Shimano Dura Ace BB 7700 / 7703 differences
I've seen images and descriptions of the 109mm spindle length BB 7700 and it appears to be semi-sealed, i.e. it's an updated version of a cup & cone BB that can be fully dismantled and requires careful cup/locknut adjustment. The cups are connected and sealed with a black plastic middle shell.
I've also seen images of what may be a BB 7703, 118.5mm spindle length, which appears to be a fully-sealed cartridge unit. So I'm wondering if this difference was, for some unknown reason, connected to spindle length, or that there were two different designs pertaining to different years and that the 109mm version also came out as a fully-sealed cartridge BB?
For the 7700-series (9-speed Dura Ace) Octalink bottom brackets the 109 length was for a double crank and was expected to be used for competative racing where very low weight and seal drag was considered important. The 118 mm spindle was for the triple crank and it was assumed low maintenance was more important than the minor weight and adjustability penalty.
For the Ultegra 6500 and 105 5500 9-speed Octalink bottom brackets, both the 109 mm double and 118 mm triple spindles came as fully sealed cartridge units.
Last edited by HillRider; 05-24-12 at 04:25 PM.
Aha, thanks for your help.