Originally Posted by
10 Wheels
I would pass on it.
With a bum knee your present 9 speed has better gearing.
If you just want to make your 9 speed better, just change the 30T chain ring to a 24T chain ring, which would help your knee going up steep hills.
This is the correct analysis given knee problems are in the mix. Whatever you do, don't give up a three gear front crank for a two. bk