Standard bicycle bearing ball sizes - article comments


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To prevent article pages from being miles long, but preserve all the useful questions and answers provided over time, I've decided to copy/paste the website comments to the forum - and "move" further discussions here.

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Standard bicycle bearing ball sizes
  1. Dmitry
    23/04/2017 at 13:01
    Thank you. Very helpful to know. Of course, this info might be found on internet somewhere, but i appreciate that you put such info together for readers’ convenience.
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    Tom Cavaliere Jr.
    04/06/2019 at 18:08
    Having worked in a ball bearing plant for over 20 years. A grade 25 is round within 25 millionths of an inch, and within a given lot the ball to ball diameter variation is within 50 millionths of an inch. Likewise, a grade 10 is is round within 10 millionths of an inch and ball to ball diameter variation within a lot is 20 millionths. The convention is twice the roundness typically.
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    16/11/2019 at 14:18
    Where to find size of bearings for Fuji S10S 1974 used for the bottom bracket (crank bearings)?
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      16/11/2019 at 14:29
      I don’t know.
      If Google doesn’t help, suppose the only way is to measure the existing ones – if they are at hand.
      Maybe someone who knows will chime in.
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    Robert David Taczynski
    24/12/2019 at 19:35
    surface roughness
    egg shapeness
    thought I learned a new word today…wawiness
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    23/05/2020 at 18:01
    This is very helpful and you have solved my problem of what size my bearings are so I can buy replacements.
    Thank you. Stuart
  1. Joe Todd
    23/06/2020 at 05:16
    This is a good piece of information. Thank you for sharing. I have French pedals from the 1940s, with ball bearings that I measure as 3.15mm. Everything else on that bike is non-standard, (thread pitch, bottom bracket, stem diameter, post diameter,….). Maybe the pedal bearings were uncommon too. I am still searching for new ones of the correct size.
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      21/07/2020 at 19:44
      3.15mm as measured is likely just to be standard 1/8″ balls, I would have thought…
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    Anthony Bourland
    28/08/2020 at 15:29
    I recently purchased a 26inch Beinaiqi cavalier fat bike, my question is, can I put cartridge bearings in my rear hub or should I stay with the cup & cone system ?
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      28/08/2020 at 18:41
      I don’t know how one would put cartridge bearings into a hub with cup and cone bearings (or vice-versa for that matter).
      The usual way of achieving that is getting a different hub.
      But I wouldn’t sweat it too much – cup and cone bearings are relatively easy to service and can last a long time if serviced regularly (generally: once a year, or each 5000 km, whichever comes first).
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    22/02/2021 at 00:57
    Thanks for summing all this up nice and succinctly. Most useful article I’ve read all day!
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    23/04/2021 at 12:50
    in australia alot of people just throw old bikes into the street when they cant be bothered to fix them,i totaly strip older bikes for parts and sometimes i even find a nice spare bike to fix up,i re-use bearings,cassettes handle bars you name it,i even find new tubes and tires that are thrown away.
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    14/07/2021 at 21:40
    Great explanation, thank you!
    This article just saved me a lot of time, I overhauled the wheels of 3 bikes at the same time last week , and today
    I found a ball stuck to my shoes, ~6.3mm in diameter. Where does it belong? It’s not from my old Peugeot, they use thin hubs and smaller balls. Not from the front of Raleigh, that should be 3/16″ (~4.8mm), so it should be from the rear of Raleigh! Just one wheel to open and insert the wheel, a 10 minutes job! In my defense, the bearing on the cassette side looks smaller, at the time it seemed logic to have 8 balls instead of 9.
  1. Andy
    19/08/2021 at 09:04
    Thanks for the advice on loose bearings, the bearings in my Shimano hubs are held in a cage, can I just put new bearings in the old cage? If I can source non Shimano bearings in a cage is it enough to just match the dimensions of the cage or do they come with different profiles to fit into the hub races?
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      20/08/2021 at 08:52
      Hi Andy,
      I suppose you could use the old cages with new balls.
      However, I prefer tossing the cages out and putting more loose bearing balls (more will fit once the cage is out).
      An exception to that are hubs that have a huge amount of bearing balls that are too fiddly to fit one by one.
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    23/08/2021 at 09:00
    cages are only made to make it easier to install bearings,they serve no other purpose,bearings run alot better without cages,those cages allways cause problems,fine bearings in cages around steering stem i only use as those bearings are just to fine to install whithout a cage.when using loose bearings leave a space,you fill the whole space with bearings then you remove one or two bearings so there is a space,if you dont leave a space between those bearings they will grind away and not run smoothly
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    23/08/2021 at 11:17
    Thanks Mike and Relja for your replies, I shall discard the cages.
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    29/08/2021 at 00:46
    Good article, but 3/32 is 2.381, not 2.281mm 😉
    greetings from Poland
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      29/08/2021 at 07:42
      Hi Lukasz,
      Thank you very much for the correction. If you notice any other mistakes, don’t hesitate to not them. It’s appreciated. 🙂
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    27/07/2022 at 20:23
    What about stainless steel bearings for hubs? Are they better then regular?
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      Relja Novović
      28/07/2022 at 07:10
      Hi Mantas,
      I don’t think they are better for bicycle bearing use.
      Grade 25, 52100 chrome steel (not chrome-plated) is as good as it gets (and makes sense in terms of cost-benefits) for the application.
  1. mike
    30/07/2022 at 06:51
    i use enduro grade 25 bearings they are the best ones,any harder bearings will only wear down the cones,the grade 25 ones last a very long time
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    04/10/2022 at 12:08
    Wow, great website. I knew nothing about bearings but wanting to start servicing my old GT bike myself, this website has helped me understand everything I need to know. Thanks!
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    19/11/2022 at 13:31
    Thanks Relja for taking the time for putting this information together! Very detailed and helpful!
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    19/11/2022 at 18:03
    Hi Relja
    Would the following be ok for a Shimano rear hub?
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      Relja Novović
      19/11/2022 at 20:23
      Hi James,
      Those are G100 bearings. I would prefer G25 quality.
      However, it is fair to say that I have used G100 without any problems (except that the bearings don’t feel as smooth, though that is very subjective).
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    19/11/2022 at 20:26
    Hi Relja
    I will go for the G10 option then, they don’t seem to have a G25 option.
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      Relja Novović
      20/11/2022 at 08:06
      Hi James,
      I think that’s a good idea – and that is exactly what I’ve been using over the past… almost 10 years.
      The only decent-quality bearing balls I can source locally are G10. They are still a lot cheaper than “Shimano original” bearing balls and work without any problems (both on my bikes and on the… not sure how many bikes I’ve serviced over the years). 🙂
03/05/2023 at 10:40
Thank you for your great article.
I intend to buy G20, 52100 chrome steel bearing balls. According to the online store, their hardness is between 60 and 66 HRC. Are they too hard?
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