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Thread: Removing bearings from hollowtech cups

  1. #1
    Senior Member outtacontrol's Avatar
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    Default Removing bearings from hollowtech cups

    Has anyone found a way to easily remove dead bearings from hollowtech cups? I have heard of a tool that does it, but thought you might be able to knock them out from behind.
    When you drink the water, remember those that dug the well.

  2. #2
    swiss cheese udi's Avatar
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    You can do this. First you have to remove the outer plastic shield so you can tap against the inside of the inner race without destroying the shield, a thin flathead around the outside and a some care will get it off in one piece. Below this there is a rubber seal that will just pop off (not part of the bearing, seals against shield), and underneath is the cartridge bearing.

    You can tap the bearing out from behind, but note that on the newer BB's (at least Saint) one side has a lip which is fairly high and difficult to get past. I had no problems with XT ones though.

    Before you go crazy with that though, it's worth knowing that the bearings are a proprietary part - if I remember correctly, a custom 6805 that is narrower on one side and has no seal (or associated lips to hold a seal). Thus you can't legitimately buy / replace the bearings if you want to use the existing custom seal and plastic shield that shimano uses.

    That said, enduro bearings do a kit with their own bearings and seals that you can pop in after you remove all the stock guts.

    Hope that helps.

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    Why bother? A complete new Hollowtech BB can be had for less than $40

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    Do as udi said. A few other points:

    I don't have a proper bike workstand, so to make life a little easier before removing the bearings from the cups, I remove the cups from the bike and stick them in an old (steel) frame that I'm happy to clamp in a vice. It's also easier if you only install the cup you are trying to remove the bearings from, i.e. install one cup, tap out the bearing, remove the now empty cup and repeat for the other side. Before installing the new bearings pop them in the freezer for 15 minutes or so. A little bit of thermal contraction will make it easier to tap them into the cups. Working quickly once you take the bearing out of the freezer. A combination of a rubber mallet, appropriately sized lump of wood and the bearing you just removed will be useful when installing the new bearing. I use Castrol marine grease on the bearing and cup.

    Quote Originally Posted by frensham View Post
    Why bother? A complete new Hollowtech BB can be had for less than $40
    Why endlessly buy stuff you don't need? I don't see having 'do not disassemble' printed on a BB cup as a good reason not to - particularly when it's simple to replace the part that is worn out with a superior one. So yes, it's true, new garden variety Enduro bearings alone will cost the same as a complete Hollowtech BB (if you get one for less than $40). Also the complete BB is easier to install than replacing the bearings in the existing cups, but the replacement bearing will last a lot longer. How much longer? I don't know. I've had bearings in 2 Hollowtech BBs give up after 6-12 months. Both sets were replaced with standard Enduro bearings and are still running fine more than two years later...I think one set is closer to three years old now. On the other hand, buying a new Hollowtech BB every 6-12 months, even for $40 doesn't stack up so well.

  5. #5
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    Have a look at this site - all you need to know including the replacement bearing size:

    http://www.mountainbikerides.co.uk/i...ement&Itemid=9

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    I made up a fairly simple tool to do the job:



    +1 on the enduro bearings. A very worthwhile upgrade.

  7. #7
    Senior Member outtacontrol's Avatar
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    Just knocked the bearings out of 2 sets that I had. 1 was an older style XT, the other a new XT. Both are the external Hollowtech style.

    The older cup was a bit deeper and without measuring, is a bit deeper than the other bearing. Not keen on ordering over the net due to the inconsistent sizing. The link above said 6805 bearing measuring 25x37x7.

    Was thinking of just taking them into a bearing shop to see if they can match one.
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  8. #8
    swiss cheese udi's Avatar
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    I'm fairly sure that link is wrong hey, as I said in my post above it's a custom 6805 bearing that is narrower than a standard one that you would buy at a bearing shop. You can actually use a normal 6805 but the seal and plastic shield will not sit properly because the bearing is too wide, which I'm guessing must have been what the person writing that article did. It still all goes together and works okay.

    Do let us know if you get them matched properly though.

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