Originally Posted by
BluesDawg
What kind of advantages are you seeking? The Ultegra crank is a bit lighter and stiffer than Tiagra and has a greater bling factor. All of these advantages would be diminished by using the Tiagra chainrings, if that is even possible.
I think he wants to swap the Tiagra and instal Ultregra. I think the Ultegra, from his post, is a compact, whereas the Tiagra is not.