I currently have a Shimano Dura Ace FC-7900 crankset with 53/39 chainrings. They have a 5-bolt pattern; does this equate to 110mm? I have been considering using a compact or sub-compact. Can I simply swap out the chainrings and it will shift properly? Will I need to replace the crankset and/or bottom bracket and derailleur? What are my options?