Originally Posted by
SlowJoeCrow
If your frame has a 68mm English threaded BB shell and your crank is BB30, then you need something like this
Threaded to 30mm ABEC-3 BB - Black Which is an English threaded external BB with 30mm ID bearings for your BB30 crank. This is a bit kludgy but realtively cheap. The most elegant solution would be to get a 24mm spindle external bearing crankset and bottom bracket like an FSA Gossamer MegaExo, Shimano 105 Hollowtech II or Raceface X-Type. This leaves you buying the crank and BB but you may be able to sell or trade the BB30 part.
That won't work if the crank is actual BB30. BB30 and PF30 use flush press-fit bearings in a standard 68mm width shell with greater than a diameter for the larger bearings that go with the over-sized spindle, and that standard width spindle isn't long enough to accommodate a 68mm BSA shell plus external bearings.
Wider 30mm standards can be made to work - that's the reason behind BB386EVO which pairs with appropriate cups in BSA, BB30, PF30, and other frames. Many newer FSA cranks are BB386EVO and can use the FSA MegaEVO bottom bracket for BSA shells.