Originally Posted by
cyccommute
You just need the proper bottom bracket for the square taper. The external bearings thread into the bottom bracket shell of the bike with the same thread pitch and direction as a cassette bearing.
You can't use the external bearings, however. Different system, diameters and spindle length.
So if I understand you correctly (I haven't looked at Madone frame in a year), the external bearing cups thread into the
inside of the bottom bracket. So the square taper bottom bracket I'm currently running just needs to be removed from my Allez and should screw into the Madone frame no problem.
(just assumed some sort of backward incompatibility (e.g., external cups having external bottom bracket threading) had been designed in by the manufacturer)