I am currently rebuilding an old steel bike with some modern parts and am searching for a OSPW because it looks quite cool. However a "real" one from CeramicSpeed seems way to expensive for just looking cool. So I checked AliExpress for some cool looking ones and obviously found some. After some research I found out that the main Problem with them is, that the inner bearings are non sealed bearings meaning they get dirty extremely quickly and therefore are not a good upgrade because they probably break before the standard one and cost me more watts than its worth changing them (source for the open bearings is this video here from Trace Velo)

To fix my Problem I was thinking of either adding seals or just saving the ceramic balls and transplanting it into a steal ball bearing housing with seals. Henceforth my Question is firstly: Is this even possible? I am aware that you can rebuild and therefore change parts when you are using cup and cone bearings however I never heard from anyone that they done it with cartridge bearings.Secondly is this feasible and doable without specialist tools and experience?

Thanks for your help

Edit: Weiwen Ng's Answer pretty much sumed it up already. Getting replacement Seals would be quite impossible especially because one of the bearings had nylon races and both had no groves cut out to hold any seals. My other idea of reusing the ceramic balls was proven impossible as well because they where running out of true (probably because the balls aren't really round). I therefore pretty much went with Weiwens idea and just bought new 689 ball bearings with proper seals (I luckily had a small shop specialized in sealing bearings that had cheap bearings available) and pressed them in. That all worked quite nicely and therefore I am now the "proud" owner of an OSPW with fully sealed ceramic bearings for round about 15€. I'll give another feedback when I need to replace the bearings on how long this hack worked out. For now I can just thank everyone who gave his answers/comments to help me with this idea.

  • 1
    Are you just after the look of a large jockey wheel? Could simply fit new cartridge bearings with whatever level of seal you choose. Open has the lowest drag; fully sealed has the most.
    – Criggie
    Jan 14, 2021 at 1:14
  • 2
    Looks like 7-speed Altus to me. Did Shimano poison the market on purpose, or did they think it's a hack that belongs only on second lowest series? Anyway, if you want the lowest possible friction, you don't want sealed bearings. Ceramic balls don't have any measurable benefits on a bike, so standard bearings should be fine.
    – ojs
    Jan 14, 2021 at 8:38
  • 4
    If you just want it for looks, then get the sealed one? job done. From the video, the sealed bearing OSPW performed better after 400 miles anyway than the unsealed ceramic so nothing lost at all by getting a cheap OSPW with sealed steel bearings.
    – Swifty
    Jan 14, 2021 at 9:53
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    @Criggie so the easiest option is to just buy two sealed 689 Bearings (or the specific one for my model) and then switch them? So you wouldn't even bother trying to salvage the ceramic bearings. Is that because it is too mich work to complicated or is there any other reason?
    – Brezelmann
    Jan 14, 2021 at 10:55
  • 3
    For those who didn't know (like me) OSPW = Over-sized pulley wheel
    – Paul H
    Jan 14, 2021 at 18:56

2 Answers 2


While I have no practical experience trying to do this, I doubt that what you propose is easy, and it may not be possible.

Rubber seals require a lip machined into the inner and outer races. This retains the seal. I suppose you could check for a lip. If the bearing were designed specifically as an open (i.e. un-sealed) bearing, which is sensible for a low-contamination environment, then it likely wouldn't have a lip. If it did, you would then have to source a seal with the correct dimensions to fit the lip. There are probably a number of different geometries of seal lips. I don't know the descriptive terminology or important measurements for seal lips and grooves. If you found these out, I expect you'd then have the problem of buying just two pairs of seals - the entities selling those seals probably aren't set up for retail transactions, since really what consumer does this? So, it might be several hundred seals.*

It should be difficult, and it may be impossible, to extract the balls from the cartridge. The balls fit tightly in the races, and in many cases, I suspect they sit in grooves in each race. For example, see the second picture at this link. If you can’t pry the bearings out, you would need to disassemble the cartridge to get at the balls. Furthermore, cartridges aren't designed to be disassembled, so I think this process would be destructive, i.e. you'd need something like a hacksaw. Getting the balls into a new cartridge could require industrial machinery like a hydraulic press. And finally, remember that a bearing series number like 689 just describes the outer diameter, the inner diameter, and the depth. The race thickness can vary - so, thinner race means larger balls and vice versa. You'd need to find two pairs (again, consumer vs industrial scale problem) with all the important dimensions matching your ceramic balls.

