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I have a Cube Acid MTB from 2002. It has been used for 45000km, but only during summer on the road, and never in the rain, so absolutely no water on any parts.

Since I will be replacing other parts during the winter break by myself, I was planning on having the LBS to remove the BB so I could find a similar one, and then have them install it before next season.

But I am not sure it is needed. I was just thinking that 45000km sounded like a lot for a BB that has not been serviced for 16 years. The rides the last few months has felt a little bit "muddy", like when you walk in water there is some resistance, but that could be the chain which is a little bit dirty and old (Shimano HG93 XT 27000km).

I have just removed the chain, and when I pull the pedals I do not see any play and when I spin them, I do hear a little bit of noise, but it is more "whoosh" than any creaking or grinding noise, and it does seem to run smoothly.

I do not know exactly what BB is installed but it have to be some standard Shimano. So should I consider replacing it after 45000km in dry conditions or is it possible it can be used for many more miles?

Does anybody have a guess about what BB is installed? I can measure the axle length and diameter, but all this with square tapers and thread, I do not know anything about.

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I would have though that after 18 years and 45000km the bottom bracket would be worn out. I recently learned that bearing wear is heavily dependent on load (source: GCN Everything You Need to Know About Bearings) so if you are a light rider and are not putting out lots of power I guess the bottom bracket bearings could last that long.

If you are not feeling any play in the bottom bracket bearings and they turn smoothly that's further evidence the bearings are OK. If you can you should pull the cranks off and turn the axle with your fingers. You may find you feel drag or 'notchiness' that the mass of the cranks is disguising.

You very likely have a cartridge type bottom bracket bearing unit, these are not particularly expensive and are available from a number of vendors so you may as well replace it. I'd check the chain with a wear gauge and consider replacing it, and look at the chainrings and sprockets as well.

  • I am a reasonable light rider and my average speed is only 20km/h, so I would not say I hammer the pedals much. I will be replacing middle chainring, chain, cassette and pulley wheels, which is why I considered the BB. I do not have any tools for the BB, so cannot check anything further, and while the BB is cheap, it will cost at least $45 to have it removed and then $45 to have the new one installed. – Michael Skov Nov 14 '18 at 15:08
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    Is it really worth it to replace pulley wheels? When mine were worn down the rear derailleur was already in bad shape as well so replacing the full unit made more sense (10€ for pulley wheels vs. ~25€ for a cheap derailleur). The same might apply for the chainring: A new Shimano Deore crankset + BSA bearings costs 65€+10€ and would probably be a considerable upgrade. – Michael Nov 14 '18 at 19:10
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I would see two reasons for replacing a bottom bracket (or any component, actually):

  • the part is worn out and doesn't function properly any more
  • the part is outdated and replacing it with modern version of the part significantly improves your bicycle in the scope of functionality, maintenance or value (or any combination of those)

    The second reason might not apply to retro/vintage bicycles.

I assume your bicycle is not sporting cup-and-cone bottom bracket, it's rather the cartridge bearings type.
Cartridge bearings can be cleaned and re-greased, but once they have some play they need to be replaced (they cannot be adjusted, contrary to cup-and-cone). And again, on some compound bottom brackets you can replace the bearings only keeping your spindle and cups, some are single component with additional (often nylon) cups.

Since we are not sure what type of bottom bracket you have it's difficult to give a specific advice.

Nevertheless, if I was to pay $90 to a LBS for removing and installing a bottom bracket (excluding the cost of the components) I'd rather spent this money on tools and do it myself learning something new at the same time (which I often do).

Since you are not feeling any play or grinding noise, your bottom bracket may be fine. The sounds you are describing may come from the seals on the bearings. Without disassembly it's only an assumption, but on the other hand if it ain't broken, don't fix it.

Should you insist on replacing your bottom bracket, or at least disassembling it to inspect the condition, you can start by posting some pictures of your bottom bracket and asking for some advice on what tools to acquire and how to proceed.

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