Shimano BB-UN73 Sealed cartridge - Serviceable?
04-05-21, 01:37 PM
#1
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Shimano BB-UN73 Sealed cartridge - Serviceable?
Hi. I'm doing an overhaul on an old bike and wondering if I should service the sealed cartridge. It's a Shimano BB-UN73. The spindle turns freely but firm. No noise or grinding. I couldn't find any tutorials on how to dissemble this particular unit, otherwise I would just go ahead and do it to be thorough.
Question is, how can I tell if it's good to keep using, and if not, does anyone have any pointer on servicing?
Cheers.
Question is, how can I tell if it's good to keep using, and if not, does anyone have any pointer on servicing?
Cheers.
04-05-21, 01:54 PM
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If it's not rough why would you want to 'service' it? It's generally accepted that when they do start to feel worn/rough you buy a new one. It's not worth most people time to try to take one apart and service it. You'd be replacing bearings that probably cost more to buy than a new bottom bracket.
04-05-21, 02:27 PM
#3
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If it's not rough why would you want to 'service' it? It's generally accepted that when they do start to feel worn/rough you buy a new one. It's not worth most people time to try to take one apart and service it. You'd be replacing bearings that probably cost more to buy than a new bottom bracket.
Cheers
04-05-21, 02:43 PM
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I'm very new to bikes and bike mechanics, so I don't even really know what to look for if it was worn out, besides obvious seizure or grinding. So, answers and advice like yours are what I'm looking for. I'm stripping the bike right down, so I want to service what I can while I'm at it.
Cheers
Cheers
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04-05-21, 03:28 PM
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BB's generally are very inexpensive. They are cheap enough to be considered a consumable. No service, just replace when bad.
I think your BB-UN73 was discontinued and those that have them for sale use that fact to get more money from you than they are worth. But Shimano makes other models that supersede it and are less than 20 bucks.
I think your BB-UN73 was discontinued and those that have them for sale use that fact to get more money from you than they are worth. But Shimano makes other models that supersede it and are less than 20 bucks.
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04-05-21, 08:37 PM
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I have a NIB BB-UN72 left over from years ago and it looks like the outer shell was "turned over" the bearings at both ends, effectively locking them in. You would have to grind off the ends of the shell to free them. As noted, these were not designed to be serviceable and were replaced when worn out, which took a long time. If yours still turns smoothly and quietly, be thankful and keep using it until it doesn't.
