Originally Posted by
Iride01
Hmmm.... I just noticed you did say "ultegra 9spd hub". So if it is actually an Ultegra 9 speed FH-6500 hub, maybe you can't just switch the free hub body. There are some differences looking at the parts diagrams.
But there is also the possibility of changing the entire hub and using your old rim. Might not be too much at some shops. Don't know.
The people who have already responded to the thread noted that Shimano does not make an 11 freehub body that will work on their previous hubs.
"Changing the hub" is rebuilding a wheel from scratch with new spokes and is a rather expensive proposition. Better to just buy a cheap 11 speed wheel.