Finally, ceramic is relatively hard. I believe that best practice might need you to specify an appropriate race hardness as well (it may be more important in wheel bearings, since as you go over bumps the balls might indent softer steel races). I am not sure how this quantity is parameterized in the industry (i.e. maybe it's Rockwell hardness or something like that, and you need to specify a minimum hardness, and I don't know the appropriate minimum). On another tangent, be aware that the quality of ceramic balls does vary, and I suspect cheap ones are low quality. Plus the quality of the steel used in races also varies, with cheaper races probably having poorer material qualities (probably stemming from more impurities, poorer manufacturing processes) and probably looser tolerances.

This answer is written with no practical knowledge of manufacturing or remanufacturing cartridge bearings. Basically, I learned from a podcast. I could be wrong! And if I am, you should free to let us know. However, hopefully this post has given you some idea of the possible pitfalls you would face.

*I am aware of one company that sells replacement seals for its own bearings: Kogel, which coincidentally makes jockey wheels and bottom brackets with ceramic bearings. Kogel's instructions suggest annual regreasing, which is why they sell replacement seals (although they have communicated to me that if you carefully remove the seal, it's usually reusable). I haven't asked, but I would suspect Chris King sells replacement seals for its bearings, although they have seals that are designed to be repeatedly removed for regreasing. The issue is not that no seals for cartridge bearings can be bought in consumer quantities, it's that you will probably only find seals matched to specific bearings that are designed to be serviced, and this seems like the minority of sealed cartridge bearings.

  • 2
    Good answer. My only comment is that if the bearing has a ball cage, it may be possible to remove and reinstall the cage and balls without special tools. Even when it's possible, it's tedious and really not worth it if you value your time at all, and nobody guarantees that the balls are correct size for different bearing. Don't ask how I know.
    – ojs
    Jan 14, 2021 at 14:19
  • @ojs How do you know this? :-)
    – Weiwen Ng
    Jan 14, 2021 at 15:34
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    I disassembled, degreased and reassembled a cassette bearing in a fidget spinner. With just a dab of silicone oil it now runs really long. I'm so far resisting the temptation to upgrade to ceramic bearings.
    – ojs
    Jan 14, 2021 at 16:13
  • Thanks for the great answer. You outlined pretty much what I was expecting. (but not hoping). However I will try fiddeling arround at least a little bit because I found a small shop near me that sells small bearings like the 689 as single pieces for little money so I can experiment without buying a 100 pieces :-)
    – Brezelmann
    Jan 14, 2021 at 16:14
  • Oh boy, if you try to assemble ball bearings by just ramming all the parts together with a press, you’ll soon find yourself with a pile of shattered metal/ceramic. Take a look at the “construction types” section: en.m.wikipedia.org/wiki/Ball_bearing
    – MaplePanda
    Feb 23, 2021 at 8:35

I assume you mean the bearings from the pulley wheels. You could pry off the seals using a knife or something similar.

I would add low shear grease (such as freehub grease) or oil if you want even less friction.

  • Not quite sure what you mean. I am talking about OSPW from china. They have the problem that they have open (meaning non sealed) ceramic bearings. This is my main problem because that means, that the minute it rains and I use my bike I can throw away these bearings and that is really not how I intend to use my bike. So I am not interessted in reducing friction (especially because open ceramic bearing have almost none) but to make the bearings more reliable and last longer.
    – Brezelmann
    Jan 19, 2021 at 13:51
  • @Brezelmann Friction or seals, you can only choose one.
    – Lien028
    Jan 20, 2021 at 2:59
  • You're right. And well I asked about seals and reliability and if it is possible to reuse/rebuild cartridge bearings and not how to make the ceramics bearings have less friction
    – Brezelmann
    Jan 20, 2021 at 6:52
  • Oh, of course it is possible @Brezelmann . As I mentioned, you can pry of the seals using something sharp. Degrease the bearings w/ your degreaser of choice ( I personally use gasoline since it evaporates quickly) and re-apply grease with a syringe. I wouldn't recommend you do these though, since the seals are normally placed by machines and it is nigh impossible to get the seal to press in perfectly. If there aren't any issues with the bearing, I would just leave it as is.
    – Lien028
    Jan 20, 2021 at 9:16
  • ok so basically instead of trying to reuse the ceramic balls in a new steel housing with the working seals, you'd recommend just replacing the open ceramic bearing with a nicely sealed steel bearing, right?
    – Brezelmann
    Jan 20, 2021 at 9:31

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