Originally Posted by
Leinster
So one overwhelming conclusion is that threadless would work best, if bike manufacturing tolerances were up to spec.
So that leads to the crucial question; what can bike manufacturers change in their processes to match the required tolerance levels? Is there a quick, straightforward fix that can be implemented to carbon mould assemblies, metal welding rigs, etc, that will guarantee that the BB shell is always perfectly round and aligned, and won’t flex under pedaling loads? And if so, why don’t manufacturers implement it?
The simple answer is a steel insert sleeve for CF. Every other application is the outer bearing race is pressed into a steel insert. But that's too heavy, it would add at least 100g likely more, that's massive on a 600g frame.
The next best answer is an aluminum insert. That mostly works, but aluminum is still softer than the steel bearing outer, so it can get deformed during installation and wear. That's essentially what a BSA or T47 BB is.