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Rebuilding Campagnolo high-flange Chorus hubs.... bearing confusion

Discussion in 'Bicycle Mechanics and Repairs' started by chriscross1966, 8 Oct 2017.

  1. chriscross1966

    chriscross1966 Well-Known Member

    Location:
    Swindon
    Hi folks,

    I'm about to embark on a rebuild of some high-flange Campy Chorus hubs prior to their installation in my latest project Brompton (yes, I know). As the rear wheel is getting a new axle (it's currently 122mm OLN, I need it to be about 130 to accommodate a 7-speed freewheel) I'm planning on replacing the bearings at the same time. To my feel they're not quite perfect, though they're better than any Brompton hub I've ever touched of course, and might as well do both ends as I'd be stripping the front hub to make sure the grease port pathways is clean as when I got them they didn't have grease port covers. I can get Campy cups and cones pretty cheaply but was wondering what to do regarding bearings.... NOS Campagnolo, name-brand aftermarket side/upgrade, or go off-piste and get some loose ABEC5 Si3N4 ceramics? These aren't going to be intended to be fitted to a daily ride, and if I have my way they will never see a puddle, let alone rain, if only because the bike won't have mudguards. Does anyone have experience of rebuilding the older threaded freewheel Campy hubs in general, and any prior knowledge regarding the bearings would be welcome. Price wise there's not enough in it to make much odds really so that isn't a factor, at the moment I'm tending to go with NOS Campy, but there isn't a lot in it TBH
     
    Last edited: 8 Oct 2017
  2. raleighnut

    raleighnut Guru

    Location:
    On 3 Wheels
    I wouldn't expect the cones to need replacing, let alone the cups. I'd be tempted to stick with Campagnolo bearings though unless you can guarantee the quality of any 'generic' ones.
     
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  3. Yellow Saddle

    Yellow Saddle Veteran

    Location:
    Loch side.
    There's always one true rule of thumb when doing anything on bicycle bearings and that is that ceramic ball bearings are BS. Always. No exceptions.

    Older Campag bearing smoothness was Class 20, Modern Class 10. Just get standard class 20 balls. That's good enough and good enough is good enough.
     
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  4. OP
    OP
    chriscross1966

    chriscross1966 Well-Known Member

    Location:
    Swindon
    OK, Campy or equivalently decent steel it is.. I've got hybrid ceramics in an ultratorque BB on another bike and can't feel any difference between that and the all-steel ultratorque so whilst both are lovely I won't be fitting hybrids to the third UT I have lined up for something else...
     
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  5. You have to look at it logically ... what's the limiting factor in bearing smoothness in this assembly?

    I'd venture that it is very unlikely to be the sphericality of the ballbearings if you use high grade steel ones.

    If you are going to be pressing in new bearing surfaces and potentially refreshing the cones as well, they'll need to "polish in" a bit with use, so initially it'll be the surfaces that will limit the smoothness of the bearing but TBH, any difference is going to be so minor as to not be a factor in any practical way at all.

    Ceramics make some sense (sort of) in very high performance applications if the bearing surface is designed for them

    If the bearing surface is of the right material, you can run oil not grease (since the main reason to use grease is to limit corrosion and with ceramic balls on, say, a stainless surface, there is no corrosion risk to speak of), which reduces the viscous preload on the bearing ... but although the effect is measurable, it's not significant in the context of normal use.

    Hybrid ceramics only really work at all in cases where the bearing surface that the balls are running on is already of exceptional quality ... and so the limitation of smoothness transfers from the bearing surface to the balls. Not many makers *really* have surfaces of that quality and the distortions in surfaces caused by practices like interference fitting can easily put paid to the concentricity and alignment of the bearing components anyway..The bearing components are limited in their performance, in their turn, by the accuracy of manufacture of the seats that the bearing surfaces are pressed into or the accuracy of manufacture of the axle and associated hardware that the cones (in this case) are fitted to and with.

    We used to run track hubs on oil rather than grease in TTs and on the track but that was as much about a psychological advantage for the rider, in the sense that we'd done everything that could be done, than it was abut there being a practical advantage.
     
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    Last edited: 10 Oct 2017