Originally Posted by
miamijim
To keep crud and water from getting into the bearings via the down tube, seat tube and chain stays. Surprisingly a large amount of crud and water works its way into the BB, beer can sleeves are bad option because they dont allow water to drain out the BB shell, that is assuming your BB has a drain hole. Campy sleeves suck for this very reason to, they ride tight agioanst the wall of the BB shell and hold moisture in the tubes thus promoting rust.
Campagnolo has had two designs, one being the two part unit that has a tube with a spigot to fit into the fixed cup and the cone that fits into the adjustable cup and a later one that works on compression of a bellows.
I like the first one for shells with cut outs. The other style works fine for closed shells. A small drain hole is wise for those...
If you want to go gonzo, have a tube machined down like the boss of the engineering company my brother worked for, an "O" ring at each end sealed it up. Be easier just to buy a Phil Wood Bottom Bracket.