Originally Posted by
Jamminatrix
Shimano really has two versions of Hollowtech II BB's...the larger diameter (original) ones and the smaller (newer) diameter ones. The older style is still used on lower end models like Sora and Alivio.
The older style larger diameter ones don't last very long because they are sealed like absolute crap. The bearing itself does not have a normal bearing shield pressed between the races, instead relying on a rubber shield sandwhiched between the plastic adapters aluminum cup.
What do you mean by "doesn't last very long"? I have two old style HTII bottom brackets (BB-6700) that have 9,000 and 10,000 miles on them so far and are still in perfect running condition. That isn't 50,000 miles (at least not yet) but it certainly isn't premature failure either.