Standard bicycle bearing ball sizes - article comments

Support BikeGremlin

Help BikeGremlin stay online with a Patreon donation:

Not open for further replies.


Staff member
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.

These are the comments from the article:
Standard bicycle bearing ball sizes

This topic is closed for further replies.

If you can't find the answer to your question in this thread, please open a separate thread with your question/problem, in an appropriate forum section (this is the Maintenance and repairs section).

Last edited:
  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.
  2. 57d6be49d5c14e1d62a7b9c898bf9b4a.jpg

    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.
  3. 23d65a2643d3e3691e07c7857408ca8b.jpg

    16/11/2019 at 14:18
    Where to find size of bearings for Fuji S10S 1974 used for the bottom bracket (crank bearings)?
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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.
  4. 65b367bf3d0c83983cc90ffaa71c2758.jpg

    Robert David Taczynski
    24/12/2019 at 19:35
    surface roughness
    egg shapeness
    thought I learned a new word today…wawiness
  5. 5469b3e8225bcdab2df7babcd8998152.jpg

    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.
    • 26f5def97bd49a2a479664baa2df72b5.jpg

      21/07/2020 at 19:44
      3.15mm as measured is likely just to be standard 1/8″ balls, I would have thought…
  2. 7a3af04c36817eebbb5960ac81f08091.jpg

    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 ?
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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).
  3. 839006ee4938aa87599c891ce3ae3994.jpg

    22/02/2021 at 00:57
    Thanks for summing all this up nice and succinctly. Most useful article I’ve read all day!
  4. bd10a96125e7218afa769ea342670350.jpg

    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.
  5. 3ccb0262e583e5c522c9b0a84634d321.jpg

    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?
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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.
  2. bd10a96125e7218afa769ea342670350.jpg

    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
  3. 953a6c05ffcb76f83b9365ccce277d8b.jpg

    23/08/2021 at 11:17
    Thanks Mike and Relja for your replies, I shall discard the cages.
  4. 2c7d61673f0d42e85adfd7c363f0078c.jpg

    29/08/2021 at 00:46
    Good article, but 3/32 is 2.381, not 2.281mm 😉
    greetings from Poland
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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. 🙂
  5. 585e62d1f88b8216e3712812d167d709.jpg

    27/07/2022 at 20:23
    What about stainless steel bearings for hubs? Are they better then regular?
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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
  2. 8e55c26ccb5e8dfd62d110507283658c.jpg

    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!
  3. 49e38d807415ce47a201c5ef5a5d9b2b.jpg

    19/11/2022 at 13:31
    Thanks Relja for taking the time for putting this information together! Very detailed and helpful!
  4. 49e38d807415ce47a201c5ef5a5d9b2b.jpg

    19/11/2022 at 18:03
    Hi Relja
    Would the following be ok for a Shimano rear hub?
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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).
  5. 49e38d807415ce47a201c5ef5a5d9b2b.jpg

    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.
    • 3fd0d771d754ced79ca6b702635900b5.jpg

      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?
This topic is closed for further replies.

If you can't find the answer to your question in this thread, please open a separate thread with your question/problem, in an appropriate forum section (this is the Maintenance and repairs section).

Not open for further replies.


Top Bottom