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lol I don't understand any of this, so basically bearings and grease can be replaced on a miche primato pistard rear hub? I took it to the shop and they also said something about closed bearing hub, guess they didn't have the time to look at it yet, but it would be nice to gain some understanding :D
user57774-
'Sealed' bearing hubs have a cartridge bearing that can be serviced to a degree (as above) but generally you would just pop the bearing out and replace it. This type has a shoulder on the axle that the bearing sits against and cone nuts and locknuts to keep everything together.
'Open' or 'loose' bearing hubs have ball bearings which might be in a cage but are not in a cartridge. This type has cones that are tightened to correctly preload the bearings and locknuts to retain this preload. There may be rubber seals (see Shinano mtb hubs) or metal shields to keep out the water and grit or not (see Dura Ace track hubs).
The hubs you have are 'sealed' or cartridge bearing hubs.
The only non-bodgy things you can do to further protect the bearings would be to apply a smear of grease (or Vaseline) to the outside of the bearing or to buy bearing cartridges with better seals (your hubs probably already have rubber shielded bearing cartridges fitted so your only hope would be a better quality of bearing/seal).
Here's a pic of sealed or cartridge bearings with the rubber seals fitted and removed -
As you can see you could flush it with degreaser and relube it but you could not actually get the ball bearings out.
M_V
You could prise the seals out, clean and regressed the actual bearings and carefully replace the seals but luje I said, you can get bearing cartridges for like £1 a time so why bother.