Bicycle Mechanics - Bottom Bracket Question

My bottom bracket worked itself out about 4mm today on my ride towards the drive side of my bike. I screwed it back in but wonder what caused it to do so? It does not feel as if the bearings are going bad. I took the chain off and spun the crank while holding the seat tube and I felt no grinding or anything to indicate the bearings were going bad.

However, I was doing intervals today and pushing hard and I may not be able to duplicate the stress I put on it by having it on the stand.

Could it be that the lockring was not tight enough? Is there a lockring on your bb?

Could it be that the lockring was not tight enough? Is there a lockring on your bb?

No lockring. It is a sealed BB.

I don't understand why they make bbs without lockrings. I can't answer your question DK, but I can say that if you had a lockring this probably wouldn't be a problem for you. I'm not sure that its advancement to have newfangled cups that you can't lock down.

A lockring on the non-driveside/adjustable cup of a traditional BB is necessary because it is not cinched down, rather it must be screwed in just the right amount for the bearings. Bearing tightness in cartridge BBs are not adjustable by the cups, so there's no need for a lockring. Drive-side cups have no lockring--both traditional and cartridge.

OP: Just tighten it down. By the way, which side was it?

OP: Just tighten it down. By the way, which side was it?

It came out on the drive side. I tightened it down but wonder when it will work loose again?