I have a new sealed bottom bracket, a Shimano BB-UN55. Does it come with lube, and if so what kind of lube would that be?

I assume it's already lubed, because how would you lube it without taking it apart.

There's a little oil on the splines and spindle, but that might just be to keep it from rusting while it's sitting on the shelf.

(This is my first time working with a sealed bottom bracket; up til now it's been all cup-and-cone.)

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    If it's a steel frame you should smear the inside of the frame's bottom bracket housing with heavy grease (taking care to not block the drain holes). – Daniel R Hicks Sep 11 '19 at 23:57

Sealed bottom brackets of the UN-55 type have no serviceable parts. Service consists of replacement. The bearings are sealed. Even if you were able to disassemble it, the seal would be destroyed trying to get more grease into the bearings. I have gone so far as to disassemble one, measure the bearing to find that the part numbers correspond to a standard sized bearing. They are in fact a size only common in bicycle bottom brackets. The good news is that prices seem to be dropping and are readily available for less than $20US.

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Cartridge (and threaded external bottom brackets) come properly lubricated with appropriate grease. Just install in your bike and enjoy.

Cartridge units can’t be disassembled to service the bearings. The seals can be removed on certain external units which allows the bearings to be cleaned and re-lubed.

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