Originally Posted by
yannisg
Has anyone have a rough estimate how long the DuraAce Hollowtech brgs last under normal usage and maintenance.
What model Shimano Dura-Ace BB?
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.
Old:
New:
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.
Mentioned in a post above by HillRider, Enduro makes bearing kits. Enduro claims the extended life comes from larger diameter bearings withstanding load forces better, but that isn't the case (as Shimano went to even smaller bearings on the new BB's, which disproves this). The longer life with the Enduro kits actually comes from the fact the Enduro kit has real seals which do a much better job of keeping water/debris out.
The newer, smaller diameter Shimano BB's seem to be shielded slightly better than its predecessor.