Originally Posted by ruppster
I have ran a Tiagra RD on a 32 with no ill effects.
Ability of a RD to handle large cogs depends not only on the type of this particular RD, but also on the shape and length of the derailer hanger. A Tiagra RD on one of my bikes just barely clears the 30T cog with B-tension screw turned to the max; it surely won't handle a larger one.