Originally Posted by
atmdad
What is the purpose of it?
I have one that somehow didn't make it back into one of my bikes about 18 months ago when I cleaned and lubed the BB and I have not been too inclined to want to tear the BB back down.
Have you tried spinning the cranks lately without the chain on? That's how I found out that in spite of my trusted bike mechanic's advice, I'd better get a sleeve, given the grinding sounds I could suddenly hear when the chain wasn't mounted. Luckily, the bearings and all were fine...