Square-taper bottom brackets / cranks are considerably less stiff. If you stand on the arms horizontally (so they are parallel to the ground) and weigh 250lbs, you can actually see the arms flex down.
Octalink / ISIS improves that because of the BB design - the 'notched' design with multiple sides / facets makes it much harder for flex to occur compared to a four-sided design (square).
An external bearing bottom bracket is super stiff: The drive-side crank arm has a spindle permanently attached to it, which attaches directly to the non-drive side arm. This is an improvement over traditional BB's because the BB doesn't serve as a 'middle man' for attachment.
Now, I cannot answer material vs material questions. It would be interesting to see what material holds up with the same BB-type. I'm no material specialist, but I hope that helps!
Originally Posted by
letsthrowfries
I mean, track components are designed for rigidity over weight savings and that's really the heart of what I'm trying to ask, with that in mind are the omniums more attractive because of weight savings or the external bearing bb/stiffness when compared to DA/75/record cranks?
From what I understand, the FSA Carbon's (Track Pro, not Vigorelli) w/ the Platinum Pro Ti BB are close to the same weight as the Omnium's w/ BB. The gain in that instance would be the stiffness from the Omniums. Weights I've seen for Omniums w/ BB are around 850g
Some listed weights that I've seen for D/A for cranks, D/A ring, and D/A BB is right around 700g.
The new FSA Carbon's (Track) uses the same ISIS BB, a Platinum Pro Ti, and the claimed weight for that including a ring is supposed to be
around 650g - which really surprised me to be honest.
Interestingly enough, I have been trying to research this as I'm debating getting some Omniums or keeping my FSA carbon's. Weight or stiffness? To be honest, my wattage output probably won't see any gain in stiffness so I'm probably opting to stay where I am.