For the first time I'm building a bike, and at the same time rebuilding my first bike. While I'm doing this...I noticed something.

When i took the chain off my old bike and spin the cranks (without pedals) they just keep on spinning with what seems like absolutely no friction at all (I get a few revolutions just from spinning it lightly). When I installed my new bottom bracket / crankset ('05 Ultegra crankset w/integrated BB) on my new frame I need to keep pushing the cranks to keep it spinning. It's not like there's a lot of resistance (I can spin it with my pinky barely pushing) but it doesn't keep spinning like my old BB.

Is this because there's a 'break in period' for BB's? anyone have experience with this?

I know what your talking about, you dont notice it if you are pedaling but by hand just tapping it a bit yea. It does not mean that your BB is crapped out though.

Is your old BB loose bearings type? The Ultegra is a sealed bearing BB and all sealed bearings have a
certain amount of drag from the seals and from the grease packed into the bearing. That is normal.
It will slowly decrease with time but probably never to the point where the BB free wheels. If the
older BB is sealed bearing, that suggests the seals are no longer in contact with the shaft and the
grease is gone from the bearings. Sealed bearings with plastic seals can easily be cleaned and
regreased, the plastic seal pops out with a bit of gentle prying. Metal seals are removable but the
risk of inadvertent damage to the seal is a lot higher. Loose bearing BB with minimal grease will free
wheel as you describe, but when adequately cleaned and lubed they will stiffen up a bit, not as much
as your Ultegra. Steve

I believe on Shimano's better sealed cartridge BBs, like the Ultegra, have seals that keep the water and muck out and are tight enough to have a small amount of drag, nothing of consequence. All the Ultegra BBs I've installed have had a very small amount of resistance when turning them manually.

Put 'em in, torque 'em down and don't worry.

Sweet, glad to hear about the brand new BB not being screwed already.

My old BB is a sealed cartridge, and if it's freewheeling, I probably need to take it apart and re-grease it? Ahh, another project.

Thanks for all the help.

I had a slight bit of resistance and almost a rough rolling feeling when I first installed my FSA Platinum Pro Ti ISIS BB. I was kind of worried at first, but after riding it on the trainer for about 2 hours, it is really smooth now, and spins really quick, with no resistance at all.

I think som e BB's just need a bit of run-in. Sounds stupid, but I think it is true from my own experience.