, rather than round off everything vainly trying to go the wrong direction.
    – Daniel R Hicks
    Mar 18, 2014 at 16:23

2 Answers 2

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It's a bottom bracket cup. There are specialty tools you can use to remove it such as the HCW-11 on this page, or if it isn't rusted in, you can probably accomplish the same with an adjustable crescent wrench. Under there are some ball bearings, so make sure you don't lose any when you open it up. The bearings should be in a cage, which would stop you from losing them, but with an older and worn bike such as the one shown in the picture, the bearing cage may be broken.

enter image description here

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  • Thanks for the tip, I already knnew about the ball bearings, I didn't know of a proper tool for the disassembly, since the outer part is so low compared to any other "normal" nut shapped BB. I'll give it a try with an adjustable crescent wrench first.
    – jackJoe
    Mar 18, 2014 at 14:47
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    There are also more desctructive ways of removing it if you are just replacing, and you can't find other methods to get it out.
    – Kibbee
    Mar 18, 2014 at 15:16
  • I already saw that one, if my drive side doesn't come out I'll go for something like that! thanks again for the extra tip :)
    – jackJoe
    Mar 18, 2014 at 16:15
  • UPDATE: I applied HD40 and unscrewed the non-drive side without problems with an adjustable crescent wrench (normal unscrew direction, right to left); the drive side is more stubborn, I'll let it soak in HD40 and try again tomorrow, the ridges are lower in this side.
    – jackJoe
    Mar 18, 2014 at 19:03
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This is the «cup-and-cone» bb type. This means the part you have unscrewed is the lockring, and the mystery part is a bb cone.

This type off bb is very like to cone-based hubs (like Shimano ones). You can use vise (bolt clamp) to operate with this type of bb, but be careful if you want to put it back after disassembling.

cup and cone BB

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  • Thanks for your answer! I will assemble it later, so I'll be careful.
    – jackJoe
    Mar 18, 2014 at 14:47

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