Originally Posted by
Supercardplayer
Good question I have a 34 tooth cassette on my bike. so you have to good options get a medium cage road derailleur that will work with that cassete just fine . meanwhile my setup is a short cage dearllier with a wolf tooth road link dearlier extender that will work with a bigger cassete. the road link basically makes the derailleur hanger longer. another options is if you're running 9 speed road you can youse a mountain bike derailleur and it will work fine with that cassette if you're running a 9 speed setup. so those are you're options.
Just because it works on YOUR bike with YOUR UNSPECIFIED RDER doesn't mean it'll work on someone else's bike.
RDER hangar geometry can vary between different bikes.
OP already has a MEDIUM cage RDER.
Why don't you specify EXACTLY WHICH medium cage RDER will work?
A 6600 lists a 27T max cog size. VERY unlikely it would even handle 32T, and 30T could be problematic.