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Just found a tiny metal ball in my bike fiddling corner. I haven't worked on any ball bearing since the last cleaning, so I'm a bit confused where it might have dropped out of. It's pretty exactly 3mm in diameter. Is there any chance to infer which ball bearing it may have dropped out of at some point?

  • How old is your bike? – Criggie Mar 10 at 18:57
  • parts from all over the last 9 years. – pseyfert Mar 10 at 21:13
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    At least now people know how to wind you up, leave small bike parts near your work area and make you worry where they might have come from 😛 – Swifty Mar 11 at 13:28
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Pedals usually have 1/8". Depending on how you measured the diameter, maybe that's what you found. I think you'd notice fairly significant play in the pedal for a ball to have fallen out though.

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    I used a slide rule and the ball is just a little bit smaller than 1/8", but I'll check the pedals anyway. – pseyfert Mar 10 at 21:14
  • Pedals do have small bearings, but that means they have a lot of them, so loss of one is probably insignificant overall. Giving the pedals the flick test and seeing how long they spin for may show one that stops quicker. BUT that doesn't indicate which one might be missing a bearing due to less resistance. If a bearing got our then it should have some play on it. – Criggie Mar 10 at 23:33
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You can always start with Sheldon for some ideas of what bearings are used where, 1/8” includes pedals, headsets, freewheels. Watch out for obsolescence tho. Freewheel might imply freehubs too.

Sealed/cartridge bearings can have some pretty small bearings in too and they can be found all over bikes. However, I think you would know if you’d taken something like that apart and spilled the bearings.

Short of taking the likely suspects apart to check, I’m not sure of the value in inferring where it’s from - it could be from somewhere else completely anyway!

  • Thanks for the link, from the slide rule I thought it's just a little bit smaller than 1/8" and matched 3mm perfect, but since there's nothing for 3mm in the table I'll check for where 1/8" balls should be. – pseyfert Mar 10 at 21:18
  • Swifty makes a good point about the bearing possibly coming from anywhere. It may have fallen out of when you were last working on the bike, and it's been there all along. And there's no way to know if it came from the bike or if it just came out of the bag/container that you had the bearing balls in – Gaston Mar 11 at 12:07
  • Might have not even been off the bike! An old bearing will wear down fractionally so could measure 3.00mm>x< 1/8” – Swifty Mar 11 at 13:26

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