Bicycle Mechanics - do sealed bottom brackets need maintenance/repacking? is it possible?
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Please excuse my ignorance, but I took the leap into home maintenance this weekend figuring I would finally make the effort to do that annual repacking of headsets and BB's that are so recommended.
Q2: on removing the BB our of my circa 1994 Spec. Allez (probably 105 but the actual part number was partially obliterated and I've put it back together again now anyway), I was surprised it seemed to be a sealed unit with no obvious way to get at the bearings.
are such sealed units not supposed to need repacking (one book suggests it does) or maintenance?
otherwise, how often should one replace a cartridge BB?
(if it helps, I can remove it and take a picture.)
No repacking of cartridge BBs. Only maintenance is regreasing the cup threads, which I only do if my BB gets creaky.
shimano105 don't have bearings (as a unit, like in a washing machine) but have balls and two cones and two cups, those can be greased if you want, but it's not necessary so often, only when it squeaks.
Bearing units such as truvativ gxp, cannot pe greased or opened, but is very convenient to replace the bearings if it's needed to. Since they are standard bearings 61805 2RS that means 6(balls), 18(load index and external dimension standard), 05 (5*5mm=25mm internal diameter), 2RS(sealed with friction plastic covers at both ends. - but this is not the case, you don't have bearings.
05-10-10, 06:21 PM
Asi, you're thinking of the much older cup and cone setups. Sealed cartridge BB's are a whole other beast. They are a one piece, crimped over setup that you can't get into.
Pstock, I've seen threads here and other links out on the web where some folks just can't accept the idea of "sealed" and have come up with all manner of ways to open up the sealed BB's and re-pack them. But considering that I've typically gotten 7 to 10 years of life from a $25 sealed UN-51 and UN-52 BB's I'd say you can safely ignore them and just make sure the BB shell threads and inner surface are kept lightly greased to avoid any corrosion from water that may get in there.
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