Originally Posted by
Bill Kapaun
...
Supposedly, "some" Shimano "road" DER's can handle up to 30T cog, (even though they are rated for a 27T max cog) but it's a bit of a crap shoot.
I've just got a 9 sp 13-30T cassette for my Shimano Ultegra short-cage rear derailler. No problem at all installing and using it. Looks and feels as smooth as the 12-27 it replaces.
Why is it a "crap shoot" ?