How do you tell if a BB is FUBAR, without building a bike?

[Kell]

I'm (STILL) in the process of putting my old 1995 Orange P7 back together.

And when I looked through the box the other day, I wondered about the BB. I've bought a modern replacement (UN50-something) but I still have the UN71/2 from the bike.

Now I don't remember for definite, but I'm almost certain that it was replaced not that long before the bike was retired.

It certainly feels smooth to rotate by hand, but is this a good indicator? Is there a way to tell without building the bike and riding it?

I know it's not a part that will be seen, but it would be nice to keep the period correct one if at all possible.

 

[FSXStumpy]

A few thoughts....

If you have a vice, pad the BB shell with leather and chuck it in the vice. Snug it up. V block is nice to keep it steady. Bolt on a crank arm. Check for play. Check for roughness under load. If tight and smooth, it's a good BB.

I've found that in my "vintage" cartridge bb's, they've had quite short service despite being relatively low mileage, developing crank arm play despite spinning freely... I believe this is because the old grease has hardened and doesn't provide good lubrication. I've taken to using a syringe to add a few ml of heavy weight gear oil to the bearings, by sneaking the needle past the seals. This seems to give'em better life.

J

 

[Kell]

Unfortunately, no vice.

I think I'll (eventually) get around to fitting it and then see.