Originally Posted by
vesteroid
I wanted to dig into this, from a general knowledge standpoint (as in I have none, and want to learn) So are you saying that (for instance) an ultegra 175 34/50 crankset will fit both in a bike that was designed with bb30, and the same crackset will fit in a bike with an english BB, and all you need to do is change the BB not the crank?
I can't quite follow your meaning. What I was saying is that if your bike now has a 10 sp Tiagra crank, an Ultegra crank will also fit since they would use the same type of BB, either English or Italian depending on which threading your bike has (probably English). To put either crank into a bike with a BB30 shell would require some kind of adapter which would work with either one. But a BB30 crank will not fit into a frame with an English or Italian threaded BB shell.